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269 Cards in this Set
- Front
- Back
Schwann cells
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Myelination of peripheral axons. Neural crest.
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Oligodendrocytes
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Myelination of CNS axons. Neuroectoderm.
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Sympathetic innervation of head and neck viscera
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T1 and T2 via superior cervical ganglion
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Sympathetic innervation of the heart
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T1 via cervicothoracic ganglion and T3
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Sympathetic innervation of the trachea, bronchi and lungs
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T1 via cervicothoracic ganglion and T3
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Sympathetic innervation of foregut and midgut
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T4, T5, T6
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Sympathetic innervation of cutaneous organs
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T7-T12
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Sympathetic innervation of smooth muscle and glands of hindgut and pelvic viscera
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L1, L2
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Parasympathetic innervation of pupillary sphincter
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III cranial nerve via ciliary ganglion
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Parasympathetic innervation of cilliary muscle
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III cranial nerve via ciliary ganglion
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Parasympathetic innervation of the submandibular and sublingual gland
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VII cranial nerve via submandibullar ganglion
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Parasympathetic innervation of lacrimal gland, nasal and oral mucosa
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VII cranial nerve via pterygopalatine ganglion
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Parasympathetic innervation of parotid gland
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IX cranial nerve via otic ganglion
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Parasympathetic innervation of thoracic and abdominal viscera
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X cranial nerve
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Parasympathetic innervation of hindgut and pelvic viscera
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S2-S4
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What are the 3 primary vesicles
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Forebrain, midbrain, hindbrain
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What are the 5 secondary vesicles
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Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon
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Derivations of the forebrain
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Telencephalon, diencephalon. "For TeD"
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Derivations of the midbrain
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Mesencephalon
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Derivations of the hindbrain
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Metencephalon, myelencephalon
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Derivations of the telencephalon
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Cerebral hemispheres, most basal ganglia, lateral ventricles
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Derivations of the diencephalon
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Thalamus, pineal gland, neurohypophysis, hypothalamus, retina, third ventricle
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Derivations of the mesencephalon
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Midbrain, cerebral aqueduct
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Derivations of the metencephalon
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Pons, cerebellum, fourth ventricle
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Derivations of the myelencephalon
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Medulla, fourth ventricle
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Anterograde axonal transport
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Through microtubules mediated by kinesin. Moves vesicles and proteins to axon terminal
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Retrograde axonal transport
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Through microtubules mediated by dynein. Transports lysosomes and recycled membrane
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What are the glia cells and whats their origin?
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Ependymal, astrocytes and oligodendrocytes. Neural tube origin.
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Ependymal cells
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Line the ventricles and have cilia that move CSF.
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Astrocytes
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Control the microenvironment of CNS neurons and participate in the blood-brain barrier
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Oligodendrocytes
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Form myelin for CNS axons
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Choroid plexus
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Produce CSF within the ventricles
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What are the four ventricles of the brain
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Lateral ventricles, third ventricle and fourth ventricle
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Communication between the lateral and third ventricles
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Via the interventricular foramen of Monro
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Communication between the third and fourth ventricles
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Via the cerebral aqueduct of Sylvius
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Location of the fourth ventricle
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Between the dorsal surfaces of pons and medulla and ventral surface of cerebellum
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Communication between the ventricles and the subarachnoid space
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Via the two lateral formania of Luschka and the median foramen of Magendie in the fourth ventricle
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CSF drainage into the venous system
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Occurs via arachnoid granulations into the superior sagital dural venous sinus
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Causes of communicating hydrocephalus
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Chroroid papilloma (oversecretion of CSF), subarachnoid tumors (limits circulation of CSF), meningitis (limits absorption into the superior sagital sinus)
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Causes of non-communicating hydrocephalus
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CSF obstruction at the foramen of Monro, aqueduct, foramen of Luschka or Magendie
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Blood-brain and CSF-brain barriers
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Formed by tight junctions between the capillary endothelial cells and epithelial cells of the choroid plexus. Astrocytes participate in the maintenance of the blood-brain barrier
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Subdural hematoma
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Caused by laceration of superior cerebral veins
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Epidural hematoma
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Caused by the laceration of middle meningeal artery
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Where are the bodies of the lower motoneuron?
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Ventral horn of the spinal cord and cranial nerve nuclei
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Where are the bodies of upper motoneurons?
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Cerebral cortex, red nucleus, reticular formation, lateral vestibular nuclei of the brain stem
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Origin of the corticospinal tract
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60% of its fibers are from the primary motor cortex and premotor area. 40% of its fibers are from primary and secondary somatosensory cortical areas of the parietal lobes.
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Corticospinal tract
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Axons leave the cortex in the internal capsule, descend through the ventral portion of the midbrain, pons and medulla and in the lower medulla 80-90% of the fibers cross to the contralateral side at the decussation of the pyramids. The tract descends the spinal cord in the lateral part of the white matter and synapse with the lower motoneurons in the ventral horns of the gray matter.
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Function of the corticospinal tract
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Voluntary refined movements of the distal extremities
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Muscle stretch reflexes
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Knee (L2-L4), ankle (S1), biceps (C5-C6), triceps (C7-C8)
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Alpha motoneurons
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Innervates motor units (extrafusal motor fibers)
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Gamma motoneurons
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Innervate intrafusal motor fibers that form the muscle spindle (sensory receptor/stretch reflexes)
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Signs of upper motoneuron lession
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Spastic paralysis, Paresis (ipsilateral or contralateral), hyperreflexia, hypertonia (decorticate or decerebrate rigidity), disuse atrophy, Babinski, all below the level of the lession
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Signs of lower motoneuron lession
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Flaccid paralysis, ipsilateral paresis, areflexia, fasciculations, atrophy at the level of the lession
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Decorticate rigidity
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Postural flexion of the arm and extension of the leg seen in lessions above the midbrain.
