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268 Cards in this Set
- Front
- Back
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Forebrain
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Telencephalon + Diencephalon
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Mesencephalon
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Midbrain
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Metencephalon
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Pons + cerebellum
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Myelencephalon
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Medulla
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Rhombencephalon
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Metecephalon + Myelencephalon (Pons, Cerebellum, Medulla)
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Brainstem
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midbrain, pons, medulla
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Brain
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Brainstem, cerebellum, forebrain
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White matter
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myelinated axons (cortex inwards, spinal cord outwards)
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Grey matter
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cell bodies (cortex outwards, spinal cord inwards)
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Association (White matter)
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Mediates communication between areas WITHIN a hemisphere
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Commissural (white matter)
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Mediates communication between areas BETWEEN hemispheres
Major Commissural = Corpus Collosum |
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Projection (white matter)
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Mediates communication between cortical and subcortical sites
Major Projection - Internal capsule |
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Lateral Geniculate Nucleus
Location? Function? |
Lateral Geniculate Nucleus
Location: Thalamus (Diencephalon) Function: relay station between retina and primary visual cortex |
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Suprachiasmatic nucleus
Location? Function? |
Suprachiasmatic nucleus
Location: hypothalamus (Diencephalon) Function: trigger circadian clock |
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Pretectal Nucleus
Location? Function? |
Pretectal Nucleus
Location: Midbrain (Mesencephalon) Function: afferent limb of pupillary light reflex |
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Superior Colliculus
Location? Function? |
Superior Colliculus
Location: Midbrain (Mesencephalon) Function: Contribute to Eye Movements |
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Magnocellular
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- Dorsal (parietal pathway)
- Depth and Motion (location & movement) - 1st 2 layers - detects fast moving stimulus |
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Parvocellular
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- Ventral (temporal pathway)
- Form & Color (Color vision & acuity) - projects deeper into the primary visual cortex -layers 3-6 |
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What portion of the visual field is lost at lesion 1?
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Monocular Blindness
Lesion: Optic Nerve total blindness in 1 eye |
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What portion of the visual field is lost at lesion 2?
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Lesion: Optic Chiasm
Bitemporal hemianopia Cut Nasal Retina Input. |
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What would be lost on the visual field in lesion 4?
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Superior Homonymous Quandrantanopia
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What part of the visual field would be lost at lesion 7?
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Macular Sparing
Fovea Spared. notched hemifield |
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Where part of the visual field is lost in lesion 3?
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Homonymous hemianopia
Lesion in Optic tract or Posterior cerebral artery dysfunction |
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Inferior colliculus
Location? Function? |
Inferior colliculus
Location: Midbrain (Mesencephalon) Function: involved in the localization of sound |
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Type of receptor on ON bipolar cells
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E (Glutamate [metabotropic receptor])
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Superior Visual Field
is temporal/parietal radiation? is above/below calcarine sulcus? |
Superior Visual Field
is temporal radiation is below calcarine sulcus |
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Inferior Visual Field
is temporal/parietal radiation? is above/below calcarine sulcus? |
Inferior Visual Field
parietal radiation above calcarine sulcus |
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Ocular Dominance Columns
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Alternating by which eye input comes from [ipsilateral & contralateral]
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Orientation Columns
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Light Orientation (horizontal, vertical)
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Dark Current
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- photoreceptors are depolarized and releasing glutamate in the dark.
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What is the neurotransmitter for photoreceptors?
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glutamate
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Protanopia
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Red cone color blindness
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Deuteranopia
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Green Cone Color Blindness
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What is the rarest type of color blindness?
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Blue
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What kind of receptor is a ON Bipolar cell?
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Glutamate (metabotropic)
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What kind of receptor is a OFF Bipolar cell?
