1 - physiology of hearing & balance Flashcards
what is pathway of hearing (basic)?
sound to ear →goes through tympanic membrane (ear drum) →passes along auditory ossicles (malleus, incus, stapes) →through to semi circular tubules & cochlea & vestibule
what is basic idea of external, middle and inner ear function?
external = receiver of sound
middle = amplifier of sound
inner = translates sound (hair cells in organ of corti sway & open ion channel gates making depolarisation trigerring auditory nerve)
what are the compartments of coiled tube in inner ea?
- central one = scala media (important for hearing →contains endolymph
- scala tympani
- scala vestibuli →contains perilymph
- parts of vestibule between semicircular ducts & cochlea
what part of cochlea are different frequencies percieved?
high frequency = perceived at base
low frequency = perceived at apex
what nerve translates sound up to brain?
CN VIII (vestibulocochlear) translated up to posterior superior temporal gyrus
what is eustachian tube?
tube connecting back of nose & ear = equalises air pressure
what muscles can open eustachian tube?
tensor veli patani & levator palatine
what is structure of vestibule?
between semicircular canals (3) and cochlea = made of urticle & saccule
what is vestibulo-ocular reflex? explain normal? explain if tilt head while looking forward
involuntary reflex that helps stabilise your vision when move your head
normally = fluid in these isn’t moving but if head moves, fluid moves (helps brain understand movement
when turn head left, left side has more fluid movement & increases firing of hair cells, on right side has less so decreases firing = brain interprets difference to move eyes left to maintain focused point
what are the central pathways and what are they for?
- vestibulospinal tract (motor output to neck, back, help stay upright)
- medial longitudinal fasciculus & ocular muscles (vestibular ocular reflex, gaze stabilisation)
- medial lemniscus & thalamus to cerebrum (gives awareness of balance)