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Decerebrate rigidity
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Extension of the arm and leg in lessions below the midbrain
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Function of the dorsal column/medial lemniscus tract
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Mediates conscious proprioception, discriminative touch, vibration, pressure, joint and muscle position sensation
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Dorsal column/medial lemniscus tract
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First order neuron have bodies in the dorsal root ganglion (receptors are Meissner, Pacini, spindles and GTOs) ascends through the gracile fasciculus (medially, lower extremities) and the cuneatus fasciculus (lateral, upper extremities). Second order neurons are in the gracile and cuneatus nuclei of the lower medulla, where they decusate and form the medial lemniscus which ascends to the ventroposterolateral nucleus of the thlamus. Third order neurons go from the VPL nucleus through the posterior limb of the internal capsule to the primary somatosensory cortex (postcentral gyrus, parietal lobe)
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Romberg sign
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Patient places feet together. If the patient sways with closed eyes it suggests dorsal root lession. If the patient sways with open eyes it suggests cerebellar lession.
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Dorsal colum/medial lemniscus lession
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Loss of astereognosis (discriminatory sensation), joint possition (Romberg sign), pressure and vibration (tested using 128Hz tuning fork), in the ipsilateral side if below the medulla or contralateral if above the medulla.
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Function of the anterolateral spinothalamic tract
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Carries pain, temperature and crude touch sensations from extremities and trunk
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Anterolateral spinothalamic tract
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First order neurons are in the dorsal root ganglion and enter the spinal cord via A-delta (fast) and C fibers (slow) at the dorsolateral tract of Lissauer. Second order neurons are in the dorsal root gray matter and decusate in the ventral white commissure to the spinothalamic tract in the ventral part of lateral funiculus and to the VPL nucleus of the thalamus. Third order neurons are in the VPL nucleus to the primary somatosensory cortex in the postcentral gyrus of the parietal lobe. Ascend in the anterolateral brainstem
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Polio
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Bilateral destruction of lower motoneurons in the ventral horn. Flaccid paralysis, atrophy, areflexia, fasciculations.
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Amyotrophic lateral sclerosis (Lou Gehrig)
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Bilateral damage to corticospinal tract in cervical regions (lower limb spastic paralysis, hyperreflexia, babinski, disuse atrophy) and bilateral damage to ventral horns in cervical regions (upper limb flaccid paralysis, areflexia, atrophy).
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Occlusion of the anterior spinal artery
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Interrupts blood supply to ventrolateral parts of the cord (spinothalamic and corticospinal tracts). Bilateral spastic paresis and bilateral loss of temperature and pain below the lession.
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Syringomyelia
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Progressive cavitation of the central canal in cervical regions damages decusation of spinothalamic tract. Bilateral loss of pain and temperature in the hands and forearms. Can also damage ventral horns resulting in flaccid paralysis, areflexia, atrophy of upper limbs. Can be associated with Horner syndrome, hydrocephalus, Arnold Chiari malformation.
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Tabes dorsalis
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Manifestation of neurosyphilis. Bilateral damage to the dorsal roots and columns. Loss of astereognosis and proprioception, vibration and position sense. Positive Romberg, pain, ataxia, "high step stride". Associated with Argyll Robertson pupil.
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Subacute combined degeneration
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Due to B12 deficiency/pernicious anemia. Bilateral demyelination of the dorsal columns and corticospinal tract. Bilateral spastic paresis, hyperreflexia, disuse atrophy, babinski, bilateral loss of asterognosis, proprioception, joint position, ataxia (spinocerebellar tract involvement), autoantibodies against intrinsic factor.
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Multiple sclerosis
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Episodes of focal neurologic deficits with exacerbations and remissions may damage optic nerve, dorsal columns, corticospinal tracts, medial longitudinal fasciculus. Can present with spastic paresia, monocular blindness, paresthesias, ataxia.
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Brown-Sequard
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Hemisection of the cord damages corticospinal tract, spinothalamic tract, dorsal columns. Ipsilateral spastic paresis, Ipsilateral loss of asterognosis and proprioception, contralateral loss of pain and temperature senses one or two segments below the lession, and ipsilateral flaccid paralysis with loss of all sensation at the site of the lession.
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Cranial nerves of the midbrain
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Oculomotor (III), trochlear(IV)
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Cranial nerves of the pons
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Trigeminal (V), abducens (VI), facial (VII), vestibulocochlear (VIII)
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Cranial nerves of the medulla
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Glosopharyngeal (IX), vagus (X), hypoglossal (XII)
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Location of the substantia nigra
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Dopaminergic neurons in the ventral midbrain. Associated with Parkinson's.
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Irrigation of the brain stem
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Vertebrobasilar artery
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Functions of oculomotor nerve III
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Moves eyeball, adduction of the medial rectus, constricts pupil, accomodation of cilliary muscle, raises eyelid.
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Lesion of oculomotor nerve III
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External strabismus diplopia (medial rectus), loss of parallel gaze (medial rectus), midriasis (sphicter pupillae), loss of near response (ciliary muscle), ptosis (levator palpebrae superioris).
