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807 Cards in this Set
- Front
- Back
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What does a neuron consists of?
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Cell body (AKA soma or perikaryon) - contains cell's nucleus and organelles
Neurites - project from soma |
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What are the two types of neurites?
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Dendrites and axons
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What do dendrites contain?
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Receptors to receive chemical signals from other neurons
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How do dendrites increase area available for signal reception
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By tapering distalling and branching extensively
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What is a dendritic tree
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The dendritic branches of a single neuron
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What is the axon
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Singular projection that may extend very far
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Axon hillock?
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Where axon forms
Small elevation from soma |
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What is the initial segment of axon?
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Follows hillock
Uninsulated portion of axon that is rich in voltage-gated sodium channels |
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What is an axon terminal?
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At end of axon
AKA terminal bouton Form synapses with other neurons or effector structures |
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How is information transmitted within the neuron?
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As an electrical signal
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How is information transmitted between neurons (synaptic transmission)
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As a chemical signal
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How does the action potential travel?
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Along the cell membrane from the initial segment to the axon terminal
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What are glial cells?
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AKA neuroglia
Supporting cells of CNS More numerous than neurons |
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What do glial cells do, as a group?
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Regulating chemical milieu in EC space
Maintain suitable environment for neuronal function Myelinate neurons Phagocytosis Repair in the case of injury Lining fluid filled ventricles of brain |
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What are the major divisions of the CNS?
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Brain:
Cerebrum Cerebellum Brainstem Spinal cord |
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What is the CNS?
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Primary processor of sensory info and executor of responses
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How much cardiac output does the brain receive?
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15-17%
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How much oxygen does the brain consume?
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20% of body oxygen
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What do rostral, caudal, ventral and dorsal mean, above the brainstem?
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Rostral - toward front of brain
Caudal - toward back of brain Ventral - toward bottom of brain Dorsal - toward top of brain |
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What do rostral, caudal, ventral, and dorsal mean, in brainstem and spinal cord?
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Rostral - toward cerebrum
Caudal - toward bottom of spinal cord Ventral - toward front Dorsal - toward back |
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How are tracts named?
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According to their:
Origin (neuron cell body) and termination |
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Where is the corticospinal tract?
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Connects cerebral cortex with spinal cord
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Afferent?
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Conducting toward structure
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Efferent?
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Conducting away from structure
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What does the cerebrum do?
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Performs more complex processing of sensory information
Formulates volitional motor responses Sensations must reach the cerebral cortex in order to be consciously perceived |
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What does the cerebrum consist of?
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Diencephalon
2 cerebral hemispheres containing: Gyri (ridges) Sulci (furrows) |
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What is the cerebral cortex?
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Laminar structure forming outer surface of cerebrum
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Ventricles of cerebrum?
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Internal fluid filled spaces
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What are groups of nuclei within the CNS called?
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Nuclei
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What is gray matter?
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Gray color due to cortex and nuclei being rich in neuronal cell bodies
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White matter
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Areas under the cortex that is rich in myelinated axons
Collections of tracts/fasciculi |
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What are 2 primary white matter structures in the cerebrum
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Corpus callosum - major pathway for axons crossing between the cerebral hemispheres
Internal capsule - major pathway between cerebral hemispheres and more caudal structures |
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What is the purpose of gyri and sulci
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Increase surface area of cerebral cortex within cranium
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What are fissures?
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Deeper and more consistent sulci
Primary fissures divide cerebrum into lobes Cortical areas of similar function are located near each other |
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CSF?
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Secreted within ventricles
Circulates out of the ventricles over surface of brain and spinal cord and empties into bloodstream through venous sinuses Floats the brain within the cranial cavity and protects from trauma |
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Thalamus
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Cerebrum major nuclear group
Key to regulation and processing of somatic information Major relay and processing center for sensation and motor function Switchboard for almost all brain activity Is part of the diencephalon |
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Diencephalon
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Thalamus
Hypothalamus Epithalamus Subthalamus |
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Hypothalamus
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Primary brain center for autonomic NS regulation
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Basal ganglia
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Cerebrum
Group of nuclei involved in motor processing Associated structures: Caudate nucleus Putamen Globus pallidus Subthalamic nucleus Substantia nigra |
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Hippocampal formation
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Cerebrum
Located in the medial temporal lobe on each side of the brain Involved in consolidation of memory |
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Cerebellum
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Consists of:
2 hemispheres vermis (midline structure) Attached to posterior aspect of brainstem More convoluted surface than cerebral cortex Uses complex sensory information to unconsciously modulate motor activity |
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Brainstem
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CNS interface for cranial nerves (PNS)
1st order processing of primary sensation, including special senses Has tracts between spinal cord and brain Neurons for both somatic motor and parasympathetic (autonomic) output Acts like primitive brain - controls respiration, HR, other autonomic functions |
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Divisions of brainstem
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Midbrain
Pons Medulla |
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Midbrain
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Rostral most part of brainstem
Contains nuclei for eye movement control through: CN III CN IV |
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Pons
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Contains major nuclei for communication between cerebrum and cerebellum
Nuclei for: CN V CN VI CN VII CN VIII |
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Medulla
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Caudal most part of brainstem
Major nuclei for consciousness (reticular formation), autonomic control Nuclei for: CN IX CN X CN XI CN XII |
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Spinal cord
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Primary point of interface for CNS with body via peripheral nerves
Sends and receives information from brain via collection of axons (tracts) Contains neurons that: Receive primary somatic sensory information Directly and indirectly modulate motor activity of muscles Modulate autonomic activity of viscera |
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What are the major nuclear groups in the cerebrum?
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Thalamus
Hypothalamus Basal ganglia Hippocampus |
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What do the meninges consist of?
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CT membranes that surround the CNS
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What are the meninges continuous with?
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The CT of peripheral nerves
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What are the primary layers from the skull inward to the brain?
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Dura
Arachnoid Pia |
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What are the meningeal sinuses (dura) essential for?
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Venous drainage of the cranial cavity
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What does the circulation of CSF depend on
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Meningeal structures
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What form compartments in the cranial cavity
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Meningeal septa
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What do the meninges develop from?
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The neural crest and mesoderm
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When do they meninges surround the NS
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Between 20-35 days of gestation
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What becomes the dura?
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Ectomeninx
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What becomes the pia and arachnoid
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Endomeninx
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When do the meninges have the adult pattern?
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By the end of the 1st trimester
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What is the term for the pia and arachnoid
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Leptomeninges
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Dermal sinus defect
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Often associated with spina bifida
Usually in lumbar area, in congenital dermal sinus Ectoderm fails to completely dissociate from neuroectoderm Epithelium lined channel to surface of skin Can result in recurrent meningitis |
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What does the ectomeninx around the brain do?
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Stays attached to the periosteal CT layer
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What does the ectomeninx in the spinal cord do?
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Initially continuous with periosteum during development but later separates to leave epidural space
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What is another name for the dura mater
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Pachymeninx
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What do the meninges consist of?
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Fibroblasts
EC collagen |
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What is the arachnoid attached to?
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Dura
Separated from pia by subarachnoid space Attached to pia with arachnoid trabeculae (CT tissue strands) |
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What is in the subarachnoid space?
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CSF
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What layer is closely adherent to the surface of the brain and spinal cord tissue and surrounds surface vessels on the brain
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Pia mater
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What are the divisions of the dura mater?
What is the most distinct boundary? |
Periosteal part
Meningeal part Border cell part Most distinct boundary is between dural border cells and meningeal dura |
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What does the dura contain large amounts of?
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Collagen, in the periosteal and meningeal layers
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What do patterns of collagen play a role in?
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Cranial mechanics
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Dura mater structure
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Dural border cell layer with arachnoid mater contains matrix with no dense CT matrix of periosteal and meningeal layers
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Where is there a plane of weakness in the meninges
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Between dura mater and arachnoid mater
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Subdural hematoma
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Bleeding into plane of weakness dissects dura and arachnoid planes
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What may happen when the brain is removed from a cadaver
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the arachnoid may split away from the dura at the dural border
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Dural septa (infoldings)
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Consist of areas in which the meningeal portion of the dura folds in to separate cranial cavity into compartments
Compartments determine how displacements can occur with injury |
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Primary folds
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Falx cerebri
Tentorium cerebelli Falx cerebelli Diaphragma sella |
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Falx cerebri - where is it and what are its attachments
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Lies in longitudinal fissure
Attaches anteriorly to crista gali Attaches posteriorly to tentorium cerebelli |
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Tentorium cerebelli
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Lies axially in the transverse fissure connecting to the anterior clinoid processes
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Falx cerebelli
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Lies in midline of cerebellar hemispheres to varying heights
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Diaphragma sella
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Forms roof of hypophyseal fossa encircling the infundibulum
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Compartments formed by dural septa - what separates the lateral supratentorial and infratentorial compartments
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Lateral supratentorial compartments separated by falx cerebri
Infratentorial compartment bordered by tentorium cerebelli |
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What do the rigid dural structures do
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Limit expansion of cranial contents to compartments
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What can an expanding mass do
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Push contents betweeen compartments
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What are dural sinuses
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Venous structures formed by separation of meningeal and periosteal dura at edges of dural septa
Also form at the free edges of dural septa from 2 layers of meningeal dura |
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Where does the blood filling the dural sinuses collect from
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Connecting veins from the cortical surface and internal structures
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Vascular supply for dura?
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Runs between periosteum and periosteal dura, often in grooves on skull
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What can skull fractures cause
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Disruption of dural arteries, producing dissection of the connective tissue layers and an epidural hematoma
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What parts of the brain can feel pain
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The dura can
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What innervates the anterior and middle cranial fossa
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Branches of the trigeminal nerve
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What innervates the dura of the posterior fossa
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Sensory branches from C2 and C3 (also C1 when present)
May have sensation through vagus |
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What innervates the tentorium
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The tentorial nerve (a branch of the opthalmic)
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Irritation of nerves in the dura
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Produces pain appearing to originate in affected region according to afferent nerve innervation
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Headache from dura above tentorium
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Innervation by trigeminal nereve
Irritation referred to face |
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Headache from infratentorial dura
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Innervation by cervical nerves
Irritation referred to back of head |
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Dural headaches and neck
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Connection between dura and neck muscles
Muscle tension and dural stimulation by contraction |
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What is the arachnoid mater
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More delicate membrane
Attached to the dura |
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Parts of arachnoid mater
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Arachnoid barrier layer
Arachnoid trabeculae |
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What do the arachnoid trabeculae do
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Suspend the brain in the subarachnoid space
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What is the subarachnoid space
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Where CSF flows
Between the arachnoid barrier layer and the pia on the surface of the brain |
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Arachnoid villi
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Specializations of the dura arachnoid interface in dural sinuses
Allow drainage of CSF into venous system Essential for CSF circulation and normal intracranial pressure |
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What are collections of arachnoid villi called
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Arachnoid granulations
May calcify in old people and be called pacchionian bodies |
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What is the pia mater
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Delicate covering that is closely adherent to the brain
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What are the layers of the pia mater
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External epipial layer
Intima pia layer |
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Intima pia layer
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Close to glia limitans or glial basement membrane that forms the outermost layer of cerebral cortex
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Where is the pia thicker
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Spinal cord
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What covers most surface vessels on the brain in the subarachnoid space
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Pial or leptomeningeal cells
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What is the small EC space that the pial layer may follow ***
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Virchow-Robin space ***
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What do the pial coverings and spaces allow
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Better exchange of CSF
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Where can leukemic cells enter brain parenchyma
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??
