Mod 22 - Special Senses: Hearing and Balance

What is sound

Vibrations in the air

How does volume affect waves

Amplitude

How does pitch affect waves

frequency

What is the cerumen and what does it do

ear wax and it protects the ear

What is the auricle

ear lobe

What is the channel in the outer ear

External auditory canal

What is the tympanic membrane

Eardrum

Membrane that vibrates when waves reach it

What are the 3 auditory ossicles

malleus, incus, stapes

What do auditory ossicle do

amplify sound waves

What does the oval window do

connect to the cochlea

What do the semicircular canals do

dynamic equilibrium

whether our head is accelerating or decelerating

What does the vestibule do

Static balance

head position relative to ground

What does the round window do

where the sound waves leave the cochlea

What does the auditory tube do

Allows pressure of inner ear be equal to pressure in auditory canal

what does the membranous labyrinth do

Divide endolymph and perilymph

What has high k+ and low Na+

endolymph

What has high Na+ and low K

Perilymph

What is the helicotrema

End of cochlea

Difference between Scala vestibuli and Scala tympani

Vestibuli is top

Tympani is bottom

What fluid is in the Scala vestibuli and tympani

perilymph

What does the vestibular membrane seperate

Scala vestibuli and cochlear duct

What does the basilar membrane separate

Cochlear duct and Scala tympani

What is the tectorial membrane

sits over spiral organ region where the hair cells attach to

steps in the physiology of hearing

1. sound waves enter external auditory canal and hit the tympanic membrane

2. vibration is transferred to middle ear

3. Foot plate of the stapes vibrates in the oval window

4. Vibration causes perilymph in scala vestibuli to vibrate

5. Vibration of perilymph causes the vestibular membrane to vibrate -> vibrations in endolymph and basilar membrane -> movement of basilar membrane is detected by hair cells

6. Vibrations from scala vestibuli and basilar membrane are transferred to the perilymph of the scala tympani

7. Vibrations in the scala tympani are transferred to the round window

What are the 3 types of cells in the spiral organ and their function

supporting cells - support

Outer hair cells - regulate tension on basilar membrane

Inner hair cell - hair cells that detect sound

What is the microvilli on the hair cell called

stereocilia

What is a tip-link

little spring that attaches to ion gate of next stereocilium

What type of ion gated channel is a tip-link

mechanical

What ion causes depolarization of the basial membrane

potassium

How does depolarization of the inner ear work

stereocilia bend toward taller stereocilia causing the gated spring to stretch open so K+ can enter the cell

Where do high pitch waves get stimulated

close to round window

Where do low pitch waves get stimulated

close to the helicotrema

How are lower and higher volume waves stimulates

Lower - less hair cells

Higher - more hair cells

Two parts to vestibule

utricle and saccule

How does static labyrinth work

Hair cells are stimulated by otoliths

As otoliths move to gravity, action potential changes

Muscles of back and neck make adjustments

How does dynamic labyrinth work

Cupula moves in response to change in movements

Cupula moves in the way of direction (inertia)

Neural pathway for hearing

1. cochlear nerve

2. cochlear nuclei

3. inferior colliculus

4. Medial geniculate nuclei

5. primary auditory cortex

Neural Pathway for balance

1. vestibular nerve

2. vestibular nuclei

3. thalamus

4. vestibular area of cortex