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Functions of the trochlear nerve IV
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Depresses the eye (superior oblique), intorts
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Lesion of the trochlear nerve IV
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Weakness looking down with adducted eye (superior oblique), trouble going downstairs, head tilts away from lesion
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Functions of abducens nerve VI
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Abducts eyeball (lateral rectus)
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Lesion of abducens nerve VI
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Internal strabismus diplopia, loss of parallel gaze
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Functions of the accesory nerve XI
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Turns head to opposite side (sternocleidomastoid), elevates and rotates scapula (trapezius)
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Lesion of the accesory nerve XI
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Weakness turning head to opposite side, shoulder drop.
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Functions of trigeminal ophthalmic nerve V1
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General sensation of forehead, scalp, cornea
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Functions of trigeminal maxillary nerve V2
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General sensation of palate, nasal cavity, maxillary face and teeth
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Functions of trigeminal mandibular nerve V3
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General sensation of anterior 2/3 of tongue, mandibular face and teeth, motor innervation to muscles of mastication (temporalis, masseter, medial and lateral pterygoids)
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Lesion of trigeminal nerve V
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V1 and V2: loss of sensation of forehead, scalp, maxilla, maxillary teeth; V3: loss of sensation in mandible, tongue and weakness cheweing with deviation of the jaw to affected side.
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Functions of the facial nerve VII
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Motor innervation to muscles of facial expression, sensation of anterior 2/3 of tongue, salivation (submandibular, sublingual glands), tears (lacrimal glands), makes mucus (nasal and palatine glands)
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Lesion of the facial nerve VII
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Corner of mouth droops, cant close eye, cant wrinkle forehead, loss of blink reflex, hyperacusis, alteration of taste, red and dry eyes.
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Functions of the glosopharyngeal nerve IX
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Sensation of the pharynx, carotid sinus, salivation (parotid gland), taste in the posterior 1/3 of the tongue
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Functions of the vagus nerve X
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Swallowing muscles, phonation muscles, sensation in the pharynx, laryngopharynx and GI tract, motor innervation of foregut and midgut, raises eyelid, dilates pupil, innervates sweat glands
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Lesion of the vagus nerve X
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Nasal speech, hoarseness, dysphagia, loss of gag and cough reflexes, uvula points away from affected site, Horner syndrome.
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Medial lemniscus
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Located medially within the brainstem. Contains axons from second order cell bodies of the dorsal column gracilis and cuneatus nuclei. Decusation occurs in the lower medulla. Proprioception, vibration, discriminative touch, pressure and joint position. Lesion of the ML in the brain stem affects contralateral side.
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Descending hypothalamic fibers
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Located lateral within the brainstem. Carry fibers from the hypothalamus through the brainstem to preganglionic sympathetics. Lesions produce Horner syndrome and might be associated with lesion of the anterolateral spinothalamic tract (contralateral loss of pain and temperature senses)
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Location of the spinothalamic tract and descending thalamic fibers in the brainstem
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Lateral and dorsolateral
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Location of the medial lemniscus in the brainstem
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Anteromedially
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Location of the corticospinal tract in the brainstem
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Ventromedially
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Distinguishing feature of the medulla in a path slide
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The olives in the ventral side. Send fibers into cerebellum through inferior peduncle
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Nuclei of the medulla
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Spinal nucleus and tract of V, solitary nucleus, nucleus ambiguus, dorsal motor nucleus of X, hypoglossal nucleus, accessory nucleus. (IX, X, XI, XII, V)
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Spinal nucleus and tract of CN V
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Located in the dorsolateral medulla and pons. The spinal tract of V goes from C2 to the V nucleus in the pons. This nucleus receives axons from afferent trigeminal pain and temperature fibers that enter the pons and descend to synapse in the spinal nucleus.
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Solitary nucleus
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Located dorsal and lateral to the XII nucleus in the medulla. Receives axons from visceral afferents (taste and sensation) carried by CN VII, IX, and X.
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Nucleus ambiguus
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Located dorsal to the inferior olive in the medulla. Give rise to motor efferents of CN X that supply soft palate, pharynx, larynx and upper esophagus. Lesion will produce ipsilateral paralysis of soft palate with uvula deviation away from affected side, nasal regurgitation of liquids, hoarseness and dysphagia.
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Dorsal motor nucleus of CN X
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Located lateral to the XII nucleus (dorsolateral) in the medulla. Supplies preganglionic parasympathetic fibers that innervate terminal ganglia of thorax, foregut and midgut.
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Hypoglossal nucleus
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Located near dorsal midline of the medulla. Axons to innervate tongue muscles except palatoglossus.
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Accessory nucleus
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Is located in the cervical column and ascends to the medulla where it exits with the X through the jugular foramen. The XI nerve innervates the sternocleidomastoid and trapezius muscles.
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Distinguishing feature of the pons in a path slide
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Large ventral enlargement that carries fibers from pontine nucleus to cerebellum in the middle cerebellar peduncle
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Abducens nucleus
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Near the midline in the floor of the fourth ventricle in the lower pons.
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Facial motor nucleus
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Located ventrolateral to the abducens nucleus in the lower pons.
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Superior olivary nucleus
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Located ventral to the CN VII nucleus in the pons. Receives auditory impulses from both ears by way of cochlear nuclei; projects to inferior coliculi.
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Vestibular nuclei
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Located near the posterior surface of the pontomedullary junction lateral to the abducens.