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Epidural space
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In spinal cord
Epidural anasthetics |
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What does the absence of a dural attachment to the vertebrae allow
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Allows the dura to stretch as vertebra move
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What permits the neurological signs (Kernig and Brudzinski) that are used to indicate meningitis
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Stretching of the spinal dura or resistance to stretch
Dura's attachments to nerve roots |
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What is the spinal cord dura anchored to
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To the spinal column indirectly through the exits of the spinal roots and the filum terminale externum that connects the end of the dura to the coccyx
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Specialized attachment elements in the spinal cord of the pia mater
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Denticulate ligaments
Filum terminale internum |
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Filum terminale internum
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Attaches to caudal end of dural sack that makes up lumbar cistern
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Denticulate ligaments
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Attach from the spinal cord pia arachnoid to the spinal dura at 21 pairs of points between the foramen magnum and the first lumbar spinal nerve
Consist of pia arachnoid Attach to dura at points midway between nerve exits |
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What do the denticulate ligaments and the filum terminale do
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Further help stabilize the spinal cord relative to the dura and spinal column
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What is the primary subarachnoid cistern associated with the spinal cord meninges
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The lumbar cistern
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What is the lumbar cistern
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The extension of spinal meninges (usually L1-L2) after the end of the spinal cord
Contains cauda equina and is the space commonly accessed in spinal taps (L3-L4) |
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What are meningiomas
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Tumors of the meninges that can form space occupying lesions that compress the brain in dural compartments
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What are meningiomas most likely to arise from
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Clusters of arachnoid cells in the villi (arachnoid cap cells)
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Where are meningiomas most likely to form
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At points where cranial nerves or blood vessels transverse the dura, along the base of the skull and at the cribiform plate
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Who is most likely to present with meningiomas
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Women aged 55 - 70
Patients with neurofibromatosis |
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What kind of meningioma is most common
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Benign or atypical
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Benign or atypical meningiomas
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Located outside the brain parenchyma
Rarely penetrate brain tissue Neurological signs are generally due to compression or edema May become large before detection (b/c usually in anterior fossa) |
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Bacterial meningitis - initial location
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Usually initially located in and spread through subarachnoid space
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What does bacterial meningitis usually involve
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arachnoid and pia
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What does the CSF look like with bacterial meningititis
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Cloudy with many WBCs, increased protein, and bacteria
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Symptoms of acute bacterial meningitis
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Fever
Alternating chills and fever Headache Depressed consciousness |
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What happens due to thickening of the meninges in bacterial meningitist
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Partial obstruction of CSF return flow
Signs of increased intracranial pressure |
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Viral meningitis
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Caused by a variety of agents
Younger patients Usually only supportive treatment |
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What are examples of electrical synapses
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Gap junctions
Connexons Electrotonic synapses Ephaptic connection |
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What are electrical synapses
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Modifications of membranes between 2 adjacent cells that allow a direct transfer of small molecules
Not specific to nervous tissue or electrically excitable cells In NS - most common b/w glial cells |
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What are the 2 primary types of electrical synapses
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Ephaptic connections
Gap junctions |
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Ephaptic connections
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area of low resistance (ion channel) contact can allow exchange of ions between cells
In NS - most common among astrocytes |
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Gap junctions
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AKA electrotonic synapses
Small regions closely apposed cell membranes containing channels comprised of 1 connexon from each cell |
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What is a connexon
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Symmetric component - mirror image of the other
Comprised of hexamers of connexin subunit molecules |
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What are gap junctions formed by connexons permeable to
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Ions (Na, K, Ca) and small metabolites up to 1,000 MW
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What does a short half life of connexons suggest
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Functional plasticity
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What selectivity to gap junctions show
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Ionic and directional selectivity in some cases (cations versus anions) and may also open and close in response to large voltage differences between cells
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What can gap junctions create
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Regions of cells of similar electric potential or other metabolic characteristics (syncytium)
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Where do typical gap junctions occur
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Between astrocytes, oligodendrocytes, Schwann cells in PNS, cells of meninges, ependymal cells lining ventricles, and between cell types
Also participate in control of capillary beds |
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What pathological conditions might gap junctions participate in
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Cerebral edema
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What is the role of gap junctions in embryonic development
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Help define synchronous development of groups of cells
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What do gap junctions allow in neurons
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IC electrical coupling - may accompany chemical synapses
Allows very rapid transmission of information Appears to contribute to organized oscillatory or rhythmic activity of nuclei such as inferior olive, phrenic nucleus, eye movement nuclei |
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What are other arreas with gap junctions
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Olfactory bulb and hypothalamus
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Some pathologies with gap junction role
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Seizures
Spreading depression Migraines |
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Charcot-marie-tooth disease
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Related to mutations in gene for connexons
Results in demyelination and slowing conduction in peripheral axons with subsequent muscle weakness, atrophy, and sensory loss |
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Chemical synapses
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Use of chemical substance to convey electrical activity and sometimes other info
Require electrical signal (AP) to be converted to chemical signal (neurotransmitter releasE) and then back to an electrical signal (post synaptic potential) Slower, less reliable than electrical and more susceptible to toxins, but allows more complex processing |
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3 primary elements of chemical synapses
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1. presynaptic element (bouton)
2. synaptic cleft 3. postsynaptic element |
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Polarity of transmission
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Seen in chemical synapses
From the presynaptic specialization to the postsynaptic membrane |
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Sequence of neurotransmission
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1. Presynaptic bouton -
Vesicle synthesis and loading with transmitter and the transport to the synaptic terminal Depolarization of the terminal and release of NT into synaptic cleft 2. postsynaptic membrane - binding of the transmitter to and activation of a receptor Transduction of the signal by the postsynaptic cell 3. Pre and post synaptic - Reuptake or degradation of NT |
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Electrical to chemical transduction
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In presynaptic terminal - accomplished by vesicular release of neurotransmitter
Incoming AP or depol. opens voltage sensitive calcium channels |
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Vesicle fusion and transmitter release
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Increase in Ca initiates vesicle release through mechanism involing docking of synaptic vesicles to protein complexes ( t&v snares)
Fusion of vesicle membrane with active zone on presynaptic terminal (fusion proteins - synaptophysin, docking proteins) |
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Electrical to chemical transmitter release
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Release of NT into synaptic cleft is controlled through calmodulin and Ca sensitive protein, synaptotagmin
Transmitter then diffuses across the synaptic cleft to bind to receptors on post synaptic membrane |
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Vesicle recycling - what proteins are involve
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Vesicle membranes are recycled through a process involving dynamin and clatharin
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What kinds of NTs can be released from varicosities through axons and how
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Catecholamines and neuropeptides
Through diffusion and into EC space Autonomic axons (usually symp) can use this or it can be non-synaptic |
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Processing of small molecule neurotransmitters within presynaptic terminals
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E.g. AAs, biogenic amines
Undergo extensive recylcling and synthesis within presynaptic terminal Makes them potentially sensitive to agents that interfere with synthetic or recycling enzymes within the temrinal E.g. ACh |
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Processing of large molecule NTs
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E.g. neuropeptids (> 10 C atoms, substance P)
synthesized in GA and transported via fast axoplasmic transport to nerve terminal Released and degraded but not usually recycled |
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Chemical to electrical diffusion and receptor binding
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After release into the synaptic cleft, NTs diffuse across the synaptic cleft and contact receptors on the post synaptic membrane
Receptors and their reaction define the nature of the transduction back to electrical signal |
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Receptor activation in chemical synapses - reactions
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Direct opening of ion channesl
Cascade of biochemical reactions |
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Classification of receptor activation and postsynaptic response by function
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Ligated channels - open or close transmembrane pores or channels
G protein coupled and other second messenger receptors Transmembrane receptors with modifiable enzymatic activity Ligand dependent regulators of nuclear transcription Sequestration of IC ions |
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Ionotropic synapses
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Usually includes small molecule synapses, fast synapses, single messenger synapses
Activate primarily ionotropic receptors |
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Metabotropic synapses
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Usually includes larger neuropeptide synapses, slow synapses, 2nd messenger synapses
Activate primarily metabotropic receptors Can also be mixed as more than 1 NT that can be released or a single transmitter may activate multiple types of receptors |
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Activation and result of ionotropic synapses
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Easily activated (NT releaseD)
Their binding to ionotropic receptors (ligated ion channels) in postsyn membrane opens an ion channel to depolarize or hyperpolarize the postsyn membrane |
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Metabotropic synapses
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The post synaptic receptors activate an enzymatic cascade to produce a 2nd messenger that produces an actual transduction event
Result may include opening of ion channels and depol of cell but can include induction of broad ranging metabolic changes in post syn cell that can alter its sensitivity or activity |
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What is the advantage of the metabotropic synapses
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Ability to magnify the transduction and regulate postsynaptic cell
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What do 75% of metabotropic receptors initiate transduction through
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G proteins:
NT binding to receptor allows coupling of the receptor to a G protein Forms complex with enzyme system that generates 2nd messenger |
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What can G proteins act as
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2nd messengers, and can do things such as opening ion channels
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Most common 2nd messenger systems
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Adenylyl cyclase - produces cAMP as 2nd messenger --> phosphorylates proteins
Phospholipase C - produces phosphoinositol and DAG as 2nd messengers --> release Ca stores Phospholipase A - initiates arachidonic acid cascade All can amplify a postsyn response by enzymatic means depending on cell sensitivity |
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NT inactivation
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After NT is bound to receptor it must be inactivated in some manner to prepare for the next signal
Binding of NT to receptors is reversible and NT is released to diffuse away Then the NT is rapidly removed from synaptic cleft by 2 primary mechanisms: inactivation and reuptake |
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Inactivation mechanism
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Molecule is destroyed or modified by membrane bound enzymes around cleft (can be on postsyn membrane, adjacent astrocytes, or presynaptic membrane) that typically cleave the transmitter into smaller inactive but recycleable parts
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Reuptake mechanism
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Most NTs or their products are directly taken up by transporter proteins on presyn membrane and on adjacent neuroglial cells
Some can be taken up by pinocytosis in which vesicles with the contents of the cleft are formed from the presyn membrane |
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Catecholamine reuptake
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dopamine and norepi are inactivated by MAO and catechol-o-methyl trandferase
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Non neuronal receptors and transmitter metabolism
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receptors are on neuroglial cells too and they can modulate the neuroglial control of the synaptic environment including neuroglial inactivation and recylcing of NTs and balance of ions
Astrocytes active for GABA and glutamate |
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Other forms of synaptic communication
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Presynaptic receptor - mediated autoregulation (autoreceptors and heteroreceptors)
Retrograde transmission |
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Retrograde transmission (neuromodulation)
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Process of feedback from postsynaptic cell
Postsyn cell responds to synaptic activation by releasing a 2nd chemical messenger capable of affecting the presyn nerve terminal or neuron Ex: NO |
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Presynaptic autoregulation
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Receptors are on presynaptic membrane for same NTs that it releases or other substances that are released from vesicle at same time (ionotropic or metabotropic)
Receptors can modulate NT synth, release, reuptake and package Usually inhibitory May be retrogradely transported to produce metabolic effects Ex: Autonomic regulation of SA node |
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Receptor regulation
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Receptors can be regulated through a number of mechanisms that can act over time
Changes in receptors will regulate the responsiveness of the cell to subsequent exposure to the NT of agonist substance Generally metabotropic |
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Receptor densensitization
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Sensitivity of receptors may be affected over short period of time by chemical mod.
Binding of NTs may make receptor vulnerable to actions of IC enzymes that will modify the receptor Phosphorylation may either change the binding or transduction properties of the receptor to make it less efficient |
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Homologous desens.
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Desensitization produced directly from process of receptor activation
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Denervation supersensitivity
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Ex of upregulation
Loss of neuronal contact with a cell --> cell synthesizing and exposing more receptors cell becomes supersensitive |
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AA NTs
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Glutamate
GABA Glycine |
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Biogenic amine NTs
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ACh
monoamines - catecholamines (dopamine, epi, norepi) serotonin histamine |
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Neuropeptide NTs
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VIP
Substance P enkephalins endorphins orexin oxytocin vasopressin |
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Purine NTs
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Adenosine
ATP |
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Gaseous NTs
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NO
CO |
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Glutamate
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Most prevalent excitatory NT in CNS
Derived from aKG by GABA transaminase Recycled by direct transporter into presyn terminals for reuse and indirectly through astrocytes where it is degraded to glutamine and then reconverted to glutamate |
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GABA
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Primary inhibitory NT in brain
Found in high amounts in striatum and lentiform nuclei, hypothalamus, hippocampus, periaqueductal gray Transmitter for purkinje fibers in cerebellum Synth from glutamate by glutamic acid decarb. Similar recycling to glutamate |
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Glycine
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Inhibitory NT mainly in brainstem and spinal cord
Associated with mechanisms of recurrent inhibition (in spinal cord renshaw cells) Part of inhibitory mechanism common to motor neuron pools to limit activity Recycled through active transporter |
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ACh
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Important NT in both CNS and PNS
Both excitatory and inhibitory with both metabotropic and ionotropic receptors Synth from choline and acetyl CoA by choline acetylase Broken down by acetylcholineesterase to choline nd acetic acid which are both recycled into terminal and recycled |
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Catecholamines as NTs
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Both excitatory and inhibitory
Synthesized from tyr ins teps to create dopamine, epi, norepi Most enzymes of synth are modifiable Diverse functions - motor function (dopamine), reward/addiction behavior and sleep/waking cycles Bind to numerous receptors (CNS and PNS) both presyn and post. Major inactivation enzymes are COMT in postsyn membrane and MAO in presyn terminal cytoplasm |
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Serotonin
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excitatory and inhibitory
Synth from trp by trp hydroxylase and 5 HT decarb. Functions in sleep/wake, emotional behavioral states and vasoconstriction ASsociated with actions of many hallucinogens Broken down by MAO or transported back into presyn terminal |
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Histamines
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Excitatory
Synth from histidine by histidine decarb Also component of mast cells and basophils (vasodilation) and involved in gastric secretion Associated with sleep/wake cycles and maintenance of consciousness Broken down by histamine N methyltransferase and diamine oxidase |
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Neuropeptides as NTs
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Ex: substance P, enkephalins, VIP
All metabotropic and G protein coupled Release is often non synaptic or as co transmitter Prominent in hypothalamus, centrally (oxytocin, vasopressin) with major roles in autonomic function Also found in basal ganglia and brainstem Substance P, enkephalin, b-endorphin are all involved in transmission of pain and pleasure sensations, their regulation and central affect |
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What is the longitudinal fissure
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Separates the L and R cerebral hemispheres
Contains falx cerebri |
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What is the lateral fissure
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Sylvian fissure
Separates temporal lobe from frontal and parietal lobes |
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What is the transverse fissure
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Between cerebrum and cerebellum
Tentorium is here |
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What is the central sulcus
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fissure of rolando
Separates frontal and parietal lobes, specifically the precentral and postcentral gyri |
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What is the parieto-occipital sulcus/fissure
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Divides the parietal and occipital lobes on the medial surface of the hemisphere from the upper end of this fissure to a small depression called the preoccipital (parieto) notch defines the border laterally
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Frontal lobes
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Largest
Motor and cognitive functions primary motor cortex is here Front of brain, anterior to central sulcus, above lateral fissure |
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Parietal lobes
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Sensory - associative function
INcludes primary sensory cortex Behind central sulcus, above lateral fissure, and in front of occipital lobe |
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Occipital lobes
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Visual and visual association function
Back of cerebrum, behind parieto-occipital fissure and imaginary line between top of this fissure and the preoccipital notch |
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Temporal lobes
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Integrative sensory, some functions of memory, audition and olfaction
Inferior to lateral fissure, rostral to occipital lobe |
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Insular lobe
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triangular shaped, invaginated cortical area hidden in the depths of the lateral fissure
Mixed function, sensory and motor |
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Limbic lobe
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Synthetic lobe on the medial aspect of the hemisphere which encircles corpus callosum and medial part of the temporal lobe
Involved in emotion Primary processor of memory |
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What is the main function of the spinal cord
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Forms the primary interface between the PNS and the CNS
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Where is the spinal cord
|
Within the vertebral canal extending from foramen magnum to L1-L2 disc
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Relationship between spinal cord and vertebral column during development
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Vertebral column outgrows spinal cord during development
During 3rd month of dev. the cord fills the vertebral canal Caudal end of the spinal cord is located at L3 in the newborn |
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What is white matter and how does it stain
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Collections of axons
Funiculi Tracts Fasciculi Appears black b/c myelin stains |
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What is gray matter
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Cell bodies - unstained
Surrounded by white mattee |
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What is the spinal cord formed from
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Caudal portion of neural plate with formation of neural tube
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What happens after neural tube closure
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Neuroepithelial cells in ventricular zone begin to divide and form neuroblasts and glioblasts
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What cells form the future neurons and neuroglial cells of spinal cord
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Neuroblasts and glioblasts
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What happens to the proliferating neuroblasts
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Migrate to form a layer that contains most of the neuronal cell bodies of the spinal cord, the intermediate or mantle zone
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What becomes spinal cord gray matter
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Intermediate, or mantle zone
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What does the mantle zone develop into
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Under the influence of special secreted proteins, it becomes 4 distinct dorsoventral columns of cells on each side, the alar and basal plates
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What separates the alar and basal plates
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Sulcus limitans
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Where does white matter develop
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In marginal zone
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What is the marginal zone
|
A layer of neuroblast processes that forms outside of the mantle zone of the neural tube
Processes of neurons formed in brainstem and forebrain also contribute |
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What else does the marginal zone contain
|
Developing glial cells (Astrocytes and oligodendrocytes) that will form the structure of the spinal white matter and eventually myelinate the long tracts of the spinal cord in pre and post natal dev.
