Auditory, Vestibular, Olfaction, and Taste Systems

Question 1

auditory system gross anatomy

Answer 1

Question 2

otic capsule gross anatomy

Answer 2

Question 3

what is the membranous labyrinth filled with

Answer 3

endolymph, which has a higher potassium concentration and lower sodium concentration

Question 4

what is the bony labyrinth filled with?

Answer 4

perilymph, resembles extracellular fluid and CSF

Question 5

how is the membranous labyrinth contained in the bony labyrinth?

Answer 5

suspended within it by spiral ligament and delicate filaments

Question 6

how sound waves move through gross auditory system

Answer 6

sound waves vibrate tympanic membrane
vibrations transmitted through ossicles of middle ear
base of stapes vibrates at oval window
pressure waves in the perilymph of scala vestibuli
displacement of basilar membrane of the cochlear duct, bending hair cells of organ of Corti to stimulate action potentials
vibrations transferred across cochlear duct to perilymph of scala tympani
pressure wave dissipated by secondary tympanic membrane at the round window

Question 7

where is the organ of Corti located?

Answer 7

within the cochlear duct that is between the vestibular and tympanic canal

Question 8

what kinds of hair cells are found within the organ of Corti?

Answer 8

inner and outer hair cells

Question 9

what are inner hair cells? what do they do?

Answer 9

single row of hair cells innervated by up to 10 nerve fibers
detect frequency and fine discrimination of sounds

Question 10

what are outer hair cells? what do they do?

Answer 10

efferent structures of 3 to 4 rows, with 1 nerve fiber reaching multiple cells
modulate sensitivity of organ of Corti by changing their length in response to sounds

Question 11

can hair cells heal?

Answer 11

no! cannot regenerate either

Question 12

how are sound frequencies organized in the cochlea

Answer 12

low frequencies at the tip of the apex, high frequencies at the base

Question 13

how can hearing loss occur?

Answer 13

can be selective where a certain part of the cochlea is damaged, would only experience hearing loss for certain frequencies

Question 14

where are cell bodies for the primary sensory neurons of sound located?

Answer 14

the spiral ganglion

Question 15

auditory pathway, DCN

Answer 15

neurons sent to dorsal cochlear nucleus at pontomedullary junction
decussate after dorsal cochlear nucleus and ascend in the lateral lemnicus to inferior colliculus
from inferior colliculus, bilateral projections go to medial geniculate nucleus
from MGN, project to primary auditory cortex as auditory radiations

Question 16

where is the primary auditory cortex

Answer 16

anterior transverse temporal gyrus

Question 17

auditory pathway, VCN

Answer 17

neurons to ventral cochlear nucleus
from VCN, bilateral projections to superior olivary nuclear complex
from SONC, bilateral projections to inferior colliculus
from IC, bilateral projections to medial geniculate nucleus
from MGN to primary auditory cortex via auditory radiations

Question 18

what does the superior olivary nuclear complex do?

Answer 18

functions in localizing sounds horizontally in space

Question 19

where do auditory fibers decussate?

Answer 19

trapezoid body
this intersects with the medial lemniscus

Question 20

where will a lesion be for there to be unilateral auditory symptoms?

Answer 20

cochlear nuclei or nerve

Question 21

past the cochlear nuclei, what would a lesion of the auditory system cause?

Answer 21

issues localizing and interpreting sound

Question 22

what artery supplies the cochlear nuclei?

Answer 22

AICA

Question 23

some neurons in the superior olivary complex project back to where? why?

Answer 23

to the cochlea
to influence the basilar membrane via outer hair cells

Question 24

where are the secondary and higher-order auditory cortices located? what activates them?

Answer 24

around the primary auditory cortex, forming a belt
activated by complex sounds

Question 25

what are the 5 vestibular sensory organs in the vestibular labyrinth?

Answer 25

utricle and saccule (linear acceleration and gravitational positioning) 3 semicircular canals (angular acceleration)

Question 26

what are the utricle and saccule?

Answer 26

ovoidal sacs of membranous labyrinth, full of endolymph

Question 27

what is the macula of the vestibular system?

Answer 27

patch of hair cells in each organ, covered by otolithic membrane

Question 28

what is the otolithic membrane?

Answer 28

gelatinous sheet covered in otoliths (calcium carbonate particles)

Question 29

what does motion of the head cause?

Answer 29

shifting of the otolithic membrane, deflects the hair bundles and excites the hair cells

Question 30

what do the utricle and saccule detect

Answer 30

utricle - horizontal acceleration saccule - vertical acceleration

Question 31

what do semicircular canals respond to

Answer 31

rotational motion in one of three rotational planes - movement of endolymph only

Question 32

what is the cupula

Answer 32

gelatinous diaphragm that interrupts the endolymphatic space at the ampulla of each semicircular duct

Question 33

what excites the cupula

Answer 33

movement of endolymph against the cupula excites the hair bundles that penetrate the cupula

Question 34

medial longitudinal fasciculus

Answer 34

bilateral connections with CN III, IV, VI and superior colliculus, influence eye movement

Question 35

vestibulospinal tracts

Answer 35

medial (C spinal cord) and lateral (limbs and trunk) tracts influence posture

Question 36

vestibulocolic pathways

Answer 36

CN XI nucleus, influences head position

Question 37

vestibulothalamocortical

Answer 37

conscious awareness of head position/movement and input to influence corticospinal tracts

Question 38

vestibulocerebellar

Answer 38

controls magnitude of muscle responses to vestibular information

Question 39

vestibuloreticular

Answer 39

reticulospinal tract influence and autonomic centers for nausea and vomiting

Question 40

what is benign paroxysmal positional vertigo

Answer 40

acute onset vertigo and nystagmus following rapid head movement that subsides within 2 minutes

Question 41

what causes benign paroxysmal positional vertigo

Answer 41

displacement of otoliths into a semicircular canal movement causes abnormal flow of endolymph

Question 42

what repositioning maneuvers are used for benign paroxysmal positional vertigo?

Answer 42

Dix-Hallpike - diagnosis Epley - treatment

Question 43

why are semicircular canals insensitive to gravitational orientation and linear acceleration under normal conditions?

Answer 43

because endolymph and the cupula have the same specific gravity

Question 44

what is Ménière's disease?

Answer 44

aka idiopathic endolymphatic hydrops increased pressure of the endolymph system, causes expansion of the membranous labyrinth

Question 45

what are the symptoms of Ménière's disease

Answer 45

fluctuating hearing loss occasional episodic vertigo tinnitus aural fullness

Question 46

what does the taste system identify

Answer 46

nutrients/toxins ingested

Question 47

what receives information from taste receptor cells? what do they do?

Answer 47

primary afferent nerve fibers receive info from taste receptor cells, encode the info as action potentials

Question 48

taste pathway

Answer 48

CN VII, IX, X to rostral solitary nucleus through central tegmental tract to ventral posterior medial nucleus to gustatory cortex in insular and frontal operculum

Question 49

what are the secondary projection neurons of the olfaction system

Answer 49

mitral and tufted cells

Question 50

where do the secondary projection neurons synapse

Answer 50

in olfactory glomeruli

Question 51

what does the anterior olfactory nucleus do

Answer 51

modulates info in the olfactory bulb, contains bilateral connections via medial olfactory stria functions in early olfactory processing and feedback

Question 52

what do the amygdala and olfactory tubercle do in the olfaction pathway?

Answer 52

emotional, endocrine, and visceral consequences of odors

Question 53

what does the piriform cortex do

Answer 53

olfactory perception

Question 54

what does the entorhinal cortex do

Answer 54

olfactory memories