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Cochlear nuclei
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Dorsal and ventral cochlear nuclei are lateral to the vestibular nucleus at the pontomedullary junction
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What are the trigeminal nuclei
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Motor nucleus (upper pons), main sensory nucleus (upper pons), spinal trigeminal nucleus (spinal cord to upper pons), mesencephalic nucleus (midbrain)
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Motor nucleus of the CN V
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Located in the mid dorsolateral part of the upper pons. Innervates the muscles of mastication (masseter, temporalis, pterygoids)
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Main sensory nucleus of CN V
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Located in the mid dorsolateral part of the upper pons lateral to the motor nucleus of the CN V. Receives tactile and pressure sensation from the face scalp, oral and nasal cavity and dura.
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Mesencephalic nucleus of the CN V
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Located in the dorsal midbrain. Receives proprioception from joints, muscles of mastication, extraocular muscles and teeth.
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Inferior colliculus
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Located on the dorsal midbrain. Processes auditory information received from the choclear nuclei.
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Superior colliculus
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Located on the dorsal midbrain. Helps direct movements of both eyes in gaze.
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Oculomotor nucleus
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Located on the dorsomedial midbrain at the level of the superior colliculus. Contains preganglionic parasympathetic fibers from the Edinger-Westphal nucleus.
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Trochlear nucleus
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Located near posterior midline inferior to the inferior colliculi
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Corticobulbar fibers
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Upper motoneurons and innervate all cranial nerve motor nuclei (V, VII, X, XI, XII). Each nucleus receives bilateral cortex innervation.
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Trigeminal neuralgia
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Recurrent paroxysms of sharp stabbing pain in the course of a trigeminal branch on one side of the face. Rx.: carbamazepine
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Central facial paralysis
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Affects the lower part of the face. Drooping of the mouth contralateral to the lesion. Damage to corticobulbar (upper motoneuron) fibers.
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Peripheral facial paralysis
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Affects entire face. Drooping of the mouth, cant wrinkle forehead or shut eye on side of the lesion.
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Spiral ganglion
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Cell bodies of bipolar neurons innervate organ of corti on the peripheral side and form the cochlear part of the VIII nerve that enters the dorsal pontomedullary junction to the cochlear nucleus
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Auditory circuit
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Cochlear nerve enters the dorsal pontomedullary junction to the cochlear nucleus. Second order neurons from the cochlear nucleus bilaterally innervate the superior olivary nucleus of the pons. Fibers ascend in the lateral lemniscus to the inferior colliculus in the midbrain. Higher order neurons from the inferior colliculus to the medial geniculate body of the thalamus. Higher order neurons from the MGB of the thalamus to the primary auditory cortex on the posterior portion of the transverse temporal gyrus. Lesion below the cochlear nucleus results in ipsilateral hearing loss. Lesions above the superior olivary nucleus results in bilateral hearing loss.
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Weber test
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Vibration fork is placed on the vertex of the skull and patient hears it louder on the side of the lesion (conductive) or on the normal side (sensorineural). Only indicates that there's a lesion but does not differentiate.
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Rinne test
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Vibration fork is placed on the mastoid bone to bypass air conduction. Patient indicates wether they hear the vibration. Then fork is placed on the ear. If bone conduction was better than air conduction --> conduction hearing loss.
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Sensory receptors of the vestibular system
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Macula and utricles respond to linear acceleration and detects positional changes in the head relative to gravity. Semicircular ducts detect changes in angular acceleration resulting from circular movements of the head.
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Vestibulo-ocular reflex
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Secondary vestibular fibers from the vestibular nucleus supply the III, IV and VI nerves. Movement of the head to the right is perceived by the right semicircular ducts, increasing firing rate to the right vestibular nucleus which sends fibers to the ipsilateral oculomotor and the contralateral abducens. The result is adduction of the right eye by the oculomotor and abduction of the left eye by the abducens. Both eyes turn to the left.
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Lesion of the vestibular nucleus
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Produces deviation of both eyes to the side of the lesion
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Cold water in the ear
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Slow nystagmus to the side of the cool water and corrected fast nystagmus to the opposite side. "COWS": cold, opposite, warm, same.
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Warm water in the ear
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Slow nystagmus away from the water and corrected fast nystagmus to the side of the water. "COWS" cold, opposite, warm, same.
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Control centers of horizontal gaze
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First order neurons are in the frontal eye field which cross to the contralateral side to the paramedial pontine reticular formation in the pons. Second order neurons from the PPRF innervate the ipsilateral abducens nucleus and the contralateral oculomotor nucleus through the medial longitudinal fasciculus (MLF).
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Lesion of the frontal eye field
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Lateral gaze paralysis to the contralateral side because theres no innervation of PPRF, ipsilateral abducens and contralateral oculomotor.
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Lesion at the PPRF
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Ipsilateral lateral gaze paralysis because theres no innervation to ipsilateral abducens and contralateral oculomotor.
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Lesion to the medial longitudinal fasciculus
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Inability to adduct one eye on attempted gaze to the opposite side due to lack of PPRF innervation to oculomotor (ipsilateral to MLF and contralateral to PPRF)
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Branches of the vertebral artery
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Anterior spinal (ventrolateral 2/3 of cervical spine, ventrolateral medulla), posterior inferior cerebellar PICA (cerebellum, dorsolateral medulla)
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Irrigation of the medulla
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By branches of the vertebral artery: anterior spinal (ventrolateral medulla) and PICA (dorsolateral medulla)
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Basilar artery
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Formed by joining of the two vertebral arteries at the pontomedullary junction. Terminates at the upper pons by dividing into the posterior cerebral arteries. Branches are the AICA (dorsolateral lower pons), superior cerebellar artery (dorsolateral upper pons), and labyrinthine artery (follows CN VIII to inner ear).