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What becomes the dorsal horns
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Dorsal horns are sensory associated spinal neurons
ARise from alar lamina |
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What becomes ventral horns
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Ventral horns are motor associated neurons
Arise from basal lamina |
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What do the 4 columns of cells do
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Estbalish basic sensory-dorsal/motor-ventral organization of neurons in the adult spinal cord
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What forms between the alar and basal plates
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An intermediate zone
Originates from components of both alar and basal plates and evenetually contains neurons that have both motor and sensory neurons (Clark's column, origin of spincerebellar tracts) |
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What is the central area between the horns
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Intermediate gray commisure
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Ventricular zone
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Cells lining ventricular zone that persist into later dev. form ependymal cells that line central canal
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What is the central canal
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Begins at 4th ventricle in lower brainstem
May or may not have a patent lumen over the entire length of the spinal cord |
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What are the enlargements of the spinal cord
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Cervical - C4-T1
Lumbosacral - L1-S2 |
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What extend longitudinally along the surface of the spinal cord
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Grooves
Sulci Fissure |
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Anterior median fissure
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Penetrates deeply into the cord, extending almost to the middle
Contains sulcal branches of anterior spinal artery |
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Anterolateral sulcus
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Where ventral roots leave the cord
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Posterolateral sulcus
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Marks site of entry of dorsal roots (dorsal root entry zone)
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Posterior median sulcus
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In midline on dorsal aspect of cord
Contains delicate pial partitiion - posterior median septum |
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Posterior intermediate sulcus
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In upper thoracic and cervical spinal cord
Lies between the psoterior median and psoterior lateral sulci Partially divides the dorsal columns |
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What accompanies the entry and exit ofaxons into and out of the spinal cord
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Change in the type of cell myelinating the axon
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Where do oligodendrocytes myelinate
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myelinate axons up to their exit from or entry into the spinal cord
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What does myelination outside of the spinal cord
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Schwann cells
Peripheral myelination Has important effects on the ability of these axons to regenerate after lesions |
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What forms each spinal nerve
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Merger of dorsal adn ventral roots at particular spinal level
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What is the portion of the spinal cord that gives rise to a spinal nerve
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Segment
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Which nerves may lack a dorsal root contribution
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C1 and CO1
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How are spinal cord segments and nerves identified
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According to the intervertebral foramen through which the spinal nerve (dorsal and ventral roots) exit the vertebral canal
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Where do spinal nerves C1-C7 pass
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Above the same numbered vertb
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Where does spinal nerve C8 emerge
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between C7 and T1 vert
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Where do spinal nerves below C8 pass
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Below the same numbered vert
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What is a dermatome
|
An area of skin that is innervated by dorsal roots arisng from a single spinal cord segment
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What is a myotome
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The skeletal muscle that is inenrvated by motor fibers arising from a single spinal cord segment
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How does the spinal nerve carry information
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Bidirectionally - between spinal cord and body
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GSA
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Neurons in DRG convey info from receptors in skin, muscle, tendons, and joints
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GVA
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These nerve fibers are from mechanoreceptors and nociceptors within the viscera. Cell bodies within DRG as well
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GSE
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axons arise from motor neurons within the spinal cord (ventral horn) and innervate body musculature involved in volitional motor activity
Single neuron pathway from spinal cord to muscle |
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GVE
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Axons of neurons within the spinal cord that terminate in autonomic ganglia ie sympathetic and parasympathetic ganglia
Postganglionic neurons then innervate smooth muscle, cardiac muscle, and glands. 2 neuron pathway |
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Where does the dura mater extend
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From foramen magnum down to S2
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what separates the dura mater from bone of the vertebral canal
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Epidural space - contains fat, loose CT, and internal venous plexuses.
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Where and why are local anesthetics injuected
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Injected into epidural space to anesthetize the lumbar and sacral spinal nerves during operative procedures and for post op pain control
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What is the arachnoid mater (spinal cord)
|
delicate, avascular
Conforms to inner aspect of dura (unless pathology - then subdural space) Contains cells joined by tight junctions that serve to form a barrier against fluid and substances crossing the membrane |
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What do arachnoid trabeculae do
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Extend through CSF filled subarachnoid space to pia mater below
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What are the 2 specializations of the pia mater
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Denticulate ligs and filum terminale
Both stabilize spinal cord |
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Where are denticulate ligs
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Fibrous band of pia on each side of the spinal cord between ventral and dorsal spinal roots
Usually 21 on each side |
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What is the filum terminale internum
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thin thread of pia mater that arises from the caudal end of the spinal cord, the conus medullaris and travels inferiorly to caudal tip of thecal sac at S2
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Lumbar cistern
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Expansion of the spinal subarachnoid space caudal to conus medullaris
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Filum terminal externum
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Continuation of pial thread that pierces through thecal sac and extends caudally
Pia becomes enclosed by dura which attaches to coccyx |
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What is the subdivision of the gray matter
|
Divided into rexed laminae based on size, shape and distribution of neurons
10 laminae in all |
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What laminae is the dorsal horn composed of
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Laminae I-VI
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Wwhat is the intermediate zone composed of - what lamina
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Lamina VII
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What is the ventral horn composed of - which laminae
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Laminae VIII-IX
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What lamina surrounds the central canal
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Lamina X
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Lamina I and Lamina V
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Lamina I (posteromarginal nucleus) and lamina V receive nociceptive input via lightly or unmyelinated small diameter afferents
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Laminae III and IV
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Laminaee III and IV (nucleus propruis) receiive non-noxious input via myelinated, large diameter afferents
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Lamina II
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Lamina II (substantia gelatinosa) receives input from nociceptive afferents (C fibers) and collaterals from large diameter afferents
Site of 1st order processing Contains interneurons that can modulate pain transmissoin |
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Lamina VI
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Lamina VI (base of dorsal horn) receives input from descending motor pathways and proprioceptive input from the periphery
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Nucleus dorsalis of Clarke
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AKA clarke's column
FOund in dorsal medial part of lamina VII at spinal segments C8-L2 |
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What does the nucleus of the intermediate zone do
|
Receives proprioceptive input from muscle and sends axonal projections to the ipsilateral cerebellum (dorsal spinocerebellar tract)
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IML
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Found in spinal segments T1-L2 in small lateral horn of intermed zone
These neurons give rise to pregan sympath efferent fibers |
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Sacral autonomic nuclei
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Found laterally in lamina VII in segments S2-S4
No lateral horn here. These neurons give rise to pregang parasymp fibers that exit the spinal cord via ventral roots to form pelvic nerves |
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what does the ventral horn contain
|
Groups of interneurons that coordinate the activation of motor nueron pools
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Lamina VIII
|
Contains primarily interneurons although some found in lamina IX
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what do motor interneurons do
|
Relay and integrate segmental and descending inputs to motor neurons
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Lamina IX
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Main somatic motor area of spinal grey matter
Contains large alpha motorneurons and smaller gamma motor neurons that innervate skeletal muscle and associated intrafusal fibers and muscle spindle organs, respectively Largest in cervical and lumbar spinal cord |
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Phrenic nucleus
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Located centrally in ventral horn of C3-5
Provide motor innnervation to diaphragm via phrenic n Respiration may be affected if this motor nucleus is disturbed with spinal cord injury |
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Spinal accessory nucleus
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Contains motor neurons that innervate the SCM and trap
IN ventral horn from C1-C5 |
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Neurons that innervate flexor mm
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Locate dorsally
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Neurons that innervate extensor mm
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Found ventrally
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Neurons that innervate trunk mm
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Found medially
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neurons that innervate extremity mm - where are they in the gray matter
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Laterally within ventral horn
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What are the motor neurons and interneurons of the ventral horn innvervated by
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Descending motor pathways
Involved in local reflex ciecuits |
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Area-lamina X
|
receives afferents conveying visceral pain related info
Neurons from this lamina project to higher center via dorsal columns |
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What are reflexes
|
Automatic motor responses to sensory stimuli applied to the periphery and transmitted to CNS
Stimulus connects centrally through dorsal roots to activate some muscles and inhibit others - occurs through innervation of excitatory or inhibitory interneurons that then innervate motor neuron pools to supply the muscles |
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Simple spinal reflexes in spinal cord
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Can operate in absence of higher centers
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Crossed extensor reflex
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Reflexes that cross the midline
Activation of extensors contrallateraly to support the body on other side when leg is removed |
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Intersegmental reflexes
|
Reflexes may be modulated across spinal segments rostro-caudal
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Muscle spindles
|
Attached parallel to skeletal muscles (extrafusal)
Contain specialized muscle fibers (intrafusal) that detect static and dynamic properties of stretch in extrafusal m |
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What do muscle spindles do
|
Detect change in muscle length and rate of stretching of muscle
Output travels through dorsal roots into the spinal cord, where activation or inhibition of groups of motor neurons that control muscle activity may occur |
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Nuclear bag fibers
|
Detect dynamic aspects of stretch (Speed, rate of change in muscle length) and action potential discharges increase as a muscle is stretched
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Nuclear chain fibers
|
Produce increased action potentials primarily with changes in muscle length
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|
Tendon reflex
|
A rapid stretch of the muscle by tapping a tendon will activate both dynamic and static aspects of muscle spindles
Through spindle connections, muscle spindle output is used to cause a reflex contraction of the same muscle, while the opposing muscle groups are inhibited via interneuron connections |
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Monosynaptic reflexd
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Direct connections to motor neurons (alpha motor neurons)
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Gamma motor innervation
|
Contractile portions of muscle spindles are innervated by gamma motor neurons and can beused to adjust the tension or sensitivity of the muscle spindle as the muscle shortens during contraction
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Gamma activation
|
Activation of muscle spindles by gamma motor neuron contraction of the spindle can be used to control contraction of extrafusal muscle
