Lecom - Neuroanatomy 2: Neuroanatomy Overview And Basic Definitions

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Commissure

Back 1

Connects structures on right and left side of the CNS

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Six Cell Layers of Neocortex

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I. Molecular Layer - Dendrites and axons from other layers II. Small Pyramidal Layer - Cortical-Cortical Connections III. Medium Pyramidal Layer - Cortical-Cortical IV. Granular Layer - Receives inputs from Thalamus V. Large Pyramidal Layer - Sends outputs to subcortical structures (other than Thalamus) VI. Polymorphic Layer - Sends outputs to Thalamus

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Broadmann's Areas 1,2,3

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Primary Somatosensory Cortex

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Broadmann's Areas 4

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Primary Motor Cortex

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Broadmann's Areas 44

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Broca's Area

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Lesions of Cerebellum

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Disorders in coordination and balance - ATAXIA

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Lesions in Basal Ganglia

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Hypokinetic movement disorder - such as PARKINSONISM in which movements are infrequent slow and right Hyperkinetic movement disorders - such as Huntington's disease which is characterized by dancelike involuntary movements

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Thalamus

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Important relay center, almost all pathways that project to the cerebral cortex do so after synapsing in the thalamus

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Reticular Formation

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Extends throughout the central portions of the brainstem from medulla to the midbrain. More Caudal portions in medulla and lower pons tend to be involved mainly in motor and autonomic functions. Rostral reticular formation in the upper pons and midbrain plays important role in regulating level of consciousness. (Lesions that affect the pontomesencephalic reticular formation can cause lethargy and coma)

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Mass Lesions

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Mass lesions above the brainstem often cause impaired consciousness indirectly when they exert pressure on the brainstem through mass effect, thus distorting or compressing the reticular formation and thalamus

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LIMBIC SYSTEM

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Evolved from structures originally devoted to olfaction has a diverse function including regulation of emotions, memory, appetitive drives and autonomic and neuroendocrine control

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Areas of LIMBIC SYSTEM

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Certain cortical areas located in medial and anterior temporal lobes, anterior insula, inferior medial frontal lobes, and cingulate gyri, also hippocampal formation, amygdala, several nuclei in the medial thalamus, hypothalamus, basal ganglia, septal area, and brainstem

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FORNIX

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Paired arch-shaped white matter structure that connects the hippocampal formation to the hypothalamus and petal nuclei

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Lesions of Limbic System

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Cause deficits in consolidation of immediate recall into longer-term memories. No trouble recalling remote events but have difficulty forming new memories. Epileptic seizures most commonly arise from the limbic structures of medial temporal lobe.

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Unimodal

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higher-order processing takes place mostly for a single sensory or motor modality. Usually located adjacent to the primary visual cortex

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Heteromodal

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Involved in integrating functions from multiple sensory and or motor modalities

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Lesions in Wernicke's area

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Deficits in language comprehension also sometimes called RECEPTIVE or SENSORY APHASIA, or WERNICKE'S APHASIA

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Lesions in Broca's

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Deficits in production of language, with relative sparing of language comprehension…called expressive or motor aphasia or Broca's aphasia

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Lesions in the inferior partietal lobule in the left hemisphere

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Difficult with calculations, right-left confusion, inability to identify fingers by name (finger agnosia), difficulties with written language. (ALL KNOWN AS GERSTMANN'S SYNDROME)

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Apraxia

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Abnormalities in motor conceptualization, planning, and execution

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Anosognosia

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Unawareness of a deficit

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Extinction

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Tactile or visual stimulus is perceived normally when it is presented to one side only, but when presented on the side opposite the lesion simultaneously with an identical stimulus on the normal side, the patient neglects the stimulus on the side opposite the lesions.

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Lesions in Parietal Lobe

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Lesions especially in the nondominant hemisphere often cause a distortion of perceived space and neglect of the contralateral side..for example RIGHT parietal lesions can cause left hemineglect…with this syndrome patients will often ignore objects in their left visual field, but they may see them if their attention is strongly drawn to that side

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Frontal Release Signs

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Primitive reflexes that are normal in infants such as grasp, root, suck and snout reflexes but that can also be seen in adults with frontal lobe lesions

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Preservate

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Repeating a single action over and over without moving on to the next one

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Personality Chages with Frontal Lobe lesions

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impaired judgement, a cheerful lack of concern about one's illness, inappropriate joking and other disinhibited behaviors

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Abulic

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abnormal lack of ability to act or to make decisions

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Magnetic Gait

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Which shuffle close to the floor

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Lesions in Frontal Lobe

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Frontal release signs, difficulty when asked to perform a sequence of actions repeatedly or to change from one activity to another, and then tend to perserverate in doing tasks, impaired judgement, cheerful lack of concern about one's illness, inappropriate joking, disinhibited behaviors, abnormal lack of ability to act or to make decisions with a tendency to stare passively and to respond to commands only after a long delay, magenetic gait, urinary incontinence

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Prosopagnosia

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Inability to recognize faces

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Achromatopsia

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Inability to recognize colors

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Palinopsia

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Persistence or reappearance of an object viewed earlier

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Most common excitatory neurotransmitter in CNS?

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Glutamate

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Most common inhibitory neurotransmitter in CNS?

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GABA; glutamate-aminobutyric acid

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Main transmitter at neuromuscular junctions in the PNS?

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Acetylcholine

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Glutamate receptors and main action (3)

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AMPA/kainate - Excitatory neurotransmission



NMDA - Modulation of synaptic plasticity



Metabotropic - Activation of second messenger systerms

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In regards to where white matter vs gray matter is found in: cerebral hemispheres, spinal cord, brainstem

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Cerebral hemispheres - Gray on outside, white on inside

Spinal cord - Opposite is true

Brain stem- More mixed but most of outside surface is white matter

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What is white matter vs gray matter?