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Irrigation of the pons
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By branches of the basillar artery: AICA (dorsolateral lower pons), superior cerebellar artery (dorsolateral upper pons) and paramedian arteries (median pons)
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Irrigation of the midbrain
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Paramedian and circumferential branches of the posterior cerebral arteries
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Medial medullary syndrome
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Occlusion of vertebral or anterior spinal arteries. Contralateral spastic hemiparesis (corticospinal tract), contralateral loss of proprioception, position and vibration (medial lemniscus) and ipsilateral tongue deviation (XII)
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Lateral medullary syndrome
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Occlusion of the PICA. Ipsilateral pain and temperature loss on the face (spinal V), contralateral pain and temperature loss (spinothalamic tract), vertigo and nystagmus away from lesion (vestibular nuclei), ipsilateral Horner syndrome (descending hypothalamic fibers), ipsilateral paralysis of vocal cords, dysphagia (nucleus ambiguus)
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Medial pontine syndrome
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By occlussion of the paramedial branches of the basilar artery. Contralateral loss of proprioception, vibration and pressure sense (medial lemniscus), contralateral spastic hemiparesis (corticospinal tract), medial strabisumus (abducens). May or may not involve facial nerve fibers (ipsilateral Bell's pasly).
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Lateral pontine syndrome
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By occlusion of the AICA (lower pons) or superior cerebellar artery (upper pons). Contralateral loss of pain and temperature (spinothalamic tract), ipsilateral pain and temperature loss in the face (spinal V), ipsilateral Horner syndrome (descending hypothalamic tract), ipsilateral facial paralysis (VII nucleus), vertigo and nystagmus away from the lesion (vestubular nucleus, lower pons), ipsilateral hearing loss (cochlear nucleus, lower pons), anesthesia of the face (V nucleus, upper pons)
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Pontocerebellar angle syndrome
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Caused by acoustic neuroma of CN VIII. Lateral pressure compresses CN VIII and anterior pressure compresses CN V.
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Medial midbrain (Weber) syndrome
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By occlusion of branches of posterior cerebral artery. Contralateral spastic hemiparesis (corticospinal tract), contralateral central facial paralysis (corticobulbar tract), mydriasis, ptosis, lateral strabismus (fibers of the III, oculomotor paralysis)
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Raphe nucleus
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Located in the midline from medulla to midbrain. Synthesizes serotonin and plays a role in mood, aggression and non-REM sleep. Degenerates in Alzheimer.
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Locus caeruleus
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Located in brainstem. Synthesizes norepinephrine and regulate arousal and attention. Degenerates in Alzheimer.
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Periaqueductal gray
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Nuclei surrounding the aqueduct in the midbrain. Cells have opiod receptors and descend to modulate pain in the dorsal horns of spinal cord.
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Superior rectus muscle of the eye
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Elevates, adducts, intorts. CN III.
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Inferior rectus muscle of the eye
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Depresses, abducts and extorts. CN III.
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Inferior oblique muscle of the eye
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Elevates, extorts, abducts. CN III.
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Levator palpebrae muscle of the eye
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Elevates upper eyelid. CN III.
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Constriction of the pupil
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Edinger-Westphal nucleus has preganglionic parasympathetics that travel with CN III to cilliary ganglion. Postganglionic fibers from the cilliary ganglion to the sphincter of the iris and cilliary muscle for accomodation.
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Superior oblique muscle of the eye
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Depresses, intorts, abducts. CN IV.
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CN IV paralysis
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Weakness of downward gaze, vertical diplopia, head tilts to compensate. Fibers of CN IV decusate on the dorsal midbrain.
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Corneal reflex
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CN V1 afferents are responsible
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Trigeminal damage features
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Hemianesthesia of the face, loss of corneal reflex, flaccid paralysis of mastication muscles, deviation of the jaw to the affected side, hypoacusis (deaf to low pitched sounds) due to paralysis of tensor tympani muscle, trigeminal neuralgia.
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Function of the cerebellar vermis
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Controls the axial and proximal musculature of the limbs. Input from spinal cord.
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Function of the intermediate cerebellar hemispheres
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Controls distal musculature. Input from spinal cord.
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Function of the lateral cerebellar hemispheres
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Motor planning. Input from cerebral cortex and inferior olivary nucleus
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Function of the floculonodular lobe
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Control of balance and eye movements. Input from vestibular nuclei. Output from fastigial nucleus to vestibular nucleus.
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What are Mossy fibers?
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Excitatory terminals on granule cells of the cerebellum. Input from vestibulocerebellar, spinocerebellar and corticopontocerebellar tracts.
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What are climbing fibers?
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Excitatory terminals on Purkinje cells of the cerebellum. Originate from the contralateral olivary nuclei of the medulla
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What are the layers of the cerebellar cortex?
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From the medulla outwards: granule cell layer, Purkinje layer and molecular layer.
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Molecular layer of the cerebellum
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Contains basket and stellate cells as well as the parallel axons of granule cells.
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Purkinje layer of the cerebellum
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Contains Purkinje cells which are the only ones to leave the cerebellar cortex to the deep cerebellar nuclei or to vestibular nuclei of the brain stem
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Granule cell layer of the cerebellum
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Innermost layer of the cortex, contains Golgi cells and granule cells.