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What might contact gamma motor neurons and how is it useful
|
Descending tracts such as corticospinal tract might
useful in control of muscle tone (tension) in postural mm (mostly unconscious) |
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GTOs
|
form inhibitory counterpart to muscle spindles
are nerve endings near MT junction |
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What activates a GTO
|
Strong stretch of a tendon during contraction activates GTOs of DRG neurons
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What do GTO DRG neurons do
|
Activate inhibitory interneurons that in turn inhibit alpha motor neurons
Effect is to prevent strong contractions that could damage the muscle |
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What are tracts (fasciculi)
|
How the white matter is organizeed
|
|
|
Gross subdivision of white matter
|
3 paired regions called funiculi
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|
Dorsal funiliculus
|
Between dorsal root entry zone (posterolateral sulcus) and posterior median septum
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Lateral funiculus
|
Between dorsal root entry zone and site where ventral roots emerge from spinal cord (anterolateral sulcus)
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Ventral funiculus
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Between anterolateral sulcus and anterior median fissure
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Anterior white commisure
|
At dorsal end of anterior median fissure
Major pain pathway - neurons that contribute to anterolateral system cross here |
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Blood supply of spinal cord
|
Anterior and posterior spinal aa
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Ant spinal - what does it originate from
|
Originates from vertebral aa
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Post spinal artery - what does it originate from
|
Originates from posterior inferior cerebellar aa
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What supplements the anterior and posterior spinal arteries
|
Segmental arteries that include radicular aa that follow the dorsal and ventral roots and spinal medullary aa that directly and indirectly join the ant and post spinal arteries from the aorta
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|
Arterial vasocorona
|
Formed by the anastomosis of arteries around the spinal cord
|
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|
What supplies spinal grey matter
|
Central branches of the anterior spinal artery
Includes most areas of the ventral and intermediate horns |
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What supplies the posterior sections of the dorsal horn
|
Posterior spinal artery
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|
What do most vascular lesions that directly affect motor neurons involve
|
Anterior spinal artery
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Why are deficits from posterior spinal artery infarcts lesions less likely
|
Because there is more collateral cirulcation from redicular and medullary arteries
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Ascending tracks
|
Carry information from spinal cord to brainstem and forebrain
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Descending tracks
|
Carry information from forebrain and brainstem to spinal cord
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|
Propriospinal axons
|
Form the local circuitry for the spinal cord (intersegmental reflexes, etc)
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|
Long trracts
|
Tracts that carry information between the spinal cord and the cerebrum or brainstem
Primary ones: Corticospinal Posterior column - medial lemn anterolateral spinocerebellar hypothalamospinal |
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Corticospinal tract
|
part of pyramidal system
Includes corticobulbar fibers volitional motor |
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|
Posterior (dorsal) column medial lemniscal system
|
Discriminative (epicritic) touch
Vibration sense Proprioception |
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Anterolateral system
|
Spinothalamic
Spinomesencephalic Spinoreticular Pain temperature crude (protopathic) touch |
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Spinocerebellar tracts
|
Anterior and psoterior
Unconscious proprioception Info from muscles to cerebellum |
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Hypothalamospinal system
|
Central control of preganglionc autonomic neurons in spinal cord
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Pyramidal system
|
Major source of volitional motor control
Neurons of origin in cerebral cortex including primary motor cortex and related areas in frontal lobe but also some sensory areas Sends projections to brainstem (corticobulbar, aka corticonuclear) and spinal cord (corticospinal) |
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|
How is motor control via the corticospinal tract accomplished
|
Through 2 types of neurons:
Those in motor cortex of brain & Motor neurons in spinal cord |
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What are the motor neurons of the pyramidal tract called
|
Upper motor neurons - have their origin and termination within the CNS
|
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What are the spinal cord and brainstem motor neurons called
|
Lower motor neurons
Originate in CNS but terminate in periphery |
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|
Which component of the pyramidal system projects to the spinal cord
|
corticospinal tract
|
|
|
What is the major descending pathway from the brain to the spinal cord
|
Corticospinal tract
|
|
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Where do axons of the corticospinal tract originate
|
2/3 of them originate from neurons in motor cortex (frontal cortex and precentral gyrus)
1/3 originate from sensory areas (primary sensory cortex and parietal areas) - modulate sensory input and terminate in dorsal horn of spinal cord |
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What do most corticospinal axons do
|
Cross midline at level of foramen magnum to descend in dorsal part of lateral funiculus on the contralateral side (LSCT)
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|
What happens if one side of brain's motor control is injured
|
The opposite side of the body is affected
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What do the minority of corticospinal axons do
|
Do not cross - form anterior corticospinal tract which descends ipsilaterally in spinal cord in ant funiculus
Axons partilally cross the midline at spinal level at which they innervate motor neurons and interneurons |
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|
What tract primarily innervates axial musculature
|
Anterior corticospinal tract
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|
|
Corticospinal tract innervation
|
Most of innervation is via interneurons
Generally excitatory to flexors and inhibitory to extensors Primary function is control of fine skilled movements in extremities |
|
|
How is the corticospinal pathway organized
|
Somatotopically
Axons for leg areas are generally lateral in the tract to those that innervate the trunk or arm, which will be medial |
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|
Other descending motor tracts
|
Arise from neurons in brainstem
Rubrospinal vestibulospinal reticulospinal |
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|
Rubrospinal tract
|
originates in red nucleus of rostral midbrain crossing midline near its origin
primary function is facilitaiton of flexor activity in arm and forearm and some inhibition of extensors |
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|
Extensor biased descending systems
|
Vestibulospinal
Reticulospinal |
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|
Reticulospinal tracts
|
Originate from nuclei in brainstem reticular formation and travel in ventral and ventral lateral funiculus
Influence primarily motor neurons supplying paravertebral and limb extensor mm Involved in less conscious activitie like muscle tone related to posture |
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|
Vestibulospinal tracts
|
Originate from the complex of vestibular nuclei that receive the input of the vestibular portion of the vestibulocochlear nerve in the brainstem
Facilitate extensor mm and act to maintain posture |
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|
Primary input for vestibulospinal tracts
|
Vestibular apparatus
Cerebellum Cerebellum uses info conveyed by spinocerebellar tracts and vestibular sensory inputs to control posture partly through vestibulospinal tracts |
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|
Upper motor neuron influences for visceromotor activity
|
Hypothalamus
Brainstem |
|
|
In a Free Speech Essay question, what do you do if the speech the statute is regulating is Content Neutral (Time, Place, Manner Regulation – statute exists regardless of the message)?
|
In a Free Speech Essay question, what do you do if the speech the statute is regulating is Content Neutral (Time, Place, Manner Regulation – statute exists regardless of the message)?
If content neutral regulation of time, place, manner –then apply a 3-party test. The regulation must: [1] further a significant government interest (noise, crowd, or litter control; traffic safety); [2] Be narrowly tailored (no more restrictive than necessary), and [3] leave open alternative channels of communication (commercial door-to-door solicitation w/o invitation of the homeowner may be restricted b/c other avenues of communication exist such as the mail, newspaper advertisements, radio, and television) |
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|
Major pathway for viscermotor pathway
|
Hypothalamospinal tract - ipsilateral pathway
|
|
|
Ascending systems
|
Primary ascending divisions:
Dorsal columns Anterolateral system spinocerebellar tracts |
|
|
Dorsal columns
|
Consist primarily of central processes of DRG neurons
Carry discriminative (2 pt, fine, epicritic) touch, vibration, position sense and kinesthesis Axons are myelinated, fast conducting (type Ia, Ib, II, and A-beta) and enter spinal cord in medial division of DR entry zone |
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|
How is dorsal column info carried
|
Ipsilaterally
Fasciculus gracilis (medial) Fasciculus cuneatus (lateral) |
|
|
What separates the fasciculus gracilis and cuneatus
|
Posterior intermediate sulcus
|
|
|
Fasciculus gracilis
|
Consists of axons of DRG neurons below T6
|
|
|
Fasciculus cuneatus
|
Contains axons of DRG neurons above T6
|
|
|
How are the axons in the dorsal columns organized
|
Somatotopically
Afferents from foot and leg are medial while arm and neck are laterally (trunk in betwene) |
|
|
Where do dorsal column axons synapse
|
In nucleus gracilis and cuneatus
|
|
|
What is the medial lemniscus
|
A tract formed by axons from nucleus gracilis and cuneatus when they cross the midline at the level of the obex (medulla)
Continues through brainstem to thalamus then thalamic neurons project to sensroy areas of cerebral cortex |
|
|
Anterolateral system
|
A collection of tracts including:
Spinothalamic SPinomesencephalic Spinoreticular Carry protopathic sensation (pain, temp, crude touch) Sensations are conveyed by unmyelinated and finely myelinated axons (type III, IV, A-delta, and C) that enter the spinal cord in the lateral division of the DR entry zone Tracts run largely in the lateral and partly in ant funiculi of spinal cord |
|
|
Sensory info in anterolateral system
|
Arrives primarily in lateral division of DR entry zone
|
|
|
Where do axons of anterolateral system synapse
|
Mostly in lamina IV of dorsal horn
|
|
|
How does anterolateral system reach somatosensory cortex
|
Through more direct route with thalamus as its 1st major connection and indirect route through reticular formation collaterals
|
|
|
How are sensations carried by anterolateral system affected by lesions
|
They are resistant to disruptions by lesions because collaterals are given off to some local areas
|
|
|
Anterior spinothalamic tract
|
Carries protopathic touch
|
|
|
Lateral spinothalamic tract
|
Carries pain and temp
|
|
|
What do the spinocerebellar tracts carry
|
Unconscious sensation from receptors (muscle spindles, joint capsule receptors, skin)
Info used by cerebellum to program coordinated muscle activity |
|
|
How is sensory info condducted in spinocerebellar tracts
|
Through DRG to cell nuclei in intermediate zone of spinal grey matter or adjacent areas and then to cerebellum
|
|
|
Major divisions of spinocerebellar tracs
|
Anterior and posterior spinocerebellar
Cuneocerebellar tract at cervical and brainstem levels |
|
|
What do the anterior and posterior spinocerebellar tracts do
|
Carry sensroy info from lower limb to cerebellum
|
|
|
What does the cuneocerebellar tract do
|
Carries information from upper limb to cerebellum
|
|
|
Paths of spinocerebellar tracts
|
Posterior and cuneocerebellar ascend to cerebellum iipsilaterally and carry info from individual mm
Anterior crossses in spinal crod and ascends to cerebellum contralaterally but eventually recrosses in cerebellum. Carries info integrated for whole lower limb |
|
|
What blood supply for funiculi of spinal cord
|
Posterior and anterior spinal arteries
|
|
|
What is the blood supply to the dorsal columns
|
Posterior spinal artery
|
|
|
What is the blood supply to the ventral and alteral funiculi
|
More medial regions by anterior spinal a
Lateral regions around border by posterior spinal artery and arterial vasocorona |
|
|
What is the basic principle of neuromodulation
|
To either change the frequency or amplitude of synaptic transmission
Endogenous/physiological neuromodulation or Exogenous/therapeutic neuromodulation |
|
|
Examples of endogenous/physiological neuromodulation
|
Regulation of NT release at nerve endings: autoreceptors and heteroreceptors
|
|
|
Regulation of NT release at nerve endings: autoreceptors and heteroreceptors
|
?
|
|
|
Too much norepi
|
Anxiety
panic anorexia excitability insomnia |
|
|
Too little norepi
|
Depression
ADD/ADHD |
|
|
Too much dopamine
|
Psychoses
Tourette's chorea |
|
|
Too little dopamine
|
Parkinson's
ADD/ADHD Depression |
|
|
Too much ACh
|
Delirium
Confusion Psychoses |
|
|
Too little ACh
|
Alzheimer's
|
|
|
Too much serotonin
|
Sleep
Hallucinations Decreased appetite Anxiety |
|
|
Too little serotonin
|
Depression
OCD Pain sensitivity Anxiety |
|
|
Too much glutamate
|
Seizures
Neuronal degeneration |
|
|
Too little glutamate
|
Schizophrenia
Depression Cognitive impairment |
|
|
Too much GABA
|
CNS depression
resp depression sedation |
|
|
Too little GABA
|
Seizures
Movement disorders |
|
|
Goal of exogenous or therapeutic neurmodulation
|
Restore/correct any chemical inbalances that cause clinical symptoms
|
|
|
NTs that act via ionotropic receptors
|
Glutamate (AMPA/K)
GABA(a) ACh (nicotinic) Glycine Serotonin (5-HT3) Purines |
|
|
NTs that act via metabotropic receptors
|
Glutamate (mGluRs)
GABA(b) ACh (muscarininc) Dopamine (D1 and D2) Serotonin (5HT1, 5HT2) Norep, Epi (alpha and beta adr) Histamine All neuropeptides Adenosine (A1, A2) |
|
|
Post synaptic effects of ACh
|
Excitatory
Arousal Short term memory Learning |
|
|
Postsynaptic effects of norepi
|
Excitatory
Arousal Wakefullness Mood CV regulation |
|
|
Post synaptic effects of dopamine
|
Excitatory
Emotion Reward systems |
|
|
Post synaptic effects of serotonin
|
Excitatory
Feeding behavior Control of body temp Modulation of sensory pathways, including: Pain Regulation of mood/emotion Sleep/wakefullness |
|
|
Postsynaptic effects of GABA
|
inhibitory
Mediates majority of inhibitory postsynaptic potentials |
|
|
Post synaptic effects of glycine
|
Inhibitory
Increases Cl- flux into postsynaptic neuron, resulting in hyperpolarization |
|
|
Post synaptic effects of glutamate
|
Excitatory
Mediates excitatory Na+ influx into postsynaptic neuron |
|
|
Post synaptic effects of substance P
|
Excitatory
Mediates nociception within spinal cord |
|
|
Post synaptic effects of met-enkephalin
|
Inhibitory (generally)
Mediates analgesia as well as other CNS effects |
|
|
Common mechanisms by which neurotransmission can be altered
|
Alter NT synthesis
Alter NT reuptake and recycling Alter NT degradation Alter NT release Activate or block NT receptors Alter postsynaptic signal transduction |
|
|
Drugs that target ionotropic receptors
|
Nicotine
Benzodiazepines Barbiturates Ethanol Anti-epileptics Anesthetics |
|
|
Drugs that target metabotropic receptors
|
Anesthetics
Analgesics opiates Hallucinogens Anti-parkinsons Antipsychotics |
|
|
Drugs that target NT transporters
|
Tricyclic antidepressants
SSRIs Stimulants |
|
|
Drugs that target enzymes
|
Anti-parkinson's
Antidepressants Lithium Alzheimer's |
|
|
Strategies used for increasing NT synthesis
|
Increase the availability of NT precursors
|
|
|
Strategies used for decreasing NT synthesis
|
Block one or more of enzymes involved in synth of the NT
Provide false precursor leading to formation of inactive or dummy NTs |
|
|
Catecholamines and modifying synthesis
|
?