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White matter is mainly myelinated axons while gray matter is mostly cell bodies

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Dorsal nerve roots

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Mostly afferent sensory information into dorsal spinal cord

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Ventral nerve roots

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Mainly efferent motor signals from ventral spinal cord

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Where is the spinal cord thicker? Why?

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Brachial plexus and lumbosacral plexus because movement of arms and legs requires more signal flow. These areas have increased gray matter

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Sympathetic division arises from?

Parasympathetic?

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Sympathetic T1-L3

Parasympathetic S2-S4 and cranial nerves III, VII, IX, X

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The frontal lobes extend back to______ which separates it from the ______ lobe?

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The central sulcus of Ronaldo which separates it from the parietal lobe

Front 44

Frontal lobes are separated inferiorly and laterally from temporal lobes by?

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Sylvian (or lateral) fissure

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The primary motor cortex is where?

Back 45

In the precentral gyrus in the frontal lobe (controls opposite side of body)

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The primary somatosensory cortex is where?

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In the postcentral gyrus in the parietal lobe (gets information from opposite side of body)

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Corticospinal tract begins where? Crosses where?

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Begins in primary motor cortex and crosses over at the pyramidal decussation between the medulla and spinal cord

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Where do upper motor neurons synapse?

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Lower motor neurons which are located in the anterior horns of the central gray matter

Front 49

Lesions in the basal ganglia cause?

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Hypo and hyperkinetic movement disorders

(Parkinson's and Huntington's respectively)

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Output of the motor system is refined in mulitple feedback systems, the 2 most important are located where?

Where do these project to? How?

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Cerebellum and basal ganglia, project back to the motor cortex via the thalmus

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What do posterior column pathways convey? Where does the pathway cross?

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Proprioception, vibration, and fine touch. Crosses (and synapses) in medulla.

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What do anterolateral pathways convey?

Where does the pathway cross?

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Temperature, pain, and crude touch (Crude T-Pain). Crosses (and synapses) in spine.

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Where are the primary sensory neuron cell bodies located?

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Outside of the CNS in the dorsal root ganglia

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The posterior column and anterolateral pathways synapse where before going to the primary somatosensory cortex?

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Thalmus

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What sensory inputs are the exception and do not pass through the thalmus?

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Olfactory inputs

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Wernicke's area is located where? A lesion here would cause?

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Dominant (usually left) hemisphere. Lesion here would cause deficits in language comprehension (receptive or sensory aphasia)

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Broca's area is located where? A lesion here would cause?

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Located in the frontal lobe in the left hemisphere. Lesion here causes deficits in production of language (expressive or motor aphasia)

Broca's broken boca""

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Gerstmann's syndrome

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Lesion in inferior parietal lobule in left hemisphere. Difficulty with calculations, right-left confusion, finger agnosia, difficulties with written language

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Apraxia

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Difficulty in motor conceptualization, planning and execution. From diffuse lesions of the cortex or sometimes more focal lesions affecting the frontal or left parietal lobe

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Lesions in the nondominant hemisphere of the parietal lobe cause?

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Distortion of perceived space and neglect of the contralateral side

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Primitive reflexes that are normal only in infants may arise in an adult with what?

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Frontal lobe lesion

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What forms the anterior blood supply to the brain? Posterior supple?

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Internal carotid arteries form the anterior blood supply and the vertebral arteries which join to form the basilar artery supply the posterior brain

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Venous drainage of the brain is provided almost entirely by?

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Internal jugular veins

Front 64

Myelin forming glial cells in the CNS? In the PNS?

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In the CNS they are oligodendrocytes

In the PNS they are Schwann cells

Front 65

The primary auditory cortex is composed of what and located where?

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Composed of the transverse gyri of Heschl which are located in the inside the Sylvian fissure of the superior surface of each temporal lobe

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The primary visual cortex is where?

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In the occipital lobes along the banks of a deep sulcus called the calcarine fissure

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The right primary visual cortex is in charge of seeing what?

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The left visual fields of both eyes

Front 68

What are the cell layers of the neocortex?

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I Molecular

II Small pyramidal

III Medium pyramidal

IV Granular

V large pyramidal

VI polymorphic

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Which layer receives inputs from thalmus?

Back 69

IV Granular layer

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Which layer sends outputs to subcortical structures (other than the thalmus)?

Back 70

V Large pyramidal layer

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Which layer sends outputs to thalmus?

Back 71

VI polymorphic layer

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Which layers are the neurons in that project mainly to other sites of the cortex?

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II & III small and medium pyramidal layers

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Location and function of limbic system?

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Located near the medial edge of the cerebral cortex.

Regulates emotions, memory, appetitive drives and autonomic and neuroendocrine control

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Lesion in the limbic system?

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Difficulty forming new memories

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Lesion in frontal lobe?

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Frontal release signs (primitive reflexes), perseverate (repeat same action over and over), personality changes, abulic (stare passively, slow to respond to commands), MAGNETIC GAIT, urinary incontinence

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Lesion in visual cortex?

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Prosopagnosia (inability to recognize faces), palinopsia (reappearance of object viewed earlier), achromatopsia (inability to recognize colors)

Front 77

Monosynaptic Stretch Reflex

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Muscle Spindles - Detect amount and rate of stretch in muscles and carry it with Ia Afferent fiber, synapse in spinal gray matter on both an agonist muscle motor axon to cause contraction and an inhibitory interneuon on antagonist muscle to cause relaxation