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Purkinje cell of the cerebellum
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Inhibit deep cerebellar nuclei
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Granule cells
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Located in the granule cell layer of the cerebellar cortex, project axons to molecular layer which excite Purkinje cells
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Stellate cells
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Located in the molecular cell layer of the cerebellar cortex, inhibits Purkinje cells.
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Basket cells
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Located in the molecular layer of the cerebellar cortex, inhibit Purkinje cells.
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Golgi cells
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Located in the granular layer of the cerebellar cortex, inhibit granule cells.
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Deep cerebellar nuclei
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From medial to lateral: fastigial nucleus, interposed nuclei, dentate nucleus.
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Interpositus nucleus
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Receive input from Purkinje cells of the intermediate hemispheres. Output is to red nucleus and reticular formation of midbrain. Influences LMN via the reticulospinal and rubrospinal tracts.
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Fastigial nucleus
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Input from Purkinje cells of the vermis. Output to vestibular nucleus.
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Dentate nucleus
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Input from Purkinje cells of the lateral hemispheres. Output to VA and VL thalamus then cortex. Influences LMN via the corticospinal tract.
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Lesions of the vermis
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Gait or trucal ataxia with eyes open. Lesions from alcohol (anterior vermis) or medulloblastomas (posterior vermis)
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Lesions of the cerebellar hemisphere
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Ipsilateral intention tremor, dysmetria (finger-nose test), nystagmus
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Transection of the optic nerve
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Ipsilateral blindness with no direct pupillary light reflex (consensual reflex is conserved). Seen in multiple sclerosis.
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Bitemporal hemianopia
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Caused by midsagital pressure on optic chiasm (pituitary tumor).
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Binasal hemianopia
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Caused by bilateral lateral compression of optic chiasm by calcification or aneurysms of the internal carotid arteries.
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Optic tract
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Contains fibers from ipsilateral temporal retina and contralateral nasal retina (contralateral visual field). Projects to ipsilateral lateral geniculate body, pretectal nucleus and superior colliculus.
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Lesion of the optic tract
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Results in contralateral hemianopia (loss of contralateral visual field).
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Lateral geniculate body
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Upper division contains fibers from upper retina and project to the cunneus (lower visual field). Lower division contains fbers from lower retina and project via Meyer's loops to the ligual gyrus (superior visual field)
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Upper quadrantanopia
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Lesion of contralateral Meyer's loops that project to lingual gyrus.
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Lower quadrantanopia
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Lesion of the upper division of the contralateral lateral geniculate body and optic radiations
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Lesion of the cunneus or lingual gyrus
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Result in contralateral superior or inferior quadrantanopia with macular sparing
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Pupillary light reflex
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Afferents from optic nerve to pretectal area which sends axons to Edinger-Westphal nucleus on both sides. Edinger-Westphal nucleus sends preganglionic parasympathetics with CN III to cilliary ganglion.
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Accomodation
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Activation of Edinger-Westphal nucleus --> CN III --> cilliary ganglion --> cilliary muscle contraction --> lens becomes more round
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Convergence
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Contraction of both medial rectus muscles pulls eyes towards nose.
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Argyll-Robertson pupil
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Manifestation of neurosyphillis, multiple sclerosis, pineal tumors or tabes dorsalis. Eye accomodates but does not react to light.
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Nuclei of the thalamus
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Anterior nucleus, medial nucleus, ventral anterior, ventral lateral, ventral posterolateral, ventral posteromedial, medial geniculate body, lateral geniculate body, midline nucleus.
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Anterior nucleus of the thalamus
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Input from mammillary bodies and cingulate gyrus. Output to the cingulate gyrus.
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Medial nucleus of the thalamus
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Input from amygdala, prefrontal cortex, temporal lobe. Output to the prefrontal cortex and cingulate gyrus.
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Ventral anterior nucleus of the thalamus
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Input from internal segment of globus pallidus and substantia nigra. Output to premotor and primary motor cortex.
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Ventral lateral nucleus of the thalamus
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Input from globus pallidus and dentate nucleus of cerebellum. Output to the primary motor cortex.
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Ventral posterolateral nucleus of the thalamus
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Input from medial lemniscus and spinothalamic tracts. Output to primary somatosensory cortex.
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Ventral posteromedial nucleus of the thalamus
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Input from ascending trigeminal pathways. Output to primary somatosensory cortex.
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Medial geniculate body of the thalamus
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Auditory input from inferior colliculus. Output to primary auditory cortex.
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Lateral geniculate body of the thalamus
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Input from the optic tract. Output via visual radiations to primary visual cortex in occipital lobe.
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Midline and intralaminar nuclei of the thalamus
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Input from brain stem reticular formation and spinothalamic tract. Intralaminar nuclei send pain information to cingulate gyrus.
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Nuclei of the hypothalamus
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Paraventricular, supraoptic, suprachiasmatic, arcuate, ventromedial, mammillary bodies, anterior zone, lateral zone, preoptic area
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Paraventricular and supraoptic nuclei of the hypothalamus
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Synthesis of ADH and oxytocin to posterior pituitary.
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Suprachiasmatic nucleus of the hypothalamus
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Receives visual input from retina. Involved in circadian rhythm.
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Arcuate nucleus of the hypothalamus
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Dopaminergic projections inhibit prolactin release by adenohypofisis.
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Ventromedial nucleus of the hypothalamus
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Satiety center regulates food intake. Lesion results in obesity.
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Mammillary bodies of the hypothalamus
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Part of the limbic system. Lesions occur in Korsakoff syndrome due to thiamine deficiency in alcoholics.
