Physiology of Hearing and Balance Flashcards
What is sound?
a pressure wave caused by oscillating molecules which are set in motion by a vibration
What does frequency dictate?
pitch
what does amplitude dictate?
intensity
What is the function of the middle ear?
amplifier
Why does the middle ear need to amplify sound?
Because there is a change from air sound waves to fluid waves. With this change there is a loss of energy, so the middle ear acts to minimise this change in energy between impendances
How does the middle ear amplify sound?
The ear drum is about 20 times bigger than the oval window, so the sound pressure in air is concentrated through the ossicles into the small oval window, increasing the sound pressure, the lever action- differences in lengths of the piston of the stapes and handle of malleus also does this
What muscles open the eustachian tube?
tensor veli palatini and levator palatine
What is the function fo the eustachian tube?
to equalise the ears
What type of fluid is the endolymph like compared to the perilymph?
endolymph is like ICF whereas perilymph is like ECF
What is the purpose of endolymph?
it helps support the hair cells by being high in potassium
What is the purpose of the inner hair cells?
sound perception
What is the purpose of the outer hair cells?
regulate and modulate sound that foes in- dont perceive soudn
What is transduction?
conversion of mechanical bending force into electrical impulse
How are the stereocilia arranged?
in height order with tip links connecting them together
What happens when the stereocilia move?
gap junctions are opened which let ions in and depolarise/hyperpolarise creating an AP
How is depolarisation of the cilia created?
when the cilia are deflected towards the longest
when does hyperpolarisation of the cilia happen?
when deflected away from the longest
What is the tonotopic organisation of the cochlea?
the basilar membrane is continuously graded in order to respond to different frequencies of sound
What frequency of sound is received at the base?
high frequency
What frequency of sound is received at the apex?
low frequency
What is the mnemonic for the central pathway of hearing?
E- eighth nerve C-cochlear nucleus O - superior Olivary complex L-lateral meniscus I-inferior colliculus
Where is the inferior colliculus found?
superior temporal gyrus
What are hte 3 things that contribute to balance?
ears; eyes; proprioception
What are the maculae of the utricle and saccule?
otolith organs
What are the 2 functions of the otolith organs?
sense linear acceleration (movement in a straight line) and sense the heads position in gravity
What is found in the membrane of the otolith organs?
otoconia- calcium carbonate crystals
What is the purpose of the otoconia?
give the gel extra mass and gravity pulls on the cystals so when the gravitional pull changes because the head has moved, they sense this.
How do the hair cells in the otolith organs detect movement?
they bend which opens the gap junctions and lets in potassium which depolarises the cell
How do the otolith organs detect movemnent in all planes?
the hair cells are orientated in all directions
What type of motion does the saccule detect?
vertical plane
What type of motion does the utricle detect?
horizontal plane
What is the push-pull orientation?
The semi-circular canals are paired to one on the other side of the head which means that when one canals hair cell potential is increased, the other is decreased
What is the cupula?
a membrane in the ampulla which the sterocilia project into
What is the purpose of the vesitbulo-ocular reflex?
stabilise the retinal image during the rotation of the head
What type of movement does the posterior canal detect?
head tilt to the left or right (tilting head to touch shoulder)
What type of movement does the superior canal detect?
front to back- nodding
What type of movement does the horizontal canal detect?
shaking of head
What is the vestibulospinal tract?
motor output to neck, back and leg muscles
What is the purpose of the pathway of medial lemniscus and thalamus to cerebrum
some central control/override
What is the medial longitudinal fasciculus and ocular muscle pathway for?
motor output to eyes
How are hair cells organised in the utricle compared to the saccule in relation to the matrix?
saccule- are arranged away from the matrix; in the utricle are arranged towards the matrix