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Ionotropic
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Epidural Hematoma
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- Hemorrhage of ARTERY (usually Middle Meningeal)
- Biconvex shape - Lucid for a while and then die suddenly |
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Subdural Hematoma
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- Hemorrhage of bridging VEIN
- Crescent Shaped - Venous System - lower pressure than arterial. = takes approx 4-6 weeks for symptoms. - Vague Symptoms. - Chronic rather than acute - Trauma or Elderly |
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emx
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homeobox gene
- deficiency = schizencephaly (split cortex) |
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otx
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homeobox gene
- deficiency = epilepsy |
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hox genes
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direct fate of cells within a segement
- ie. master gene in drosophilia |
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BMP (Bone morphogenic Protein)
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- induction of neural plate
- Early - suppress neural differentiation and promotes epidermal tissue - Later - is blocked so that ectoderm can form neural plate |
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PMP22
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mutation of PMP22 = Charcot Marie Tooth Syndrome
-PMP22 =produced in schwann cells for myelination |
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Sonic Hedgehog
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- NOT a homeobox gene
- influences development of serotonergic neurons - hindbrain dopaminergic neurons - posterior midbrain oculomotor neurons - anterior midbrain - secreted by notochord - acts on floor plate to induce netrin formation is a protein |
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Hensen's Node
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Anterior-Posterior Hox gene expression
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Radial Glia persist in adults as
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Muller cells (Retina)
Bergman Glia (cerebellum) |
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astrotactin
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proteins that mediate neuronal migration
if blocked = no cell migration Receptor = Integrin |
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Reeler
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large extracellular matrix glycoprotein
If Mutated - neurons fail to migrate past each other - positions inverted - Expressed in Cajal-Retzius cells - tell cells to 'get off' the glial monorail |
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Kallman's Syndrome
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- no sense of smell
- no sexual maturation |
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PNS neural crest cells migrate along pathways that
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LACK
1) axons tracts 2) organized glial structure |
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laminin
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- made by Schwann cells after injury
- promotes neural outgrowth Antibody against laminin = block neurite extension and outgrowth |
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What activates transcription of Hox genes?
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Retionic Acid
- creates a Anterior- posterior gradient |
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What kind of neurons can move without radial glial cells?
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neurons with Gonadotropin-releasing hormone
failure of GnRH migration = Kallman Syndrome = ↓ olfactory and sterile |
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Axon growth is influenced by:
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Diffusible Molecules and Proteins from Extracellular Matrix
1. Pioneer Axon - leads the way. has extensive filopodia 2. Netrin - released by floor plate. causes axons to cross anterior commissure 3. Laminin - secreted by Schwann cells after accident; promotes neural outgrowth 4. Growth cone - enlarged axon extension. Receptors are on axon surface. cones may release enzymes to clear pathway and change substrate |
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Growth cone
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enlarged axon extension. Receptors are on axon surface. cones may release enzymes to clear pathway and change substrate
- in axonal growth |
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Netrin
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released by floor plate. causes axons to cross anterior commissure
- in axonal growth |
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Pioneer Axon
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leads the way. has extensive filopodia
- in axonal growth |
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Leukemia Inhibitory Factor
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- peptide secreted to change crest cells
- induces differentiation in immune system |
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agrin
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released by nerve.
makes receptors on NMJ concentrate on end plate |
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semaphorin
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short range inhibitory signal
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Trembler mouse
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- myelin formed to fail
- genetic defect in Schwann cells Sciatic nerve tansplant experiment |
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Charcot Marie Tooth Diease
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PMP22 mutation
gly to asp (amino acid substitution - peripheral myelin fails to form properly |
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NCAM
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Neural Cell Adhesion Molecule
- binds to itself and causes axons to stick to one another - bound axons are wrapped by shared glia -Fab part of antibody can disrupt bundling of growing axons |
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Nerve Growth Factor
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- from snake venom and salivary glands
- causes growth of neurites - required for sensory cell outgrowth - antiNGF = smaller Dorsal Root Ganglion - affects Sympathetic NS but not Parasympathetic - each cell types CRITICAL PERIOD = survival depends on supply of NGF - Transported into Soma, regulates synthesis of NORE via 1 tyrosine hydroxlase, dopamine b-hydroxylase |
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Brain derived neurotropic factor (BDNF)
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- protein in CNS that promotes survival of DRG
- very similar to NGF - can rescue cells from neuronal death if administered |
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Neurotrophin
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- Family of growth factors, including BDNF and NGF
- dimers with basic regions held together by cysteine residues In Early development, before sensory neurons innervate target, Neurotrophin needed for: - neural crest cells -sensory neurons -Dorsal Root Ganglion -Trigeminal Ganglia |
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p75
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low affinity, fast NGF receptor
found on neurons and non-neuronal cells |
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p140prototrk (trk)
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high affinity receptor