|
|
|
Synthesis promotion dopamiine
|
By providing a precursor, L-dopa that can enter the brain and get converted to dopamine, the levels of dopamine in nerve terminals and its release can be enhanced
|
|
|
Disruption of NE synthesis
|
Inhibition of tyrosine hydroxylase (e.g. Metrysoline)
False precursor leading to formation of dummy transmitters (e.g. methyldopa) Blockage of vesicular transporter (e.g. reserpine inhibits dopamine uptake into vesicle) |
|
|
Inhibition of NT reuptake
|
Tends to increase the levels of NT in synaptic cleft and prolong the effect of the NT
|
|
|
What is the fastest way to end the NT action in the synaptic cleft
|
Reuptake process
|
|
|
Reuptake I inhibitors
|
Cocaine and amphetamine have general effects of inhibiting the reuptake of monoamines
|
|
|
SSRIs
|
In diseases like depression there is a functional deficit of monoamines like serotonin and NE
SSRIs block serotonin reuptake, thereby prolonging its action |
|
|
TCAs and SNRIs
|
?
|
|
|
Inhibition of NT degradation
|
Increases synaptic concentrations of NTs
Ex: MAOIs for monoamines COMT inhibitors Cholinesterase inhibitors for ACh |
|
|
MAOs and COMTs
|
slide 26
|
|
|
Metabolic degradation of catecholamines
|
After being taken up into the presynaptic terminal, NE, dopamine and serotonin are degraded by MAO (mt enzyme)
|
|
|
What do MAOIs do
|
Prevent degradation of NTs in cytoplasm and promote their transport into synaptic vesicles for subsequent release
|
|
|
What do COMTs do
|
Inactivate NE, epi, dopamine, in extrasynaptic tissue
|
|
|
Non-selective MAOIs
|
Inhibit both MAO-A and MAO-B
Increase availability of all monoamines Ex: tranylcypromine, phenelzine |
|
|
Selective MAOIs
|
MAO-B inhibitor Selgeline treats Parkinson's disease
|
|
|
COMT inhibitors (ex)
|
Entcapone (used in Parkinson's disease)
|
|
|
What do Selgeline and entacapone do
|
Increase availability of dopamine at synapse
|
|
|
Synthesis, release and degradation of ACh
|
1. synthesis of ACh
2. uptake into storage vesicles 3. release of ACh 4. Binding to the receptor 5. degradation of ACh 6. Recycling of choline |
|
|
What inhibits transport of choline
|
Hemicholinuim
|
|
|
What inhibits release of ACh
|
Botulinum toxin
|
|
|
What can cause release of ACh
|
Spider venom
|
|
|
Consumer Law: When are plaintiff's attorneys fees awarded? How much?
|
DTPA mandates that a prevailing consumer be awarded court costs and rsbl and necessary atty fees. The award is mandatory, but the amount is discretionary.
DTPA attorney fees must be awarded in a dollar amount based on amount of work performed by attorney (i.e. hourly basis), regardless of fee agreement (% contingency fee is valid, but the amount of attorney fees awarded will be applied to the % the attorney is entitled to recover under the agreement). |
|
|
Neostigmine
|
Used in treatment of myasthenia gravis
Prolongs the life of ACh in the synaptic cleft to compensate for the reduced number of ACh receptors at the NM junction |
|
|
Organophosphates
|
Irreversible inhibitors of cholinesterase
ACh accumulates in synaptic cleft and causes prolonged depolarization of skeletal muescle making it less sensitive to additional ACh release Death from respiratory paralysis |
|
|
What can decrease NT release
|
Blocking calcium entry into depolarized presynaptic nerve terminal via N-type Ca channels
Block synaptic vesicle fusion with presynaptic membrane |
|
|
What can block synaptic vesicle fusion with presynaptic membrane
|
Tetanus toxin
Botulinum toxin |
|
|
What do conotoxins do
|
Directly block Ca channel pore
|
|
|
Botulinum toxin
|
Irreversibly blocks release of ACh at NM junctions and at autonomic terminals
Affects both smooth and skeletal muscle Patients have weakness initially in muscles innervated by cranial nerves and then in limbs Dry mouth, abdominal cramps, vomiting, diarrhea b/c of absence of peristalsis |
|
|
Botox
|
Chemical denervation
Nerve terminals fully disrupted by Botox must regrow or sprout locally for function to be restored |
|
|
Activation or blockade of receptors
|
In presynaptic receptors - NT release properties may be affected
Postsynaptic receptors - will affect the responses of the postsynaptic cell alone |
|
|
Receptor agonists
|
Mimic the action of a NT at a receptor
|
|
|
Receptor antagonist
|
block the action of the NT at the receptor level
|
|
|
Excitatory AAs
|
Glutamic acid or Glutamate
Aspartate |
|
|
Inhibitory AAs
|
GABA
Gly |
|
|
Ionotropic glutamate receptors
|
Essentially ligand gated channels
AMPA Kainate NMDA |
|
|
Metabotropic glutamate receptors
|
G protein coupled receptors
Group 1 Group 2 Group 3 |
|
|
Group I mGluRs
|
mGluR 1,5 activates PLC
|
|
|
Group II mGluRs
|
mGluR 2, 3 inhibits adenylate cyclase
|
|
|
Group III mGluRs
|
mGluR 4,6,7,8 inhibit AC
|
|
|
Ionotropic glutamate receptors
|
slide 38
|
|
|
Overstimulation of NMDA receptors
|
Thought to cause degeneration of neurons (high levels of intracellular Ca)
|
|
|
Memantine
|
NMDA antagonist
Slows the rate of memory loss in Alzheimers |
|
|
Modulation of excitatory neurotransmission by GABA
|
slide 40
|
|
|
Drugs that act at GABA(a) receptor
|
Picrotoxin
barbiturates Biculline Benzodiazepines Ethanol |
|
|
Drugs that act at GABA(b) receptor
|
Baclofen (lioresal) a muscle relaxant (GABAb agonist)
|
|
|
Alteration of signal transduction
|
Very few drugs
Viagra is 1 |
|
|
How does viagra work (sildenafil)
|
Prolongs the duration of NO via indirect mechanism that inhibits phosphodiesterase5 to block the breakdown of cGMP
|
|
|
Blockers of action potential propagation
|
Voltage gated sodium channel blockers can be blocked and thus AP propagation blocked
Ex: lidocaine, antiepileptics - carbamazepine, phenytoin, valproic acid |
|
|
What kind of drug is lidocaine
|
Voltage gated Na channel blocker
|
|
|
What kind of drugs are antiepileptics
|
Voltage gated Na channel blocker
|
|
|
What are common antiepileptics that act as voltage gated Na channel blockers
|
Carbamazepine
Phenytoin Valproic acid |
|
|
Synthesis of catecholamines
|
?
|
|
|
Basic functions of brainstem
|
Control of respiration
HR contains nuclei for most CNs contains tracts cerebrum and all caudal structures and major connections for cerebellum |
|
|
Where is the brainstem
|
Extends from caudal diencephalon (primarily thalamus) to the spinal cord at level of foramen magnum
|
|
|
Divisions of brain stem
|
Midbrain
Pons Medulla oblongata |
|
|
Ventricular systemw
|
Series of interconnected ependyma-lined cavities in CNS
contains CSF |
|
|
Ventricular structures in the brain stem
|
Cerebral aqueduct
Fourth ventricle |
|
|
Where is the cerebral aqueduct
|
In midbrain
|
|
|
Where is the fourth ventricle
|
Between the pons/medulla and the cerebellum
|
|
|
Where is CSF secreted
|
primarily in lateral ventricles (also in 3rd and 4th) by choroid plexus and circulates into 3rd ventricle
|
|
|
How does CSF flow
|
Through cerebral aqueduct to midline 4th vntricle and subsequently into subarachnoid space through 3 foramina leading out of 4th ventricle
|
|
|
What surface of the brainstem is associated with the 4th ventricle
|
rhomboid fossa
|
|
|
What are the primary surface markings of the rhomboid fossa
|
Median sulcus
Obex |
|
|
What is the obex
|
Site of 4th ventricle closure and beginning of central canal of spinal cord
|
|
|
Where is the midbrain
|
extends from pons (superior pontine sulcus) to the mamillary bodies of the diencephalon anteriorly
|
|
|
Anatomical boundaries of the midbrain
|
Dorsally bounded by tectum, from posterior commisure rostrally to the caudal inferior colliculus
|
|
|
A. Tectum
|
Consists of 2 pairs of bumps, the superior colliculli and inferior colliculi that are together called the quadrigeminal plate
a division of the midbrain |
|
|
Superior colliculus
|
laminated structure (7 layers) related to visual pathways
coordinates reflexes to visual stimuli and contributes to the control of eye movements |
|
|
Inferior colliculus
|
major nucleus forming a relay station of the auditory pathways from the cochlea to cerebral cortex
coordinates reflexes to auditory stimuli |
|
|
B tegmentum
|
area containing nuclei and fiber tracts ventral to the cerebral aqueduct, including periaqueductal gray, CN nuclei for CN III and IV, and the red nucleus
many major pathways b/w the brain and brainstem or spinal cord pass through division of midbrain |
|
|
basilar area - what does it contain
|
contains crus cerebri, a major efferent pathway from cerebral cortex to brainstem and spinal cord
|
|
|
crus cerebri
|
bundle of descending tracts originating from the cerebrum
|
|
|
What is the interpeduncular fossa
|
Space between peduncles on the ventral surface of the midbrain
|
|
|
What does cerebral peduncle mean
|
All of the midbrain on each side, exclusive of the tectum
|
|
|
What separates the crus cerebri from the midbrain teguntum
|
the substantia nigra
|
|
|
What forms the only path of communication between the 3rd and 4th ventricles
|
the cerebral aqueduct
common site for bloackage of CSF |
|
|
What cell bodies are contained in the midbrain
|
cell bodies for CN III and IV which both modulate contraction of extraocular muscles
|
|
|
Where does CN III emerge
|
from interpeduncular fossa
|
|
|
Where does CN IV emerge
|
dorsally, just below the inferior colliculus
|
|
|
What is the pons dervied from
|
the rhomencephalon
|
|
|
Where is the pons
|
Ventrally - between superior and inferior pontine sulci
dorsally - contributes to floor of 4th ventricle where the rostral border is the quadrigeminal plate caudal border is the striae medullares |
|
|
pontine tegmentum - what does it contain
|
Division of pons
contains part of reticular formation (consciousness, etc) and pontine CN nuclei (V) Forms part of floor of 4th ventricle |
|
|
Basilar pons
|
A division of the pons
Bulbous ventral portion contains: cortically dervied axons (corticobulbar, corticospinal, corticopontine) pontine nuclei axonal projections of pontine nuclei to cerebellum |
|
|
CN in pons
|
nuclei for CN V, VI, VII, and part of VIII
|
|
|
Where does CN V emerge
|
from substance of pons (pons and middle cerebellar peduncle)
|
|
|
Where do CN VI, VII, and VIII emerge
|
from pontomedullary junction (inferior pontine sulcus)
|
|
|
medulla oblongata
|
most caudal division of brainstem
derived from rhomboencephalon primary nuclei for autonomic control of respiration, HR, BP, reticular formation connected with the spinal cord |
|
|
Where is the medulla
|
On the dorsal surface (containing the 4th ventricle)
no definitive caudal boundary rostral boundary is striae medullares on ventral surface of brainstem, caudal boundary is pyramidal decussation, while rostral is inferior pontine sulcus |
|
|
Upper medulla
|
open portion of medulla containing the caudal half of the 4th ventricle
on dorsal surface, its caudal boundary is the obex, and the rostral boundary is the striae medullares no definitive caudal boundary on ventral surface, but rostral boundary is inferior pontine sulcus |
|
|
lower medulla
|
closed portion of medulla containing central canal
caudal ventral boundary is pyramidal decussation no definitive rostral ventral boundary' dorsally, no definitive caudal boundary, but rostral boundary is obex |
|
|
where does the corticospinal tract cross
|
midline at the pyramidal decussation
|
|
|
anterior (ventral) median fissure
|
midline furrows between the pyramids extending up from spinal cord
|
|
|
olive (olivary eminence)
|
oval prominence formed by underlying inferior olivary complex, a group of nuclei that send efferents to cerebellum
on medulla |
|
|
preolivary sulci
|
separate olives from pyramids
|
|
|
post-olivary (retro) sulci
|
lie behind olives
|
|
|
posterior (dorsal) median sulcus (fissure)
|
divides the medulla in the mid-sagittal plane
|
|
|
gracile tubercle
|
receives dorsal column info (leg regions, T6 down) from the spinal cord via fasciculis gracilis
in medulla |
|
|
cuneate tubercle
|
receives dorsal column info (areas of upper limb, T6 up)via fasciculis cuneatus
in medulla |
|
|
CN in medulla
|
nuclei for CN IX, X, XI, and XII, with some of VIII
|
|
|
Where do CN IX and X emerge
|
from postolivary sulcus
|
|
|
Where does CN XI emerge
|
partly from postolivary sulcus
|
|
|
where does CN XII emerge
|
from preolivary sulcus
|
|
|
What kind of injury results in more complex deficits
|
Higher level CNS injuries (sensory perception, motor control, programming)
|
|
|
Peripheral nerve injuries
|
Damage to dorsal and ventral roots or a spinal nerve
Deficits are usually mononeuropathy |
|
|
Mononeuropathy
|
Restricted to particular muscles or groups that can be attributed to the functions of a single nerve
Trauma is most common cause |
|
|
What results from damage to dorsal or ventral roots
|
Dorsal - sensory
Ventral - motor Isolated sensory or motor defects with interruption of local reflexes |
|
|
What is usually associated with motor axon injury
|
Weakness (partial paralysis) and muscular atrophy
|
|
|
What is indicative of damage to a peripheral nerve
|
mixed sensory/motor deficits along with localized sympathetic dysfunction (e.g. sweating)
|
|
|
What is a typical cause of isolated sensory or motor deficits
|
Compression of nerve roots as they leave the spinal cord
|
|
|
What are the symptoms of compression of sensory roots
|
Pain or paresthesias
|
|
|
What are the symptoms of compression of motor roots
|
Weakness
|
|
|
What is the term for more widely distributed axon injury
|
Polyneuropathy
|
|
|
What does the stocking or glove deficits indicate
|
Both motor and sensory problems, e.g. diabetes
|
|
|
What kind of axons are affected first in diabetic neuropathy
|
Distal smaller axons are affected first (small unmyelinated pain associated)
followed by large diameter (epicritic touch) later usually feet are affected first |
|
|
Upper motor lesions - where
|
all motor system lesions that involve neurons or tracts that are not directly connected to muscles
|
|
|
Lower motor lesions - where
|
Involve neurons or their axons that directly contact muscle (e.g. alpha, and gamma, peripheral nerveS)
|
|
|
Characteristics of lower motor lesions
|
Flaccid paralysis followed relatively rapidly by atrophy of muscle
Fasciculations or fibrillations of motor units as a result of denervation hypotonia hypotreflexia, areflexia (weakening or absence of tendon reflexes) |
|
|
Poliomyelitis
|
Causes death of lower motor neurons in ventral horn
Varying degree of lower motor neuron deficits that can progress to upper spinal cord and phrenic nucleus and cause death |
|
|
ALS
|
progressive and selective degenration of both upper (corticospinal) and lower (anterior horn) motor neurons
Symptoms are progressive weakness, fasciculations, problems with coordination, then problems with speech, breathing, and swallowing |
|
|
What kind of neurons are brainstem nuclei
|
Lower motor neurons
|
|
|
What is upper motor neuron syndrome primarily the result of
|
Denervation of motor neurons and/or interneurons that contact them
|
|
|
What is a lesion of the pyramidal system an example of
|
Upper motor lesion
|
|
|
Where are upper motor lesions
|
Neurons in cerebral cortex, or anywhere along the axonal course of the tract
Axons caudal to the lesions degenerate and their influence is lost |
|
|
Upper motor neuron syndrome
|
Includes muscles that are initially weak and flaccid followed by spasticity, hypertonia, hyperreflexia, and altered cut. reflexes, including the Babinski sign; clonus or clasp knife response may also be present
