11 - The ear and hearing Flashcards
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changes the tension between the bones in situations to stop damage
tympani muscle
connecting the bones for transmission of a sound wave
auditory tube
makes the pressure in middle and outer ear equal for efficiency
What is the cochlea?
vestibular canal- scalar vestibuli
cochlear duct- scalar media
tympanic canal- scalar tympani
organ of corti- detects sound and transmits it into the nerves and brain
Where would you find the perilymph?
fluid in vestibular and tympanic canals
Where would you find the endolymph?
fluid in cochlear duct with more potassium ions
what happens in the basilar membrane?
From the base to apex the size increases and the frequency increases, becoming more floppy.
Vibrates from the sound.
What happens in the organ of corti?
- 3 rows of outer hair cells and 1 row of inner hair cells
- 40-80 stereo cilia on apical surface of each hair cell that projects into the tectorial membrane.
- tectorial membrane has gelatinous fluid
- hair cells detect vibration connected to nerve and tectorial membrane.
How does the mechanical stimulation turn to an electrical signal?
1) Basilar membrane vibrates
2) stereocilia bend
3) hair cell is depolarised
4) neurotransmitter released
5) sensory neurones are activated
6) message is conveyed to the brain via the cochlear branch of the vestibulocochlear nerve
semicircular canals
bony on the outside.
Endolymph filled membrane inside
Macula
Information on head position, acceleration and
deceleration
What can cause a hearing defect and how can it be solved?
Hair cells may be damaged or not formed properly.
An artificial cochlear is used:
-Receiver gets a high pitched noise and the electrode triggers a signal that creates a nerve impulse to the brain.
-A wire goes up the spiral and connects to the receiver and outside transmitter.
Detection of head position, acceleration and deceleration
Stereocilia movement Transduction channel Open = depolarisation Closed = repolarisation Signal sent via Vestibular branch of Vestibulocochlear nerve.
What is the physiology of balance?
- The semi-circular canal is filled with endolymph fluid.
- There are two macula, one in utricle and one in saccule.
- A forward tilt pulls on the hairs in the macula so the impulse tells the brain you are tilted.
What are semi-circular ducts?
They have multiple ampulla for each dimension (laterally, up/down) that detect the endolymph fluid.
They have a cupula with gelatinous fluid and hair that detects endolymph movement.