- found only in neurons - mediate cell survival and neurite outgrowth - intracellular domain has Tyrosine Kinase - activates Intracellular Signalling Pathways: 1. PLC 2. Phosphatidylinositol 3 Kinase 3. MAP Kinase |
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trkA
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High affinity receptor for NGF
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trkB
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High affinity receptor for BDNT and NT-4/5
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trkC
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High affinity receptor fro NT-3
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BDNF influences
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retinal ganglion cell branching and remodeling
dendritic growth of cortical neurons formation of ocular dominance columns within developing visual cortex |
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Ephrin
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- responsible for repulsive interactions during cell signaling
- cell migration, axon pathfinding and cell intermingling - part of receptor tyrosine kinases ephrin-A2 and ephrin A-5 are in tectum |
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Thalidomide
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- reduce limbs to flipper like appendages
1. primary effect = neurons 2. secondary effect = bone growth |
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Albinism
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frequent miswiring of retinogeniculate connections
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Microglia
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macrophage of CNS
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Astrocytes
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- homeostatis at synapse
- regulates chemicals - recycles Neurotransmitter - building block of BBB - Release antioxidants to protect neurons - uptake of excess Neurotransmitters via transporters - secretes cholesterol for neural development Signals via IP3/Ca2+ |
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oligodendrocytes
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coats CNS with myelin
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Ependymal Cells
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Secretes CSF
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Radial Glia
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- Scaffold that developing neurons climb on
Persists in the adult as: - Muller cells - retina - bidirectional communication with neurons - Bergmann Glia - cerebellum - regulate synaptic plasticity |
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Bergmann Glia
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Radial Glial cells in the cerebellum - regulate synaptic plasticity
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Muller cells
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Radial glia in retina - bidirectional communication with neurons
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Schwann Cells
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myelinate PNS axons
phagocytic activity |
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Satelitte cells
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regulates external chemical environment.
- surround sensory, sympathetic, parasympathetic |
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Tanycytes
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ependymal cells in 3rd ventricle. Bipolar cells that link CSF to neuroendrocrine events
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Enteric Glial
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analagous to CNS astrocyte but in Enteric Nervous system
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Tripartite Synapse
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close proximity of pre, post and glial cell
- both neuron and glia can release neurotropic factors - Glial-cell derived neurotropic factor (GDNF) - Brain derived Growth Factor (BDNF) - Neurotropin-3 |
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Perivascular Astrocytes
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astrocytes that maintain blood flow and osmotic balance in brain
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Tanycyte
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bipolar cells that link CSF to neuroendocrine events.
- radial glial that differentiate with astrocyte like properties |
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Schwann cells
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in PNS
- myelinate AND phagocytic activity |
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glial scar
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- During trauma or ischemia
- astrocyte form scar to isolate neurons from each other - presence of glial scar = limits the possibility of axonal regeneration in CNS |
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Astrocytes store _____________
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glycogen
- can be converted to lactate and be used as an alternate supply of ATP |
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Astrocytes have what kind of receptors:
1. Ionotropic 2. Metabotropic |
both
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Spatial Buffering/Potassium Siphoning
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- astrocytes take in K+ from extracellular fluid and redistributes to its neighbors (via gap junction)
- K+ from action potentails |
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Amyotrophic lateral sclerosis
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loss of brain and spinal cord motor neurons
- mutation in Superoxide Dismutase and astrocytes |
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Gliosis
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hyperplasia and hypertrophy of astrocytes in response to injury in CNS
= Glial Scar |
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Glial Fibrillary Acidic Protein (GFAP)
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- encodes filament protein for mature astrocytes
Disease = Alexander Disease |
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Anterograde Degeneration
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degeneration of the neuron postsynaptic to the damaged neuron
- Wallerian degeneration - after the axon has been cut |
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Retrograde Degeneration
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degeneration of the neuron, before the lesion
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Chromatolysis
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when lesion next to cell body
- swelling and movement of cell organelles away from the cell body |
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Multipolar neurons are
Efferent/Afferent |
Efferent
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Pseudounipolar neurons are:
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Afferent
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Bipolar cells are:
Motor/Sensory |
Sensory
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synaptic potentials
1. do not spread with decrement 2. spread with decrement |
spread with decrement
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action potentials
1. do not spread with decrement 2. spread with decrement |
do not spread with decrement
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Collateral Axon branch
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branch of main axon that feeds back onto soma providing modulation of cell firing
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Nissl body
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histological sign of rough ER; site of protein synthesis
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What is the main determinant of shape of the neuron?
