Neuro Anatomy 2

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Neuro Anatomy 2
2011-05-27 11:56:07
Olfactory Vestibular tracts

anatomy of olfactory and vestibular tracts
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  1. components of the olfactory system
    • olfactory mucusa
    • olfactory N
    • olfactory bulbs
    • olfactory tracts
    • olfactory cortex
  2. olfactory mucosa
    • in sphenoethmoid recess
    • PSCC epithelium
    • contains olfactory (bowman's) glands- secrete fluid
    • olfactory cells-olfactory receptors, bipolar, constantly replaced, unmyelinated
  3. olfactory nerves
    • axons of olfactory cells
    • enter cranial cavity thru cribiform foramina of ethmoid bone
    • terminate in olfactory bulb as glomeruli
  4. olfactory bulbs
    • extension of the brain
    • made mainly of mitral cells- innervate glomeruli
    • few tufted cells-also innervate glomeruli
  5. olfactory tract
    • mostly mitral cells, few tufted
    • most lead thru lateral olfactory stria, few to anterior perforated surface
  6. lateral olfactory area
    • input thru lateral olfactory stria, makes primary olfactory area
    • uncus- anterior parahippocampal gyrus)
    • limen insula
    • amygdala
    • allows you to experience smells
  7. olfactory association area
    • alows identification of odors
    • adjacent to primary olfactory cortex
  8. anterior perforated substance
    • between lateral and medial olfactory stria
    • neurons connect to limbic structures
    • not incolved in concious olfaction
  9. olfaction influences on emotions, memory, and autonomic function
    • olfactory neurons project to areas of cerebral cortex, hypothalamus, and reticular system
    • influence emotional and visceral status of an individual
  10. testing olfactory system
    • each nostil should be tested separately
    • use recognizable odor
    • non-irritative odor, otherwise you would be testing pain receptors
  11. loss of smell
  12. causes of olfactory injuries
    • fractures of ethmoid bone
    • meningioma in floor of anterior cranial fossa
    • olfactory hallucinations
  13. uncinate seizures
    • convulsive movements of lips and tongue
    • disagreable olfactory hallucinations
    • confusion
  14. external ear
    • pinna- auricula
    • external auditory meatus- bony
    • external auditory canal- fleshy + bony
    • collects air vibrations and transmits them to the tympanic membrane
  15. middle ear
    • tympanic membrane
    • malleus
    • incus
    • stapes
    • oval window
    • round window
    • vibrations transferred thru ossicular chain to oval window
  16. muscles of middle ear
    • tensor tympani (trigeminal N)
    • stapedius (facial N)
    • dampen loud noises/vibrations
  17. inner ear- osseous labyrinth
    • tunnels in the petris temporal bone
    • filled with perilymph
    • semicircular canals- posterior part
    • vestibule- middle part
    • cochlea- anterior part (2 3/4) turns
  18. inner ear- membranous labyrinth
    • membrane tubes in osseous labyrinth
    • filled with enodlymph
    • semicircular ducts- within semicircular canals
    • utricle- connects to semicircular ducts
    • saccule- connects to cochlear ducts via ductus reunions
    • cochlear duct
  19. cochlear canal
    • scala media- cochlear duct, middle space
    • scala vestibuli-- superior to scala media, filled with perilymph, continuous with oval window
    • scala tympani- inferior to scala media, filled with perilymph, continuous with scala vestibuli at helicotreme, continous with round window
  20. cochlear duct
    • scala media
    • vestibular membrane- b/t scala media and vestibuli
    • stria vascularis- epithelial lining over vasculature, outer wall, produces endolymph
    • basilar membrane- b/t scala media and tympani, includes organ of corti
  21. organ of corti
    • mechanoreceptor
    • support cells- border cells, phalangeal cells, pillar cells, and cells of hensen
    • tectorial membrane- gelatinous membrane along organ of corti, tips of hair cells embedded here
    • sensory cells
  22. inner hair cells
    • single row
    • attached to chochlear nerve
    • principal sensory cells
  23. outer hair cells
    • three rows at basal turn increasing to five rows at apex
    • innervated by chochlear nerve
  24. tonotopical organization of organ of corti
    • high pitch- along basal turn
    • low pitch- apical end
  25. auditory pathways- primary neuron
    • cell bodies in spiral ganglia
    • peripheral processes innervate hair cells