|
|
|
Spasticity
|
Spastic weakness
increased resistance to passive movement or manipulation that is velocity dependent |
|
|
Hypertonia
|
increased muscle tone (resting contraction activity)
|
|
|
Hyperreflexia
|
increased responsiveness to sensory reflex
|
|
|
What are symptoms related to increased muscle tone the result of
|
Net loss of overall inhibitory effect on muscle stretch and muscle stretch reflexes
|
|
|
Clonus
|
may be present in patients with hyperactive muscle stretch reflexes
characterized by rapid successive reflex contractions and relaxations of agonists and antagonists mostly observed at the knee and ankle joints |
|
|
Clasp knife response
|
passive stretch of a hypertonic muscle results in a sudden release
believed to be a result of enhanced GTO activation (loss of inhibition by upper motor neurons) but may also involve joint nociceptors |
|
|
Babinski sign
|
Normally tows flex in response to plantar cutaneous stimulation
With upper motor neuron lesions (pyramidal tract) this changes to extension of the great toe and fanning of the other toes Is normal in infants until the upper motor neurons are myelinated May be normal in adults awakening from sleep, in runners after long distance run and in patients with epilepsy |
|
|
Hoffman's sign
|
Upper limb equivalent of Babinski sign
stimulation of middle digit of hand produces reflex flexion of adjacent fingers |
|
|
Is muscle atrophy slower in upper motor neurons or lower
|
It is slower in upper motor neuron lesions and can be attenuated with PT
|
|
|
Isolated pyramidal tract lesions
|
Do not produce all of the disturbances of muscle tone associated with upper motor neuron lesiosn
|
|
|
Symptoms of more isolated corticospinal lesions
|
Positive Babinski sign
Loss of performance of fine skilled voluntary movements, particularly digits Superficial ab reflexes (contraction of abs when scratched) and cremasteric reflexes are absent |
|
|
Which side are symptoms of pyramidal lesions
|
Ipsilateral to a lesion in the spinal cord
Contralateral to a lesion above the medulla |
|
|
How do upper motor neuron lesions present in the brainstem
|
Symptoms may not be as apparent, depending on the extent to which bilateral innervation of the nucleus is present
Usually weakness is greater on contralateral side followed by recovery Some disturbance of reflexes (hyperreflexia) will be present (jaw jerk reflex, for ex) |
|
|
Lesions of what areas are considered upper motor
|
?
|
|
|
Lesions of what areas are considered lower motor
|
?
|
|
|
What can produce the equivalent of an upper motor lesion for visceromotor functions
|
Interruption of axons descending from hypothalamus to brainstem and spinal cord
Preganglionic symp and parasymp neurons lose central control Can result in initial overall reduction of primarily symp activity Clinical signs: low BP, orthostatic hypotension, and bradycardia |
|
|
Autonomic dysreflexia
|
Hyperactivity of autonomic systems
|
|
|
Lesions of hypothalamospinal axons
|
Increased sensitivity and hyperacitivty of autonomic motor neurons
Hypertension, urinary retention, piloerection, profuse sweating and reduction of blood flow to extremities Reflexes can be produced in response to wide variety of stimuli below the level of the lesion |
|
|
Lesions of dorsal columns
|
Epicritic touch, vibration, position sense
measurable and defined deficits |
|
|
Lesions of anterolateral system
|
Pain, temp, protopathic touch
Measurable and defined deficits |
|
|
What will lesions of the long ascending tract disrupt if the DRG entry zone is included
|
Only disrupts local reflexes
|
|
|
What will lesions of medial lemniscal system in brainstem or dorsal columns in spinal cord produce
|
Loss or reduction in 2 pt discrimation, the ability to feel vibration, and the ability to tell the position of a body part in the absence of visual confirmation
|
|
|
Where will deficits be seen from lesions of the dorsal column
|
In the spinal cord - loss is ipsilateral to lesion
Above the medulla - loss is contralateral to lesion |
|
|
Epicritic touch
|
Uusually measured by 2 pt discrimation with dull pts
Can vary markedly over body - less on tongue, more on back |
|
|
How is vibration sense evaluated
|
Using 128 Hz tuning fork on a joint or extremity
|
|
|
Position sense
|
Measured by asking pt to relate whether an extremity has been placed up or down by examiner
Usually use toes to check lower limb function |
|
|
Tabes dorsalis
|
Neurosyphilis
Can produce B/L degeneration of the large diameter dorsal root axons and their cell bodies resulting in degeneration of dorsal columns Results in altered gait, paresthesias, frequent bladder emptying, repressed muscle stretch reflexes |
|
|
What do lesions of the anterolateral system produce
|
Loss of protopathic touch, pain, temp.
If division into ant and lat spinothalamic tracts - pain and temp are more lateral and protopathic touch is more anterior |
|
|
Where is sensory loss in lesion of anterolateral system and why
|
1-2 segments below lesion due to area of dorsal root entry
Contralateral loss of pain and temp at all levels relative to lesion |
|
|
Where do dorsal roots carrying ALS info synapse
|
In dorsal horn, ipsilaterally and the 2ndary neurons send their axons across the midline and ascend in contralateral anterolateral tract
|
|
|
When is protopathic touch more difficult to detect
|
When dorsal columns are intact
|
|
|
How is pain and temp deteced
|
Pain via a pin by asking if it's sharp or dull
temp by using test tubes with warm and cold water |
|
|
syringomelia
|
an ALS lesion
results from cavitation of central canal of spinal cord usually in cervical spine symptoms: B/L loss of pain and temp at or below the level (cloak like sensory loss); as lesion expands to comrpess ventral horns, lower motor neuron symptoms appear |
|
|
Spinocerebellar tract lesions
|
Usually do not occur in isolation and not associated with particular symptoms
with lesions nearer to cerebellum, cerebellar signs may be better distinguished |
|
|
hemiplegia
|
Paralysis of one side of the body (upper limb, one side of trunk, and lowe limb)
AKA Brown-Sequard syndrome |
|
|
Monoplegia
|
paralysis of 1 limb only
|
|
|
Diplegia
|
a paralysis of 2 corresponding limbs (arms or legs)
|
|
|
Paraplegia
|
paralysis of the 2 lower limbs
|
|
|
Pentaplegia
|
quadriplegia with loss of breathing control
|
|
|
Horner syndrome
|
Produces miosis, ptosis, anhidrosis, all due to loss of sympathetic input to the eye
|
|
|
How can a spinal cord lesion produce Horner syndrom
|
Lesion of descending sympathetic input in the spinal cord to the sympathetic chain, ipsilateral to the affected eye
|
|
|
What may cause Brown Sequard syndrome and what are the symptoms
|
symptoms:
loss of all sensation and flaccid weakness in the segments; ipsilateral and below the lesion, there is impairment of proprioception, vibration, 2 pt discrimation, joint and position sensation, spastic weakness and loss of motor control; contralateral and below lesion, impaired pain and temp sensation begins 1-2 segments below lesion |
|
|
Divisions of chronic compression of spinal cord
|
Extradural and intradural
Intradural causes can be divided into intramedullary (within spinal cord) and extramedullary (outside) |
|
|
Causes of extradural spinal injury
|
Disc herniation
Vertebral disease Abscesses |
|
|
Intradural injuries
|
intramedullary causes are usually primary tumors (gliomas)
extramedullary compression is most commonly from meningiomas and nerve fibromas |
|
|
What are the results of chronic compression of the spinal cord
|
Chronic compression usually affects circulation within the spinal cord, both arteries and veins
Compression of arteries can produce slow ischemic injury, vein compression can produce edema With greater pressure, some direct effects on nerve tissue can result |
|
|
Symptoms of chronic compression
|
Pain is one of the earliest signs of chronic compression, usually radiating along the affected distribution of spinal roots; exacerbated by coughing and sneezing and usually worst at night in recumbent position
loss of sensation and motor function depend on source and direction of progression |
|
|
Watershed areas
|
Areas of spinal cord that do not have collateral circulation, particularly in lower thoracic and upper lumbar area
Particularly susceptible to ischemia if blood supply is partially compromised - blockage of single radicular artery can damage spinal cord |
|
|
Damage to artery of adamkiewicz
|
usually on L at L2
damage to it can cause an infarct of lower thoracic and upper lumbar spinal cord |
|
|
Anterior spinal artery syndrome
|
symptoms:
B/L lower motor neuron paralysis in the segments affected (ant horn and n roots), B/L spastic paresis below level of lesion, B/L loss of pain, temp and protopathic touch below the lesion |
|
|
central cord syndrome
|
Typical cause is mechanical injury as spinal cord is compressed ant by vert bodies and post by lig flavum
microvascular reactions to mechanical injury produce a central core of necrosis, while a rim of white matter may be preserved from the larger vessels of the arterial vasocorona |
|
|
Sacral sparing in central cord syndrome - when is it likely to occur
|
sacral functions likely to be spared in corticospinal tract or ALS injuries but not dorsal column injuries
|
|
|
Cauda equina lesions
|
Vraiable
loss of fecal and urinary incontinence sensory and motor deficits along the back of thighs and butt |
|
|
Spinal shock
|
usually with spinal hemisection or complete transection
may be intial period with following symptoms: flaccid paralysis loss of cut. and tendon reflexes compleete anesthesia no sweating B/L Horners in high lesions piloerection retention of urine/feces priapsim if upper level hypotension if uper level may be due to vascular contraction and partial ischemia presence of spinal shock is determined by anal sphincter reflex |
|
|
structure of a peripheral nerve
|
Axons
Myelinating, schwann cells CT vascular supply |
|
|
What does the neuronal cell body reaction to injury include
|
Both neurons in sensory and autonomic ganglia and motor innervation within the spinal cord
|
|
|
What is retrograde neuronal reaction
|
Axon retraction proximal to site of injury, to 1st node of Ranvier
Then cell body that axon comes from undergoes rxn to prepare for axonal regeneration - dispersion of rRNA in Nissl substance (chromatolysis) and movement of nucleus to 1 side of cell |
|
|
When does retrograde reaction occur
|
2-3 days after injury, reaching peak 2 wks after
|
|
|
When is retrograd neuronal rxn most severe
|
when injury is close to cell body
neuron may die |
|
|
WHy is the loss of the axon a severe injury
|
B/c it may contain up to 95% of the cytoplasm of neuron
|
|
|
Anterograde (Wallerian) degeneration
|
Axon distal to injury degenerates
Process involves disruption of axon and phagocytosis of axon by macrophages |
|
|
Schwann cell role in Wallerian degeneration
|
In nerve distal to injury, Schwann cells in distal nerve resorb their myelin and remain in CT tubes, forming bands of bungner
synthesize trophic factors that can act to attract and support the growth of axons |
|
|
Initial axonal regeneration
|
From proximal stump, tip of lesioned axons form sprouts that grow out to find distal stump and enter columns of Schwann cells
Ability of these axons to reach their original destination will depend upon number of variables, including extent of damage and distance to distal stupmp |
|
|
Neuroapraxia
|
Function of axon is disrupted but no physical injury to it
e.g. compression during intoxication |
|
|
axonotmesis
|
axons within nerve are disrupted but CT scaffold (endoneurium, perineurium, epineurium) is intact
Can happen via nerve traction, crush injuries, compression |
|
|
Neurotmesis
|
Axons and CT are disrupted
VIa cutting injuries, other severe trauma |
|
|
Denervation rxns of peripheral tissues
|
Muscle tissue and sensory peripheral tissues lose innervation
Muscles - flaccid paralysis, loss muscle mass, denervation supersensitivity and spread of receptors over surface |
|
|
Muscle atrophy in nerve injuries
|
Due to loss of trophic factors
As it is lost, partially replaced by fibrotic tissue |
|
|
What txs may act like trophic factors
|
PT
Electrical stimulation Injection of substances May delay atrophy |
|
|
Sensory loss from denervation
|
Over area exclusively supplied by nerve, surrounded by zone of partial sensory loss where dermatomes overlap
Light and discrimative touch lost over larger area than pain |
|
|
What may impede sensory recovery
|
Degeneration of Pacinian corpuscles, Merkel endings
Regeneration of sensory axons can be faster than motor |
|
|
Autonomic loss
|
Loss of postgan symp axons in peripheral n resulting in loss of vascular control (skin red and hot at early time, blue and cold later)
sudomotor control is also lost - dry scaly skin denervation of large area can result in bone decalcification from disuse and loss of circulatory control |
|
|
Recovery if axons are not lost (neuropraxia)
|
Faster recovery, unless chronic edema or swelling
|
|
|
Recovery if axons are disrupted (axonotmesis, neurotmesis)
|
Axons must grow back to their targets from site of injury
Axonal regeneration is about 1 inch/month (approx rate of slow axonal transport) |
|
|
What kind of nerve injuries have poor prognosis
|
Neurotmesis
|
|
|
What tends to recover first
|
Sensory
Deep sensation such as pain usually returns first followed by poorly localizeed superficial cut. pain and vasomotor control |
|
|
What recovers 2nd
|
Heat and cold
|
|
|
What recovers last
|
Light touch and discriminative touch, if at all
|
|
|
Tinel's sign
|
Used to test progress of sensory regeneration
Tapping on distal nerve trunk produces tingling sensation in area of cut. sense |
|
|
Peripheral nerve repair
|
In full interruption of peripheral nerve, surgical reapposition of cut ends of divided nerve
2 methods: epineurial nerve suture nerve grafting |
|
|
Epineurial suture
|
Epineurium acts as anchor for sutures
When CT blocks growth of axons, nerve is realigned to fascicles as much as possible, and sutures join nerves |
|
|
Group fascicular repairs
|
Repairing nerves on basis of individual fascicles
mismatching may occur between motor and sensory |
|
|
What may happen if nerves are severely injured
|
Gap between ends of cut nerve, nerve retract as result of CT elasticity
Nerves may form neuroma which can prevent regeneration large gaps, usually use graft |
|
|
Neuroma
|
knot of tissue consisting of combo of axons and CT
|
|
|
Nerve grafting
|
Strip of nerve is harvested from sensory n (e.g. sural) and graft is used to bridge the gap and to try to match fascicular
larger repairs, vascular pedicle may be included |
|
|
Allografts
|
Nerve grafts of fascicles
need immunosuppresion to avoid rejection |
|
|
are CNS axons traveling in tracts accompanied by CT sheaths
|
No
They are myelinated by oligodendrocytes instead of Schwann cells |
|
|
What isolates CNS tissue from peripheral tissue
|
astrocytes and blood brain barrier
|
|
|
Cellular responses to CNS injury
|
Glial barrier and blood brain barrier disrupted
Activation of microglia that phagocytose necrotic tissue disruption of local blood vessels allow peripheral macrophages to invade brain tissue and these gitter cells dissolve necrotic tissue |