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cytoskeleton
ie. microtubules, neurofilaments, microfilaments" |
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Multiple Sclerosis
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- degeneration of myelin in CNS
- autoimmune - reduced axonal velocity - CN II is only cranial nerve demyelinated in MS as well as problems with hearing and balance (caused in brainstem, not CN) |
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Guillain-Barr Syndrome
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-degeneration of myelin in PNS
- affects both myelin and axons themselves |
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Neurofilament
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-most common filament in neurons
-highly stable -undergo little turnover - Scaffolding for cytoskeleton of neuron |
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Microtubule
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-13 protofilaments forming a tubule (α/β)
- associated with dynein and kinesin - damage to microtubule = cell death - transport between nerve cell and soma" |
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Remak Fiber
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unmyelinating Schwann cells that envelope small axons to regulate [K+]
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Choroid Plexus
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Ependymal cells - Group 1
Secretory, grouped by TIGHT JUNCTIONS |
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Ventricles & Central Canal
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Ependymal cells - group 2
- Assists in CNS CSF circulation joined by GAP JUNCTIONS - solutes pass paracellularly |
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Resting potential of neuron
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-65
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Resting potential of skeletal muscle
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-90
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Resting membrane potential of photoreceptor
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-40
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In neurons, membrane potentials are affected by which ion?
K+ Ca2+ Na+ H+ |
K+
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The main difference between neurons and glia is:
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The main difference between neurons and glia is how they transfer info
Neurons: Action Potentials Glial cells - Intra/Inter-cellular Ca2+ signalling |
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Dynein
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"- fast RETROGRADE transport
- nerve ending back to soma - motor protein for movement in cilia and flagella - inactivated in soma and carried back to nerve ending -ATPase - carries lysozymes, enzymes and recycled vesicle membranes" |
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Kinesin
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fast ANTEROGRADE transport
- soma to nerve ending - ATPase - allows attachment of large structures (vesicles, mitochondra) - Kinesin is inactivated at nerve ending and carried back via retrograde" |
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What excites astrocytes?
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[Ca2+] not voltage
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Which is faster: electrical signaling or axonal transport?
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Electrical Signaling
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Channelopathies
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dysfunctional ion channels
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Cytotoxic Edema
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edema following ischemia (interrupted blood supply)
- affects Grey more than white - edema b/c failure to supply Na+/K+ pump with ATP = ions dissipate - Increased Intracellular water and Na+ in edema fluid - Clinical Disorders: Hypoxia, Water intoxication, Ischemia |
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Vasogenic Edema
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blood vessels become permeable and fluid accumulates in extracellular space
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The Membrane Potential (Vm) depends on
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number of open channels for ions
conductances of the open ion channels equilibrium potentials for those ions |
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What happens with lethal injection?
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- Lethal Injection = KCl
-raise extracellular K+ - depolarizes excitable cells - fails to generate another action potential b/c voltage gated Na+ channels are inactivated |
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Efferent neurons and Interneurons
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have membrane proteins that are chemoreceptors for NT
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Afferent
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membrane receptors responding to a specific type of stimulus
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Golgi Tendon Organ
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Mechanoreceptor in muscle
- measure TENSION - muscle mechanoreceptor measures stretch |
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Mechanoreceptors in muscle
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measure STRETCH
- golgi tendon organs measure TENSION |
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anosmia
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loss of olfactory sensation
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spasticity
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increase of muscle tone.
