Physiology of Hearing and Balance Flashcards
Which part of the ear is the sound collector?
external ear
Which part of the ear is the mechanical force amplifier?
middle ear
Which part of the ear is the transducer/analyser?
inner ear
Which part of the ear is shaped to receive sound?
external
In the middle ear, what does the ossicular chain act as?
“lever arm” with varying efficiency (depending on frequency of sound
What is the name of the bony and cartilaginous tube which is a ventilation pathway for middle ear mucosa?
eustachian tube
What is the resting state of the eustachian tube?
closed
What causes the eustachian tube to open?
tensor veli palatani and levator palatine muscles
What equalises the ear?
eustachian tube
What does dysfunction of the eustachian tube lead to?
middle ear negative pressure
What are the two openings of the cochlea to the middle ear?
oval window and round window
What do the two windows allow?
transmission of pressure wave in enclosed canal, and vibration of the basilar membrane
Which part of the ear has a curved spinal lamina with 2 and a half turns around its centre medially?
inner ear
In the cochlea, the scala media is suspended between what?
scala tympani and scala vestibuli
Where are the coiled tubes of liquid?
cochlea
What is the function of hair cells (stereocilia)?
transduction
turns bending force into an electrical impulse
How are stereocilia arranged?
in height order with tip links connection them together
What happens when the stereocilia are deflected towards the longest?
depolarisation in organ of corgi
What happens when stereocilia are deflected away from longest?
hyperpolarisation
What does depolarisation lead to?
8th nerve stimulation and activity in superior temporal gyrus
Describe the structure of the inner ear.
Complex labyrinth structure
bony and membranous
5 key vestibular end organs
How many otolith organs are there and what are they called?
2, utricle and saccule
What type of rotations do otolith organs perceive?
straight line
How many semicircular canals are there and what are they called?
3
ampullae of lateral, posterior and superior semicircular canals
What type of rotations do semicircular canal organs perceive?
head rotation (angular)
What degree of orientation is there in otolith organs?
360’
What degree of orientation is there in semicircular canal organs?
90’
What happens to stereocilia in semicircular canals?
bending causes stereocilia to deflect
What happens to stereocilia in otolith organs?
movements perceived by hyper or depolarisation of hairs - when movement stops, firing stops
Where does the cupula sit?
ampulla of SSC
What otoconia?
calcium carbonate crystals (related to otolith organs)
What is a vestibular schwannama?
tumour of VIII nerve sheath (schwann cells)
Why does imbalance occur in a vestibular schwannama?
slowly progressive loss of function