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Anterior hypothalamic zone
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Senses elevations of body temperature and mediates response to dissipate heat. Lesions lead to hyperthermia.
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Posterior hypothalamic zone
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Senses decreases in body temperature and mediates conservation of heat.
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Lateral hypothalamic zone
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Feeding center. Lesions lead to aphagia.
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Preoptic area of the hypothalamus
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Sensitive to androgens and estrogens
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Pineal gland of the epithalamus
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Synthsizes melatonin, serotonin and CCK. Involved in growth, development and circadian rhythms. Pineal lesions in young males causes precocious puberty.
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Parinaud syndrome
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Compression of upper midbrain and pretectal area by pineal tumor results in impairment of conjugate vertical gaze and pupillary reflex abnormalities.
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Pineal tumor
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Communicating hydrocephalus and Parinaud syndrome.
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Components of the basal ganglia
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Striatum (caudate nucleus, putamen), globus pallidus, substantia nigra, subthalamus
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Function of the internal segment of globus pallidus
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GABAnergic neurons project to VA and VL thalamus which projects to motor cortex
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Function of the external segment of the globus pallidus
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GABAnergic neurons project to subthalamus (excitatory) which projects to internal segment of globus pallidus
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Direct basal ganglia pathway
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Glutaminergic motor cortex excites GABAnergic neurons of caudate nucleus and putamen which inhibit GABAnergic neurons in internal globus pallidus which in turn disinhibit VL and VA thalamus which excites the motor cortex. And produces movement.
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Indirect basal ganglia pathway
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Glutaminergic motor cortex excites GABAnergic neurons of caudate nucleus and putamen which inhibit GABAnergic neurons of external globus pallidus which disinhibits glutaminergic neurons of the subthalamus which excites GABAnergic neurons of internal globus pallidus which inhibit motor cortex and movement.
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What kind of neurons does the subthalamus have and where do they project?
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Excitatory glutaminergic neurons project to internal globus pallidus
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What kind of neurons does the VA and VL nuclei of thalamus have and where do they project?
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Excitatory glutaminergic neurons which project to the motor cortex
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What kind of neurons does globus pallidus, caudate nucleus and putamen have?
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Inhibitory GABAnergic neurons
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What is the net effect of the direct basal ganglia pathway?
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Excitation of the motor cortex through disinhibition of the VA and VL thalamus.
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What is the net effect of the indirect basal ganglia pathway?
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Inhibition of the motor cortex through disinhibition of subthalamus which stimulate the internal globus pallidus.
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Function of the substantia nigra
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Dopaminergic neurons project to caudate nucleus and putamen and activate direct basal ganglia pathway (D1 receptors) and inhibit indirect basal ganglia pathway (D2 receptors). Net effect is excitation of motor cortex.
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Cholinergic neurons in the striatum
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Activate the indirect basal ganglia pathway. Net effect is inhibition of the the motor cortex
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Involuntary movements: chorea
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Multiple, quick random movements due to atrophy of striatum. Associated with Huntington's.
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Involuntary movements: athetosis
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Slow, twisting movements due to diffuse hypermyelinization of the striatum and thalamus cerebral palsy.
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Involuntary movements: hemiballismus
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Wild flinging movements of half of the body due to hemorrhagic destruction of the contralateral subthalamic nucleus in hypertensive patients
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Involuntary movements: parkinsonism
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Fine resting tremor of the fingers, lead-pipe rigidity, akinesia due to degeneration of the substantia nigra
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Lesion of the subthalamic nucleus
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Contralateral hemiballismus due to affection of indirect basal ganglia pathway.
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Lesion of the striatum
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Result in chorea and athetosis
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Circle of Willis
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Formed by the branching of the basilar artery into cerebral posterior arteries and branching of internal carotid into anterior and middle cerebral arteries. Anterior communicating arteries are branches of the anterior cerebral artery and posterior communicating arteries are branches of posterior cerebral arteries.
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Opthalmic artery
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Branch of internal carotid artery just before bifurcation at the circle of Willis. Enters the orbit through optic canal.
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Middle cerebral artery
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Branch of the internal carotid. Supplies lateral surface of cortex except upper 1 inch of frontal and parietal lobes as well as inferior surface of temporal and occipital lobes. Also supplies posterior limb and genu of internal capsule and most of the basal ganglia.
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Occlusion of the middle cerebral artery
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Spastic paresis and anesthesia of contralateral lower face (corticobulbar tract) and upper limb (corticospinal tract); Aphasia if occlusion is on the left side; Contralateral superior quadrantanopsia (Meyer's loops); Asomatognosia if it's on the right side.
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Anterior cerebral artery
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Supplies medial surface of frontal and parietal, anterior 4/5 or corpus callosum and 1 inch of the superior and lateral aspects of the frontal and parietal lobes and anterior limb of internal capsule
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Occlusion of the anterior cerebral artery
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Spastic paresis and anesthesia of contralateral lower limb (corticospinal, anterolateral spinothalamic and medial lemniscus tracts), transcortical apraxia of the left limbs (anterior portion of corpus callosum).
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Posterior cerebral artery
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Arises from bifurcation of basilar artery and joins the carotid circulation via the posterior communicating arteries. Supplies inferior and lateral surfaces of occipital and temporal lobes, medial surface of occipital lobe and medial posterior 2/3 of temporal lobes as well as thalamus, subthalamus and splenium of corpus callosum.
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Occlusion of the posterior cerebral artery
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Results in contralateral homonymous hemianopia of the contralateral visual field with macular sparing. Might also present alexia without agraphia.