hyperexcitability of stretch reflex with decrease in reflex threshold |
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Enkephalin
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regulates nociception
made in hindbrain opoid pepetide |
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Biogenic amines
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catecholamines, indoleamine, imidazoleamine, purine
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Neuropeptide Y
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- in CNS and PNS
- CNS - cortical excitability, circadian rhythm, stress response, pain processing, emotion, food response - PNS - cardiovascular function, blood pressure, vasoconstriction |
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Vasopressin
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from hypothalamus
-stored in posterior pituitary Vasopressin = ADH |
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Dynorphin
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regulates nociception
opoid Leu-Enkephalin |
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Nitric Oxide
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not stored in vesicles
made on demand release not Ca2+ dependent doesn't interact with postsynaptic cleft |
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Synapsin
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Gets phosphorylated. release vesicles from cytoskeleton
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Rab Protein
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transports vesicle to site of exocytosis
(moves vesicle to active site) |
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Synaptobrevin
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Docking of vesicle of nerve membrane.
(partially docked) - Binds to syntaxin. |
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Synptotagmin
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Docking of vesicle of nerve membrane.
(fully docked) - Binds to neurexin. |
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Synaptotophyin
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forms fusion of vesicular and nerve membrane.
Fully docked to nerve membrane |
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small clear vesicles
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- AcH, serotonin, glycine
- recycled locally (at the synapse) - low nerve stimulation (10Hz) causes a rise in Ca2+ near active zone and causes exocytosis |
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dense core vesicles
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- peptides (NE, Serotonin)
- high nerve stimulation rate (100Hz) cause a rise in Ca2+ near active zone = exocytosis |
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Botulinum Toxin
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- blocks Ach release
- blocks synaptobrevin (Ach can't dock) - diplopia, dysphasia, dysphagia dry mouth = botox injection |
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Tetanus Toxin
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blocks glycine release
- blocks synaptobrevin (glycine can;t dock) - |
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α-Latrotoxin
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massive release of AcH = depletes all of Ach
then nothing. flaccid paralysis |
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4-aminopyridine (4-AP)
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- blocks K+ channels and increases duration that Ca2+ release = more AcH
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neomycine/streptomycin
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inhibit Ach exocytosis at high concentration = blocks nACHr
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Monoamine Oxidase breaks down:
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norepinephrine, epinephrine, dopamine, serotonin
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Catechol O-methyltransferase (COMT) degrades:
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norepinephrine, epinephrine, dopamine,
Does not degrade serotonin (unlike MAO) |
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M2 Receptor
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Ach receptor
In Heart ↓ cGAMP inhibits pacemaker cells coupled to K+ and Ca2+ Channels = closure of Ca2+ channels Inhibitory - slower spontaneous depolarization and slower HR |
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M3 receptor
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Ach Receptors
- stimulates exocrine glands and eccrine glands - also stimulates smooth muscle ↑ PLC = ↑ IP3 and DAG ↑ Ca2+ release |
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Excitatory M receptors
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M1, M3, M5
via phospholipase M1, M3 = brain M3 - secretory and smooth muscle |
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Inhibitory M receptors
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M2, M4
M2 = heart |
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Dopamine
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mostly in CNS. not much in PNS
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Norepinephrine
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activates adrenoceptors of smooth muscle, glands, cardiac
(Sympathetic) |
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Ephinephrine
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released by chromaffin cells
enters circulation ultimate activates adrenoceptors |
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Isoprenaline
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synthetic catecholamine
similar structure to ephinephrine |
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D1 and D5 Dopamine Receptors
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↑ cAMP production
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D2 (D3, D4) Dopamine receptors
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↓ cAMP production
↑ D2 = psychosis - give D2 anatagonist ↓D2 = parkinsons. - give D2 agonist |
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Glycine
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inhibitory in the spinal cord
- ionotropic - permeable to Cl- - 3 glycines to bind - resembles nACHr |
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GABA
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- inhibitory in the brain and brainstem
- 2 GABA to bind - mediates FAST IPSP -metabotropic - indirect K+ channels open thru 2nd messenger - mediate slow inhibition of postsynpatic neuron -anti-anxiety drugs inhibits Amygdala (responsible for fear/anxiety) |
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Glutamate
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has both metabotropic and ionotropic
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AMPA
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allows Na+ to enter
Ionotropic |
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NMDA
|
allows Ca2+ in
(blocked by Mg2+) - when v. large depolarization, many EPSP = membrane induces Mg2+ to leave Unblocked NMDA = Ca2+ enters = - long lasting physiological changes in cell - activated during intense synpatic activity |
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SSRI
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for clinical depression
- allows more available SEROTONIN in CNS - slows down 5-HT receptor = ↓ reuptake |
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Pilocarpine
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naturally occurring alkaloid
mimics AcH - agonist at all muscarinic receptors - used for glaucoma (faciliates fluid drainage from eye via canal of schlem) |
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Beta blockers
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antagonist of B1 receptors
treat hypertension - antagonize vasoconstriction action of Norepinephrine |
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how does the composition of CSF compare to serum (in terms of Protein, K+, Na+, Ca2+ and Cl-)?