    • central processes make cochlear division of VIII N, terminate in cochlear nucleus
  26. auditory pathways- secondary neurons
    • cell bodies in cochlear nuclei
    • processes project thru central auditory pathway
  27. contralateral auditory pathway
    • axons project to contralateral side of pons
    • -form the trapezoid body
    • -some terminate in superior olivary nucleus
    • -ascending fibers form lateral lemniscus, terminate in inferior colliculus, thru inferior brachium, into medial geniculate body of thalamus. axons thru internal capsule to form auditory radiations in primary auditory cortex
  28. ipsilateral auditory pathway
    • secondary neurons in cochlear nucleus project to ipsilateral suprior olivary nucleus
    • thru ipsilateral lateral lemnisculs, inferior colliculus, inferior brachium, medial geniculate body, and auditory radiations
  29. auditory cortex
    • primary auditory cortex in floor of the lateral sulcus
    • Heschl's gyrus- hears sounds, in transverse temporal gyrus
    • brodmann's area 41, 42
    • high hertz= medial
    • low hertz= lateral
  30. auditory association cortex
    • temporal lobe surrounding heschl's gyrus
    • brodmann's area 22
    • recognition and interpretation of sounds
  31. significance of bilateral pathway
    unilateral damage above cochlear nuclei results in decresed hearing in both ears, but not total loss of hearing
  32. general function sof vestibular system
    • maintain body equilibrium- posture and balance
    • coordinate eye movements
  33. saccule and utricle
    • parts of membranous labyrinth filled with endolymph
    • each contains a macula- sensory epithelium, mechanoreceptors
  34. morphology of the macula
    • hair cells- stereocilia projections with a single kinocilium embedded into the otolithic membrane
    • otolithic membrane- gelatinous membrane with otolithes- crystals of protein and calcium carbonate
    • dendrites of primary vestibular neurons- cell bodies in vestibular ganglion
  35. macula monitors which types of movement?
    tilting movements in a linear plane
  36. anterior semicircular duct is oriented in which plane?
  37. lateral semicircular duct is oriented in which plane?
    30 degrees to the horizontal
  38. ampulla
    • dilation at end of duct
    • lateral semicircular duct has anterior ampulla
    • contains crista ampullaris
  39. crista ampullaris
    • mechanoreceptor for angular/rotational movement
    • hair cells- stereocilia with single kinocilium embedded in cupula
    • vestibular neurons in vestibular gangion
  40. ampullopedal flow of endolymph
    flow toward the ampulla from the duct
  41. ampullofugal flow
    flow away from the ampulla thru the duct
  42. flow of enodlymph in lateral duct
    • ampullopedal movemnt facilitates crista
    • ampullofugal movement inhibits crista
  43. what happens to the discharge of crista when the head maintains rotation at a constant velocity?
    no net movement of endolymph so discharge returns to static rate
  44. vestibulospinal tract
    • major motor control pathway
    • ipsilateral
    • terminates on interneurons or motor neurons
  45. descending medial longitudinal fasciculus
    • ipsilateral and contralateral (bilateral)
    • most terminate in cervical segments to influence neck muscles
  46. ascending medial longitudinal fesciculus
    • permits visual fixation on stationary targets
    • ipsilateral and contralateral
    • influence cranial nerves VI, IV, and III
    • allows both eyes to move together
  47. vestibular information to the archicerebellum influences:
    • posture and balance
    • neurons to vestibular nuclear complex, to vestibulospinal tract
  48. vestibulo-ocular/ vestibulokinetic reflex
    • eyes slowly drift to the left (fixation on a target)- mediated by MLF
    • eyes quickly move to the right (fixation on a new target)- not vestibular driven
  49. nystagmus
    fast-slow eye movements
  50. roatation test of vestibular system
    • patient seated, head tilted forward 30 degrees, rotate at a constant velocity to the RIGHT
    • continue until crista reach static discharge, stop chair and have patient stand and focus on stationary object
    • eyes should display left nystagmus, patient will fall to the right, past point to the right of the object
  51. Caloric test
    • patient tilts head backwards 60 degrees
    • irrigate external auditory meatus with warm or cool water
    • response is COWS
    • cool water= fast drift to opposite side
    • warm water= fast drift to same side