|
|
What do astrocytes do in CNS injury
|
Wall off damaged areas from intact tissue by creating dense barrier of astrocytic end feet
|
|
|
Glial scar formation
|
With liquefaction, cystic masses replace tissue and astrocytic barrier is supplemented by collagenous tissue from meninges and blood vessels (glial-pial) scar
|
|
|
What might happen due to factors secreted by macrophages
|
Factors - cytokines, glutamate and others injure tissue (called autolysis)
supress with prednisone, lowering body temp, drug induced coma |
|
|
What is the result of autolytic rxns
|
Can't connect ends of severed spinal cord and joined surfaces will degenerate back, leaving cavity and scar
|
|
|
Retrograde neuronal rxns in CNS neurons
|
Do occur, but do not appear to produce metabolic stimulation associated with axonal regeneration
Slow neuronal atrophy and eventually neuronal loss |
|
|
Abortive regeneration
|
in CNS
axons in areas proximal to lesion site may undergo transient small outgrowth at 2-4 wks after injury, then retract |
|
|
What may happen to other neurons that are directly innervated by injured neuron (CNS)
|
They may also degenerate
ex: visual system, where lesions of optic nerve or retina may induce neuronal loss in lateral geniculate and eventually in visual cortex |
|
|
Factors limiting regeneration of CNS axons
|
Appropriate terrain for axons
Presence of neede trophic and tropic factors presence of glial/pial scar between axons and their targets proteins associated with oligodendrocytes may inhibit axonal growth |
|
|
What does the cranial cavity contain
|
Brain
Meningeal coverings of brain CSF cerebral vascul. CNs |
|
|
What bones make up the anterior cranial fossa
|
Frontal
Ethmoid Sphenoid |
|
|
What does the frontal bone form
|
Bulk of anterior cranial fossa including its anterior wall
|
|
|
What does the orbital plate do
|
Contributes to anterior cranial fossa and is roof of orbit
|
|
|
Cribiform plate of ethmoid bone
|
Centrally in ACF
its crista galli provides attachment for falx cerebri |
|
|
Posterior border of ACF
|
lesser wing of sphenoid
sphenoid limbus |
|
|
What bounds sphenoid limbus
|
Prechiasmic groove posteriorly
|
|
|
Anterior clinoid process
|
At medial end of lesser wing of sphenoid
forms attachment pt for free end of tentorium cerebelli |
|
|
Foramina of ACF
|
foramen cecum
ant. ethmoidal foramen foramina of cribiform plate post. ethmoidal foramen |
|
|
Foramen cecum
|
B/w crista galli and frontal crest
may contain nasal emissary vein connecting nasal cavity with superior sagittal sinus |
|
|
ant ethmoidal foramen
|
midway along frontoethmoidal suture
provides passage for ant ethmoidal nerve (and vessels) which travels forward along crista galli and descending into nasal cavity |
|
|
foramina of cribiform plate
|
passage of olfactory nerve fibers traveling from olfactory mucosa to olfactory bulbs that overlie plate
|
|
|
post ethmoidal foramen
|
posterior end of frontoethmoidal suture
passage for posterior ethmoidal vessels to enter nasal cavity |
|
|
What fossa are frontal lobes associated with
|
ACF
|
|
|
What accomodates olfactory bulbs
|
Cribiform plate of ethmoid bone
|
|
|
3 bones of middle cranial fossa
|
Sphenoid
temporal parietal |
|
|
What does the MCF consist of
|
sella turcica in midline with a deep concavity on each side
|
|
|
what bounds the deep concavities of MCF
|
lesser wings of sphenoid anteriorly
posteriorly by superior borders of petrous temporal bones |
|
|
What forms depressions of MCF
|
greater wing of sphenoid ant
squamous temporal bone and sphenoidal angle of parietal bone laterally petrous temporal bone post |
|
|
boundaries of hypophyseal fossa of sella turcica
|
ant - tuberculum sellae
post - dorsum sellae |
|
|
carotid groove
|
lies on either side of sella turcica and marks path of internal carotid artery through cavernous sinus
|
|
|
Foramina of MCF
|
Optic canal
SO fissure Foramen rotundum FO foramen spinosum foramen lacerum hiatus of greater petrosal n hiatus of lesser petrosal n |
|
|
Optic canal
|
anteriorly at lateral end of chiasmatic groove
transmits optic nerve and ophthalmic artery |
|
|
Superior orbital fissure
|
passage for CNs III, IV, VI, and brs of V1; sympathetic fibers and sup., inf. ophthalmic vv
contains orbital br of middle meningeal a and recurrent br of lacrimal a |
|
|
foramen rotundum
|
behind medial end of SOF in greater wing of sphenoid
contains maxillary div |
|
|
foramen ovale
|
behind and lateral to foramen rotundum in greater wing of sphenoid
contains mandibular div, lesser petrosal n, accessory meningeal a |
|
|
foramen spinosum
|
posterolateral to FO in greater wing of sphenoid
transmits middle meningeal a and v and meningeal br of V3 |
|
|
foramen lacerum
|
opening at posterior end of carotid groove, inferior aspect filled with fibrocart
internal carotid a and its symp plexus travels horizontally across superior part of foramen lacerum from carotid canal to carotid groove ant wall contains opening for pterygoid canal |
|
|
hiatus of greater petrosal n
|
posterolat to int opening of carotid canal on ant surface of petrous temporal bone
greater petrosal n enters MCF via slit called hiatus of facial canal groove for greater petrosal n traveling toward hiatus anteromedially toward foramen lacerum where it is joined by the deep petrosal n (int carotid plexus) to form n of pterygoid canal which enters canal below ant edge of foramen lacerum |
|
|
hiatus of lesser petrosal n
|
lesser petrosal n leaves its hiatus lateral and inf to hiatus of greater petrosal n
|
|
|
trigeminal depression
|
accomodates trigeminal ganglion
behind foramen lacerum near apex of petrous temporal bone |
|
|
tegmen tympani
|
thin osseus plate that serves dual purpose of forming ant surface of petrous temporal bone within cranial cavity and roof of tympanic cavity and mastoid antrum
|
|
|
What cradles the temporal lobes of the brain
|
laterally located concavities of MCF
|
|
|
Where does the diaphragma sellae attach
|
Attaches ant and post clinoid processes of sella turcica
in combo with bony hypophyseal fossa encapsulates pit. gland with central opening for pit. stalk |
|
|
bones of posterior cranial fossa
|
Sphenoid
occipital temporal |
|
|
ant border of PCF
|
superior border of petrous temporal bones and dorsum sellae
|
|
|
posterior border of PCF
|
groove for transverse sinus and midline internal occipital protuberance
|
|
|
internal occipital crest
|
descending from internal occipital protuberance to divide the cerebellar fossa in midline
provides attachment site for falx cerebelli |
|
|
Foramina of PCF
|
jugular foramen
internal acoustic meatus hypoglossal canal foramen magnum |
|
|
jugular foramen
|
at post. end of petro-occipital fissure
contains CNs IX, X (and its meningeal br) and XI; inferior petrosal sinus, int jugular v, meningeal br of occipital a (from ext carotid) |
|
|
internal acoustic meatus - what CNs does it contain
|
above jugular foramen
contains CN VII and VIII as well as labyrinthine a (from AICA or basilar a) |
|
|
hypoglossal canal
|
medial and inf to jugular foramen
contains CN XII, its meningeal br and meningeal br of asc pharyngeal a (from ext carotid) |
|
|
foramen magnum
|
centrally in flood of PCT
passage for accessory nn (CN XI) anterior and post spinal aa and vertebral aa site of jxn b/w spinal cord and medulla oblongata |
|
|
what cradles the cerebellum
|
cerebellar fossa of occipital bone
in PCF |
|
|
pons and medulla in PCF
|
anteriorly in PCF
resting on shelf formed by clivus (basilar part of occipit), post pt of sphenoidal body to which it is attached and dorsum sellae |
|
|
What forms tentorial notch
|
ant concave free edge of tentorium cerebelli
|
|
|
Where is the midbrain positioned and why
|
At opening bw supratentorial and infratentorial compartments of cranial cavity
bc free edge of tentorium encircles midbrain |
|
|
position of rostral medial temporal lobe (uncus)
|
relative to free edge of tentorium
close to midbrain, can herniate midbrain into tentorial notch |
|
|
attachments of tentorium
|
it twists outwardly as it attaches anteriorly with it free edge attachhing to ant clinoid process and its fixed edge attaching to posterior clinoid process
|
|
|
oculomotor nerve exit
|
exits midbrain and travels anteriorly to enter ant edge of tentorium cerebelli
susceptible to injury with increased intracranial pressure as it stretches over this barrier |
|
|
What happens in areas of the brain in which lesioned axons alone are present
|
Wallerian degeneration, at slow rate
accomplished by astrocytes and microglia oligodendrocytes left in place do not proliferate and form bands of bungner like schwann cells do |
|
|
long term degeneration of tissue and tracts
|
microglial cells and astrocytes will phagocytose the degenerating myelin and axons
astrocytes and their processes will replace the degenerating tracts to form a continuous mass of glial processes rather than cavitation detectable in MRI |
|
|
What has inhibited astrocyte and CT scar
|
Antimitotic agents and protein synth inhibitors
could not really help axonal regernation |
|
|
What has been regenerated from transplantation
|
central processes of DRG axons in transplants of peripheral nn
|
|
|
Will CNS axons regenerate in CNS tissue
|
no
|
|
|
ensheathing cells of olfactory epithelium
|
many properties of schwann cells but can also enter CNS tissue
|
|
|
Fetal brain transplant
|
CNS repair
Parkinsons - fetal substantia nigra transplanted into putamen and to some extent, dopaminergic reinnervation |
|
|
What is in the tectum
|
Superior colliculus
Inferior colliculus Crus cerebri Interpeduncular fossa |
|
|
Where does CN III emerge
|
interpeduncular fossa
|
|
|
Where does CN IV emerge
|
Dorsally just below the inferior colliculus
Only one to exit from dorsal aspect of brainstem |
|
|
What CNs is the pons the origin for
|
V, VI, VII, VIII
|
|
|
What outlines the pons
|
Superior and inferior pontine sulci
|
|
|
ventral pons
|
basilar pons
basilar sulcus |
|
|
dorsal pons
|
4th ventricle
striae medullares median fissure |
|
|
What is the basilar sulcus for
|
basilar artery
|
|
|
where is the dorsal pons
|
upper part of rhmoboid fossa
|
|
|
what is the striae medullares
|
axons connecting the pons and cerebellum
|
|
|
Where does CN V emerge
|
from substance of pons
|
|
|
Where do CN VI-VIII emerge
|
from pontomedullary junction
|
|
|
what is the part of the medulla with the ventricle open and closed
|
Upper
Lower |
|
|
What CNs emerge from the midbrain
|
IX, X, XI, XII
|
|
|
What landmarks does the medulla contain
|
Anterior median fissure
pyramids preolivary sulcus, olive, post olivary sulcus posterior median sulcus, median sulcus, obex gracile and cuneate tubercles, gracile and cuneate fasciculi, tuberculum cinereum |
|
|
upper medulla
|
ventricular surface - dorsally
obex is caudal boundary striae medullares is rostral boundary |
|
|
interior pontine sulcus
|
is rostral boundary of ventral surface of upper medulla
|
|
|
lower medulla
|
contains closed extension of spinal canal
pyrimidal is ventral caudal boundary rostral dorsal boundary is obex |
|
|
pyramids of medulla - what kind of axons
|
corticospinal and corticobulbar axons
|
|
|
anterior median fissure of medulla
|
midline furrows extending between the pyramids extending up from the spinal cord
|
|
|
olive (olivary eminence) of medulla
|
oval prominence formed by underlying inferior olivary complex that sends efferents to cerebellum
|
|
|
preolivary sulci
|
separate olive from pyramids
|
|
|
posterior median sulcus of lower medulla
|
divides it in sagittal plane
|
|
|
gracile tubercle and fasciculus gracilis
|
external bumps on lower medulla that receive dorsal column info from T6 down
|
|
|
cuneate tubercle and fasciculus cuneatus
|
receive dorsal column info from T6 up
|
|
|
tuberculum cinereum
|
lateral to cuneate tubercle and fasciculus
|
|
|
Where do CN IX and X emerge
|
From postolivary sulcus
|
|
|
Where does CN XII emerge
|
from preolivary sulcus
|
|
|
Where does CN XI emerge
|
partly from postolivary sulcus
|
|
|
What structures are on the floor of the 4th ventricle
|
Striae medullares
Sulcus limitans facial colliculus hypoglossal trigone vagal trigone |
|
|
Major structures of cerebellum
|
hemispheres
vermis flocculonodular lobe 4th ventricle |
|
|
Where are the tonsils of the cerebellum
|
above the foramen magnum
|
|
|
What are the layers of neocortex (isocortex)
|
Molecular (plexiform layer)
Outer granular layer outer pyramidal layer inner granular layer inenr pyramidal laer multiform layer |
|
|
What is primary motor cortex dominated by
|
Agranular cortex
dominated by pyramidal projection neurons |
|
|
what is primary sensory cortex dominated by
|
granular cortex
dominated by smaller cells, most notably stellate cells |
|
|
Pyramidal neurons
|
in all layers except layer I
prominent in layers II, III, V large apical dendrite - extends toward molecular layer basal dendrites - projecting horizontally major output pathway of cerebral cortex giant pyramidal neurons |
|
|
Where are giant pyramidal neurons of Betz
|
Only in motor cortex - layer V
|
|
|
Intrinsic neurons
|
stellate (aspiny and spiny)
Chandelier Basket Cells of Martinotti |
|
|
Stellate neurons - where are they most numerous, what kind of projections do they receive
|
|
|
|
Chandelier cells - what layer
|
in layer III
dendrites in layer IV |
|
|
Basket cells - what layers
|
Layer III and V
dendrites in all layers |
|
|
Cells of Martinotti
|
Found in deeper layers
multipolar neurons with short branching dendrites |
|
|
Intrahemispheric (association fibers)
|
Long association - connect lobes together more distant regions)
short assocation - connect gyri together |
|
|
interhemispheric (callosal fibers)
|
connect L and R hemispheres (corpus callosum) and temporal poles (anterior commissure)
|
|
|
Local intrinsic axon
|
connect different layers together
|
|
|
Corticofugal
|
go to subcortical areas, brainstem, and spinal cord
what types? |
|
|
corticopetal
|
from the thalamus (thalamocortical) to layer IV (some to layers III and VI)
|
|
|
What are the structure and function of the cerebral cortex
|
heterogenous, although it appears as homogenous sheet
|
|
|
What are structural differences of cerebra cortex base don
|
cortical thickness
width of indivudal layers number of cells per layer |
|
|
What do Brodmanns areas describe
|
Functional areas of cortex
|
|
|
Area 4
|
primary cortex
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Area 6
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premotor cortex and supplementary motor area
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areas 45, 44
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broca's area on left (pars triangularis and opercularis of interior frontal gyrus)
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areas 3, 1, 2
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primary somatosensory cortex
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areas 5, 7
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somatosensory association areas
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area 17
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primary visual cortex
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areas 18, 19
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visual association cortex
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areas 41, 42