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CSF
- less protein - less cations (K+, Na+, Ca2+) - more Cl- - produced by direct secretion |
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Presence of RBC and high [protein] in CSF is a sign of
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Subarachnoid hemmorhage
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Glucose crosses the BBB via
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GLUT1 transporter.
facilitated diffusion |
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L-dopa crosses the BBB via
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facilitate diffusion
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Glycine crosses BBB via
(From brain to blood) |
Na+ dependent secondary active transport
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CSF is absorbed by
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arachnoid villi in the superior sagittal sinus
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Presence of ↑[cell] and ↓ [protein] in CSF is a sign of
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Bacterial meningitis
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Presence of ↑[cell] and normal [protein] in CSF is a sign of
|
Viral Meningitis or brain tumor
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Papilloma
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tumor in CSF
- communicating hydrocephalus - all ventricles enlarged |
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Normal Pressure hydrocephalus
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- no rise in intracranial pressure
- reduction of brain volume - usually in elderly only - enlarged ventricles, sulci and fissures with flattening cortical gyri against skull |
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ependymal cells transfer water and nutrients via
paracellular/transcellular |
paracellular
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Dandy Walker Syndrome
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Foramina of Luschka and Magendie fail to develop
- Dilatation of all 4 ventricles - congenital |
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Congenital Hydrocephalus
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Usually due to blockage of cerebral aqueduct
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How is Intracranial Pressure measured?
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Spinal tap (L4/L5 or L3/L4)
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1A afferents
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- excite motor neurons & interneurons
in spinal cord - release glutamate |
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EPSP
metabotropic or ionotropic |
Ionotropic - CATION receptors
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IPSP is invoked by which neurotransmitter?
|
Glycine or GABA
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Renshaw Cell
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Interneuron
signals from a motor neuron running collaterally back via the ventral horn into the spinal cord, there were interneuron’s firing with a high frequency, resulting in inhibition |
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Transient Ischemic Attack
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acute loss of cerebral functions for ~24 hours
-caused by temporary blockage of cerebral circulation -full recovery likely. |
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Reversible ischemic attack
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neurological deficit is acute loss of cerebral or monocular function
-symptoms last longer than 24 hours; -recovery is still likely. |
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Striae medullares
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strands of the vestibulocochlear nerve (CN VIII) which wind around inferior peduncle, disappearing into median sulcus.
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Gracile tubercle
|
function is for fine touch and proprioception.
corresponds to neurons of gracile nucleus which is one of dorsal column nuclei |
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Cuneate tubercle
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Cuneate nucleus is part of dorsal column-medial lemniscus system, which carries fine touch and proprioception information to thalamus and cerebellum.
- located inferior to gracile tubercle. |
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Blood supply of the Pons
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branches of the Basilar artery
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locked-in syndrome
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- not enough blood supply (i.e. due to stroke) to ventral portion of pons
-horizontal eye movement and facial expression (along with all other voluntary muscle actions) will be non-functional |
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Ataxia
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problem in performing smooth, coordinated muscle movements, generally resulting in a wide gait.
-Ataxia is caused by a problem with cerebellum or cerebellar peduncles. |
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Erlanger & Gasser
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- used for spinal nerves, and can be both motor and sensory.
- A, B,C,D - A = thickest and highest conduction velocity |
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Lloyd classification
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- used for afferent nerves in skeletal muscle
- I-IV I = thickest and highest conduction velocity IV = thinnest. slowest |
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Membrane Conductance (equation)
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membrane conductance = total # of open channels x conductance of each channel
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Tetrodotoxin
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blocks Na+ entry
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Saxitoxin
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blocks Na+ Entry
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4-aminopyridine (4AP)
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selectively block K+ channels = will prolong action potential.