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Important areas of the frontal lobes
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Primary motor cortex in the precentral gyrus (area 4), premotor cortex anterior to the precentral gyrus (area 6), prefrontal cortex anterior to premotor cortex, frontal eye field anterior to the premotor cortex (area 8), Broca's area anterior to the premotor cortex (areas 44, 45).
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Motor homunculus
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From the lateral fisure to the medial surface of the frontal cortex: muscles of the neck, head, upper limb, trunk pelvis and lower limb. Pelvis and lower limb areas are irrigated by anterior cerebral artery, the rest by MCA.
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Functions of the premotor cortex
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Anterior to the precentral gyrus is responsible for the planning of motor activities. Damage results in apraxia.
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Functions of the prefrontal cortex
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Located anterior to the premotor cortex is responsible for planning and organizing the intellectual and emotional aspeects of behavior. Modulates the frontal cortex.
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Lesions in the prefrontal area
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Lack of concentration and distraction, apathy (emotional indifference), abulia (slow speech, slow cognition, lack of initiative), gras and/or suckling reflexes.
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Lesion of the frontal eye field
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No horizontal conjugate gaze to contralateral side with slow deviation of eyes towards side of lesion. Might be associated with contralateral spastic paresis.
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Expressive aphasia
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Motor, nonfluent aphasia due to lesion of Broca's area on the left or dominant hemisphere. Patient understands speech but can't express words verbally or written leading to frustration. May be associated with contralateral central facial paralysis and/or spastic hemiparesis and agraphia.
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Function of the posterior parietal association areas
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Posterior to the primary somatosensory cortex areas 5 and 7 are involved in interpreting sensory information.
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Primary somatosensory cortex
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Posterior to the central fissure of Rolando in the postcentral gyrus of the parietal lobes. Responsible for intepreting sensory information. Irrigated by anterior and middle cerebral arteries.
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Primary motor cortex
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Anterior to the fissure of Rolando in the precentral gyrus of the frontal lobes. Responsible for executing motor movements. Irrigated by anterior and middle cerebral arteries.
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Somatosensory homunculus
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From the lateral fissure to the medial surface of the parietal lobes: neck and tongue, face, thumb, hands, arms, trunk, hip and lower limbs.
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Apraxia
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Inability to execute learned motor movements such as brushing teeth or salute. Can be caused by lesions to the premotor cortex, posterior parietal association areas or corpus callosum (can be motor or sensory). Usually left brain damage.
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Types of aphasia
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Receptive (Wernicke), expressive (Broca), conduction, transcortical.
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Receptive aphasia
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Fluent, paraphasic aphasia due to lesion on Wernicke's area (22, 39, 40) on left hemisphere. Patient doesn't comprehend spoken or written language and speaks nonsense. Patient is unaware of deficit and show no distress.
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Gertsmann syndrome
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Lesion to angular gyrus area 39 results in alexia, acalculia, finger agnosia, right-left disorientation. Spoken language may be understood and spoken.
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Conduction aphasia
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Fluent, paraphasic aphasia due to lesion of the longitudinal fasciculus that connects Wernicke's area with Broca's area. Patient understands verbal and written language but speech is paraphasic with long word-finding pauses. The patient is aware and frustrated by the deficit.
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Transcortical apraxia
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Lesion of the corpus callosum due to occlussion of the anterior cerebral artery which disconnects Wernicke's area from right premotor cortex.. Patient understands commands but cannot make the corresponding movements with left arm.
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Asomatognosia
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Lesion to the right hemisphere at areas 7, 39, 40. Patient ignores and deny existence of left side of the body.
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Primary visual cortex
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Located on the occipital lobe. Receives input from lower retina (upper visual field) through the Meyer loop fibers and into the inferior ligual gyrus. Receives input from upper retina (lower visual field) via the visual radiations and into the upper cuneus gyrus. Irrigated by posterior cerebral artery.
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Alexia without agraphia
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Due to left posterior cerebral artery occlusion that affects the splenium of the corpus callosum (cannot send right visual field information to Wernicke's area on the left side) and the left visual cortex (cannot see the right visual field).
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Primary auditory cortex
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Areas 41 and 42 located on the superior and lateral aspect of the temporal lobe.
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Auditory association cortex
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Wernicke's area 22 located on the superior and lateral aspect of temporal lobe.
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Irrigation of internal capsule
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Anterior limb: anterior cerebral artery; genu and posterior limb: middle cerebral artery.
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Structures of the internal capsule
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Anterior limb has the thalamocortical tract; Genu has corticobulbar tract; Posterior limb has corticospinal and all somatosensory thalamic projections.
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Structures of the limbic system
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Hippocampus (medial aspect of temporal lobe), amygdala, mammillary bodies (hypothalamus), anterior and dorsomedial thalamic nuclei, cyngulate gyrus (medial surface of each hemisphere).
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Structures affected by Alzheimer's disease
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Locus caerulus (noradrenergic neurons), Raphe nucleus (serotoninergic neurons), hyppocampus (memmory)
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Lesion to medial aspect of temporal lobes
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Damage to hyppocampus produces anterograde amnesia.
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Wernicke-Korsakoff syndrome
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Due to thiamine deficiency in alcoholics. Wernicke encephalopathy: ocular palsies, confusion, gait ataxia. Korsakoff confabulation psychosis, anterograde and retrograde amnesia. Damage is to mammillary bodies and dorsomedial nucleus of thalamus.
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