blk5 wk2

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  1. dorsal column-medial lemniscal system
    • ascending: fine touch, position sense
    • Cell bodies in DRG -> dorsal horn -> dorsal columns
    • lower limbs/trunk: gracilis fasciculus
    • upper limbs/trunk: cuneate fasciculus
    • internal arcuate fibers, cross @ decussation of the medial lemniscus
    • synapse @ ventral posterior lateral (VPL) nucleus of thalamus
    • fibers go to primary somatosensory cortex of parietal lobe via posterior limb of internal capsule
  2. pathway of fine touch, proprioception from face
    • processed in brain stem, not spinal cord
    • afferents from skin have cell bodies in trigeminal ganglion
    • trigeminal nerve -> synapse in sensory/principal nucleus of the trigeminal complex in the pons
    • Decussation in pons, join trigeminothalamic tract (adj to medial lemniscus) -> synapse on ventral posterior medial (VPM) nucleus of thalamus
  3. anterolateral system
    • pain, temperature, coarse touch
    • cell bodies in DRG -> dorsal roots -> may ascend/descend 2-3 segments in Lissauer's tract (dorsolateral) before going deeper & synapsing in dorsal horn
    • Axons cross midline in anterior white commissure -> spinothalamic/anterolateral tract on contralateral side
    • dorsolateral to medial lemniscus
    • synapse in ventral posterior lateral (VPL) nucleus of thalamus
    • project to primary somatosensory cortex
  4. pathway of pain, temp, coarse touch from face
    • cell bodies in trigeminal ganglion & ganglia assoc. w/ VII, IX, X
    • Run w/those nerves into brainstem
    • Descend in spinal trigeminal tract -> synapse in spinal nucleus of the trigeminal complex (pas caudalis) in medulla
    • Decussate in medulla, join anterolateral tract
    • synapse in ventral posterior medial (VPM) nucleus of the thalamus
  5. corticospinal path
    • descending motor pathway, lateral
    • Primarily area 4 in cerebral cortex -> internal capsule -> central basis pedunculi -> diverge in basis pontis -> converge in pyramid of ventral medulla
    • Decussation of pyramids: fibers cross -> more dorsolateral
    • @ target level, synapse onto motorneurons or interneurons in ventral horn
    • 85% cross, 15% do not
  6. corticospinal path function
    • necessary for skilled movements of digits
    • voluntary, goal-directed movements
    • facilitatory effects on flexor muscles
  7. upper motor neuron syndrome
    • damage of multiple descending paths
    • eg - stroke, multiple sclerosis
    • paralysis
    • hyperreflexia, hypertonia (spasticity)
    • minimal/disuse atrophy
    • Babinski sign, extensor plantar response
  8. lower motor neuron syndrome
    • direct damage to alpha motor neurons innervating skeletal muscle
    • paralysis
    • hyporeflexia, hypotonia
    • atrophy
    • fibrillations, fasciculations
  9. spasticity
    • hyperreflexia
    • hypertonia: increased resistance to passive stretch, velocity dependent
    • clasp-knife lengthening rxn
    • clonus: rhythmic, alternating contractions
  10. pathway of CSF
    • choroid plexus
    • out of lateral ventricle thru foramen of Monro (interventricular)
    • into third ventricle
    • cerebral aqueduct to fourth ventricle
    • out midline of 4th ventricle thru foramen of Magendie, out lateral sides thru foramina of Luschka
    • eventually reabsorbed thru arachnoid villi
  11. cisterns
    • cisterna magna: between medulla and cerebellum
    • interpedunclar cistern: between cerebral peduncles
    • superior or quadrigeminal cistern: surrounds dorsal and lateral surface of midbrain
  12. pathway of blood thru brain
    • vertebral artery joins basilar artery which gives off:
    • posterior inferior cerebellar artery (PICA)
    • anterior inferior cerebellar artery (AICA)
    • superior cerebellar artery
    • 2 posterior cerebral arteries
    • internal carotid gives off:
    • anterior cerebral artery (into longitudinal fissure), connected by anterior communicating artery
    • posterior communicating artery, which connects w/ posterior cerebral artery
  13. corticobulbar fibers
    • descending inputs into motor cranial nerve nuclei
    • upper part of face receives bilateral innervation, lower is contralateral
    • contralateral lesions can produce mild/transitory weakness
    • fibers cross at level of facial nucleus
  14. oculomotor nucleus
    ptosis, diplopia
  15. trochlear nucleus
    diplopia, affected eye appears slightly elevated @ rest
  16. abducens (VI) nucleus
    • damage to nerve: medial deviation
    • damage to nucleus: cannot move contralateral eye medially when the other eye moves laterally, internuclear neurons not able to coordinate
    • MLF: medial longitudinal fasciculus, fibers go to oculomotor nucleus on the opposite side
  17. hypoglossal XII nucleus
    • loss of genioglossus fx on one side
    • tongue deviates toward weak side
  18. Edinger-Westphal nucleus
    • preganglionic neurons of parasympathetic, synapse in ciliary ganglia
    • postganglionic neurons innervate pupillary constrictor and ciliary muscles
    • travel w/III nerve
    • damage = mydriasis
    • needed for pupillary light reflex
  19. Trigeminal sensory nuclear complex
    • mesencephalic nucleus: Ia afferents from muscles of mastication/ mechanoreceptors have ccell bodies here
    • main sensory nucleus: tactile & proprioception, homologous to dorsal column nuclei
    • spinal nucleus: pain/temp fibers from spinal trigeminal tract
  20. special sensory nuclei: auditory (VIII) central pathway
    • vestibulocochlear nerve
    • enter brainstem near ponto-medullary jx
    • go to dorsal cochlear and ventral cochlear nuclei, near inf cerebellar peduncle in rostral medulla
    • cross, enter lateral lemniscus
    • trapezoid body
    • inferior colliculus in midbrain
    • medial geniculate
    • primary auditory cortex
  21. Chemotrigger zone
    • area postrema
    • emetic: D2-dopamine receptors, mu-opioid receptors, 5-HT3 serotonin receptors, and H1-histamine receptors
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blk5 wk2
neuro blk5 wk2
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