T26-27 auditory & vestibular system

inner ear - blood supply

labyrinthine artery (branch of AICA)

labyrinthe - components

cochlea, vestibular labyrinth

helicotrema - connects

scala vestibuli & scala tympani

vestibular membrane (reissner’s membrane) - separates

scala vestibuli & cochlear duct

scala media - aka

cochlear duct

organ of corti - location

on basilar membrane, inside cochlear duct

modiolus - contains

spiral ganglion

modiolus - what

bony core of cochlea

cochlear n - first order neurons

bipolar cells (in spiral ganglion)

bipolar cells of spiral ganglion - parts

peripheral process (receive input from hair cells);

central processes (combine to form cochlear n)

cochlear n - second-order neurons

cochlear nuclei (in brainstem)

cochlear nuclei - specific location

medulla

cochlear nuclei - two parts

dorsal cochlear nuclei, ventral cochlear nuclei

ventral or dorsal cochlear nucleus - which one crosses

ventral cochlear nucleus

superior olivary nucleus - function

bilateral sound processing, localizing direction of sound

auditory radiations - location

sublenticular part of internal capsule

auditory association cortex - BA

BA 22, wernicke’s area

central auditory pathway - function

hear, recognize, interpret sound

descending auditory pathway - function

tune ear to focus on specific sounds, filter out background noise (cocktail party effect)

periolivary nuclei - part of

superior olivary complex

periolivary nucleus send sig to hair cells (of organ of corti) how

olivocochlear bundle via vestibular branch of CN8

acoustic reflex - aka

middle ear reflex

acoustic reflex - function

protect ear from loud sounds (include own voice)

acoustic reflex - trigger

loud sound input to superior olivary nucleus

conductive hearing loss - cause

blockage or damage to external or middle ear

otosclerosis - what

hardening of ligament around stapes bone

sensorineural hearing loss - cause

damage to inner ear, cochlea, or cochlear nerve

presbycusis - what

age-related degeneration of organ of Corti

central hearing loss - cause

damage to brainstem or cortical nuclei

lesion above cochlear nuclei - consequence

don’t cause hearing loss due to bilateral input

lesion at right cochlear nuclei - consequence

right-side hearing loss

rinne test - conductive hearing loss

problem with AC

rinne test - sensorineural hearing loss

problem with BC & AC

vestibular labyrinth - components

static labyrinth, kinetic labyrinth

static labyrinth - components & function

vestibule (saccule, utricle); detect head position

kinetic labyrinth - components & function

semicircular canals; detect head movement

urticle - detects

linear acceleration (horizontal)

saccule - detects

linear acceleration (verticle)

tilting of head - use what structures

utricle & saccule

semicircular canals - what part detects vertical rotation

superior (ant.) & posterior canals

semicircular canals - what part detects horizontal rotation

horizontal canals

vestibular nerve - first order neurons

vestibular ganglion (int. acoustic meatus)

vestibular nerve - second order neurons

vestibular nuclei (brainstem)

vestibular nuclei - name

superior, inferior, medial, lateral

vestibular nuclei - blood supply

branches of PICA

vestibular output to cerebellum - fibers

primary (direct) vestibulocerebellar fibers, secondary (indirect) vestibulocerebellar fibers

vestibular output to cerebellum - function

posture, balance, coordination of head & eye movement

how do fibers from vestibular nuclei go to brainstem

via MLF

vestibular output to brainstem - function

coordinate eye movement

vestibular output to brainstem - what cranial nerves

CN 3, CN4, CN6

vestibular nuclei input to thalamus - function

spacial orientation

medial vestibulospinal tract - function

neck muscles (head movement)

lateral vestibulospinal tract - function

extensor muscles for upright position

medial or lateral vestibulospinal tract - which one includes all levels

lateral vestibulospinal tract

vestibulo-ocular reflex (VOR) - function

keep gaze fixed on object while head or body moves

doll’s eye reflex - what

eyes don’t move in opposite direction of head (abnormal)

optokinetic nystagmus - cause

triggered when visual scene moves across retina (watch passing scenery)

end-gaze nystagmus - cause

when eyes are held at an extreme edge of gaze

vestibular neuritis/labyrinthitis - cause

inflammation of vestibular n. or inner ear from infection

meniere’s disease - cause

increased endolymph pressure in inner ear