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primary auditory cortex
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area 22
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auditory association cortex (L posterior - Wernicke's area)
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Major functional components of frontal lobes
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Primary motor cortex
Supplemental motor areas Frontal eye fields Prefrontal cortex |
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What separates the frontal lobes from the parietal lobes
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central sulcus
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What separates the frontal lobes from the temporal lobe
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proximal part of lateral fissure
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What are the primary gyri of the frontal lobe
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precentral gyrus (primary motor corteX)
superior, middle, and inferior frontal gyri separated by precentral sulcus and superior and inferior frontal sulci |
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What does the precentral gyrus continue within the longitudinal fissure as
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Anterior paracentral gyrus
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What does the superior frontal gyrus extend on the medial surface as
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Down to cingulate sulcus
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What is the paracentral lobule
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a medial extension of both the pre and post central gyri
contains both primary motor (anterior) and primary sensory (posterior) functional areas |
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What is the precentral gyrus
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Brodmann area 4
primary motor cortex major motor output to spinal cord and brainstem somatotopically organized - areas that represent legs are located in anterior paracentral gyrus trunk, hand, head, and tongue are represented more inferiorly and laterally with the tongue represented near the lateral fissure |
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Supplementary motor and premotor areas
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In front of precentral gyrus
related to planning of motor activities (Area 6) these areas communicate with area 4 and subcortical structures (basal ganglia, cerebellum, etc) in the planning of movements |
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frontal eye fields - what area
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anterior to premotor cortex
area 8 facilitate the cortical (conscious) control of eye movements through connections to eye movement centers in the brainstem |
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parts of inferior frontal gyrus
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pars opercularis near lateral fissure
pars trangularis pars orbitalis |
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pars trangularis and pars opercularis
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Broca's areas 45, 44, motor area for speech in the dominant (usually L) hemisphere
connect to brainstem nuclei for cranial nerves that control the motor output for speech |
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Prefrontal cortex
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much of it is classified as mutlimodal associational with diverse cognitive functions including jusgement, foresight, a sense of purpose, responsibility and social propriety
contains 25% of entire cortex of the human brain - primarily Brodmann areas 9-12 |
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What do the prefrontal areas extend into ventrally
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Orbitofrontal gyri
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Where are the olfactory bulb and tract
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In olfactory sulcus, forming a medial boundary of the orbitofrontal gyri
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Grus rectus
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most medially, next to longitudinal fissure
essentially an extension of the medial aspect of the superior frontal gyrus |
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Parietal lobes
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sensory and multimodal function
Contains: primary somatosensory cortex sensory association areas |
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Primary somatosensory cortex
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postcentral gyrus
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sensory association areas of parietal lobes
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functions include understanding spoken and written language (usually L hemisphere)
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Lateral boundaries of parietal lobes
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posterior to central sulcus
anterior to extension of parieto-occipital sulcus to preoccipital notch |
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parietal lobe boundaries from temporal lobe
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above lateral fissure and a line between approx the middle of the lateral fissure and the extension of the parieto occipital sulcus
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what do the parietal lobes contain medially
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posterior part of paracentral lobule
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what separates the parietal lobe from the occipital lobe
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parieto-occipital sulcus
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what is the precuneous
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between boundaries of parietal lobes
bordered inferiorly by an indistinct boundary with the cingulate gyrus |
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primary components of parietal obes
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primary somatosensory cortex (postcentral gyrus)
superior parietal lobule inferior parietal lobule (supramarginal gyrus, angular gyrus) |
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What separates the superior and inferior parrietal lobules
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Intraparietal sulcus
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Where is the postcentral gyrus
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behind the central sulcus and anterior to postcentral sulcus
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What does the postcentral gyrus contain
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primary somatosensory cortex (brodmann areas 3,1,2) on lateral surface of hemisphere
posterrior paracentral lobule on the medial surface of the hemisphere |
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Organization of postcentral gyrus
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somatotopically organized similarly to motor cortex
sensory areas from the genitals, foot, and leg are on the medial hemispere in the posterior paracentral gyrus tongue is most laterally |
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What do neurons in the postcentral gyrus respond to
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modality specific stimuli of disciminative touch, vibration, position, pain, and temperature
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secondary somatosensory cortex (SII)
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on medial surface of the parietal operculum
contains additional sensory somatotopic map, although somewhat more crude than SI |
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SI
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?
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What do SII areas project to
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Insular cortex, which distributes to limbic areas, presumably for the memory of tactile stimuli
viscerosensory input also projects to adjacent areas in this region |
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Insula
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Contains long and short insular gyri surrounded by the border of lateral fissure (circular sulcus)
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What might the anteiror insula do
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coordinate articulatory movements necessary for speech
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What does the superior parietal lobe so
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Brodmann areas 5 and 7
integrates somatosensory input from multiple modalities that are used in motor planning (kinesthetic sense, hand eye coordination) project to supplementary motor areas in frontal lobe |
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inferior parietal lobule
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contains the angular gyrus (Area 39) and supramaringal gyrus (Area 40)
functions differ with hemisphere involved - in dominant hemispehere, the angular gyrus is a center for comprehension of written language |
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Suprmarginal gyrus
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Areas of it and posterior superior temporal gyrus (wernicke's area, brodmann area 22) is the areas for comprehension of spoken language
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What does the infeioer parietal lobule do in the nondominatn hemisphere
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modulates attention to stimuli both on the body and in the visual field
lesions to this area are associated with hemineglect syndrome - failure to recognize the L side of the body as self |
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What do the occipital lobes contain
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Funciton: visual
primary visual cortex and visual association (extrastriate) cortex |
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What separates the parietal and occiptial lobes
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parieto occipital sulcus
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What does the calcarine sulcus do
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divides the medial occipital lobe into the cuneus above and lingual gyrus below
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Extrastriate cortex (areas 18,19)
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Involved in processing of visual data leading to perception of motion, depth, color, position of object
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primary visual cortex
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Area 17
on medial ide of occipital lobe on either side of the calcarine sulcus |
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What represents the retinal surface
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topographic (retinotopic) fashion of org around the calcarine sulcus
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temporal lobes
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integrative sensory, some memory, auditory and olfactory functions
contrains primary auditory cortex and nearby wernicke's area that coordinates the understanding of spoken language also contains limbic areas, including hippocampus |
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What is the temporal lobe composed of on its lateral surface
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superior, middle and inferor temporal gyri, separated by superior and inferior temporal sulci
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What may the inferior temporal gyrus become ventrally if folded over to the inferior surface
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latera occipitotemporal gyrus (fusiform gyrus)
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medial occipitotemporal gyrus
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may be present and if so is separated from the lateral by the occipitotemporal sulcus
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What are the later occipitotemporal and medial occipitotemporal gyrus involved in
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recognition of objects and faces
along with adjacent areas of occipital lobe |
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what does the superior surface of the the temporal lobe contain within the lateral fissure
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transverse temporal gyri (of heschl, areas 41, 42)
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Primary auditory cortex
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Audition, receiving info from both ears
with surrounding association cortex, is involved in processing of assocation and recognition of sounds |
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Limbic lobe functions
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primary processor of memory
emotion behavior, integration of homeostatic responses, motivation, and sexual behavior |
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What does the limbic lobe contain
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major divisions:
subcallosal area cingulate gyrus parrahippocampal gyrus uncus Contains: primary olfactory cortex multimodal assocation cortex |
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Cingulate sulcus of limbic lobe
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separates the limbic lobe from anterior and dorsal structures
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callosal sulcus of limibic lobe
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separates corpus callosum from limbic lobe
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What does the cingulate gyrus continue as ventrally
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parahippocampal gyrus
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what does the collateral sulcus do
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separates the parahippocampal gyrus from the occipitotemporal gyri
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What do the anterior regions of the parahippocampal gyrus contain
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primary olfactory cortex (AKA entorhinal, prifirom)
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What are the hippocampus and cingulate gyrus necessary for
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Incorporaiton of short term to long term memory
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What do the hippocampal formation and adjacent areas of parahippocampal gyrus have interconnections with
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cingulate gyrus
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