- used for people with muscular weakness or disease at the NMJ |
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Anesthetics
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block Na+ channels on pain receptors
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safety factor
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every excitatory signal is ~5x as strong as is needs to be. therefore it can still move thru an demyelinated area
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Synaptic delay
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occurs between arrival of impulse at synaptic bouton (nerve ending) and response of postsynaptic cell;
related to speed of diffusion, but mostly affected by transmitter release (exocytosis). - Shorter in Ionotropic. Longer in Metabotropic |
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Which Neurotransmitter DIFFUSES out of synaptic cleft?
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neuropeptides
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Strychnine
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blocks glycine receptors in CNS - no inhibitory signals = muscle spasm and inference with breathing
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Morphine
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binds to receptors of neuropeptide on C fibers (pain fibers) located in substantia gelatinosa
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Cocaine
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blocks reuptake of dopamine, serotonin, norephinephrine = prolonged activity
prolonged stimulation = down regulation of receptors |
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Botulinum
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inhibits exocytosis by inhibiting docking of synaptic vesicles.
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Lambert-Eaton syndrome
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auto-immune disease characterized by muscle weakness due to attack on Ca2+ channels in motor nerve terminals.
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Neostigmine
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inhibits AchE in synaptic cleft allowing Ach concentration to remain high.
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Myasthenia gravis
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is auto-immune disease where anti-bodies recognize nAchR, reducing their number on end plate, resulting in condition where there is not enough cation channels to reach threshold.
- treated with neostigmine (also give atropine because achE is not good for Cardiovascular) |
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Merkel's disk
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receptor for touch discrimination
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Ruffini's Endings
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receptor for skin stretch
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Meissner's corpuscle
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receptor for vibration
- highest sensitivity - low frequency |
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Pacinian Corpuscle
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receptor for vibration
- high frequency - low sensitivity |
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Factors Contributing to High Spatial Resolution
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1. High density of cutaneous mechanoreceptors
2. Small receptive field 3. Large cortical area involved 4. Special mechanisms, ie. lateral inhibition |
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stereognosia
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ability to perceive properties of a coherent object, like its size, shape, texture, by holding it the hand
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The first sense lost in peripheral neuropathies is usually:
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vibration
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Tabes Dorsalis
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- Destruction of DRG cells with large diameter myelinated axons
- Consequence of Syphilitic infection - severe deficit in touch and proprioception (large diameter myelinated axons) - Nociception and temperature remain unaffected |
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Phantom limbs is due to:
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reorganization of the cortical maps
ie. touching the face induced sensations that were perceived to have originated from amputated hand - facial region takes over 'unused' cortex regions |
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Nociceptive Pain
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from stimuli that have the potential to cause tissue damage
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Neuropathic Pain
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pain sensation from aberrant somatosensory processing in the PNS or CNS
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First Pain vs. Second Pain
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First Pain
- myelinated Aδ fibers (faster) - sharp, pricking sensation - activation of thermal or mechanical nociceptors Second Pain - unmyelinated C fibers (slower) - burning sensation - activation of polymodal nociceptors |
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Visceral Pain is carried on what type of fiber?
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unmyelinated C fibers
- burning sensation |
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What activates three chemicals activate nociceptors?
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1. K+ from damaged cells
(intracellular K+ leaks into extracellular. will depolarize surrounding cells) 2. Bradykinin from blood 3. Histamine from mast cells |
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What 3 chemicals cause hyperalgesia?
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Hyperalgesia = increased sensitivity to pain after nociceptors have been activated
Leukotrienes - from damaged cells Prostaglandin - from damaged cells Substance P - from primary afferents |
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What are the effects of opioids?
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- ↓ duration of action potential from afferent neurons
- ↓ amplitude of excitatory post synaptic potential - hyperpolarize 2nd order neuron in pain pathway |
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How does aspirin regulate pain?
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It inhibits cyclo-oxygenase
cyclo-oxygenase is the enzyme responsible for the synthesis of Prostaglandins. - Prostaglandins increase pain sensitivity |
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Dorsal rhizotomy
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- surgical management of pain
- destroy dorsal root of spinal nerves |
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Miosis
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constricted pupil
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mydriasis
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dilated pupil
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What two structures in the eye are responsible for accommodation?
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Ciliary muscle and Zonule Fibers (suspensory ligaments)
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Optic disc
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- only axons of retinal ganglion cells
- no photoreceptors = blind spot - retina overlaying lamina cribrosa |
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Fovea
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highest visual acuity
- no rods, only cones - surrounded by macula - 1.5 mm diameter - all layers (except for photoreceptors) are pushed laterally so they don't interfere with photoreceptors - on ophthalmoscope = area without blood vessels |
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Macula
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- region of high acuity
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Refractive Power
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1/ focal length
unit = Diopter (D) |
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Far vision
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Ciliary Muscle - Relax
Zonule fiber - Tighten Lens = Flat - ↓ Refractive Power (13D) F - Far, Flat |
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Near Vision
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Ciliary Muscle Constricted
Zonule Fiber - Loose Lens = - Rounded (more convex) - ↑ refractive power (26D) |
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Presbyopia
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- inability to focus on near objects with age
- lens loose its elasticity with age |
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What is normal visual acuity?
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an angle of 5 minutes of a degree
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What factors determine visual acuity?
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- low threshold for 2 point discrimination
- high density of photoreceptors - proper functioning accommodation apparatus |
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Emmetropia
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normal sightedness
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Papilledema
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Optic Disk Edema
- Indicates ↑ Intracranial Pressure - compromised venous drainage = dilated retinal veins = optic disk pushed forward and appears white (instead of pink) |
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scotoma
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areas of lost visual acuity due to retinal detachment
ie. dead pixels |
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When looking at the ocular fundus, the optic disc is always on the ______ side.
a. Lateral b. Medial |
b. medial side.
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Macular Degeneration
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- loss of vision in macula due to damage to retina
- Neo-vascualr = abnormal blood vessel growth. Most severe type. - Treatment: Laser Photocoagulation - Leading cause of vision loss in US |
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Temporal Resolution
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ability to distinguish subsequent stimuli from each other (time related)
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Spatial Resolution
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ability to distinguish adjacent stimuli from each other (relating to space)
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Neurotransmitter for Photoreceptors
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Glutamate
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Which second messenger keeps the Na+ channel open in the dark current?
a. cAMP b. cGMP c. IP3 |
cGMP
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True/False
More glutamate is released from photoreceptors in the dark. |
true.
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There is more convergence in:
a. Rods b. Cones |
Rods have more convergence.
Cones have less convergence = better visual acuity |
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Retinal
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- light absorbing substance
- derived from Vitamin A |
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Superior Visual Field
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- temporal radiation
- below the calcarine sulcus |
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Infereior Visual Field
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- parietal radiation
- above the calcarine sulcus |
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Sparing of the macula
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- vascular damage usually involves posterior cerebral artery
- the macula region is also supplied by the middle cerebral artery and therefore it is usually spared |
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Color Agnosia
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inability to distinguish color hue
- lesion in area 17 or 18 |
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Ocular Dominance columns
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organization of primary visual cortex
- arranged in alternating contralateral/ipsilateral columns |
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Orientation columns
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- primary visual cortex shows preference for certain stimuli
- ie. horizontal or vertical |
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Magnocellular Pathway
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- Dorsal (parietal) pathway
- Depth & Motion (answers Where?) (Location & Movement) - detects fast moving stimulus - synapse in first 2 layers of lateral geniculate nucleus - Magno b/c larger cells |
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Parvocellular Pathway
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- Ventral (Temporal) pathway
- Form & Color (answers What?) - Color vision and acuity - projects deeper into the primary visual cortex - synapses in layers 3-6 (deeper and in more layers than magnocellular pathway) |
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otosklerosis
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replacement of normal bone in labyrinth and stapes footplate with lamellar new bone
= fusion of stapes with border of oval window. = conductive hearing loss ~ 40db |
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Vestibular schwannoma
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Causes sensorineural hearing loss
- benign tumor from Schwann cells - compresses vestibulo-cochlear nerve within internal meatus - symptoms = sensorineural hearing loss and tinnitus |
