L20: Special sense II (hearing and equilibrium)

What part of ear vibrates in response to sound waves?

Tympanic membrane

What does malleus do?

Receives vibrations from tympanic membrane

What does incus do?

Transfers vibrations from malleus to stapes

What does stapes do?

Pushes on oval window

What does stapedius do?

Contracts reflexively in response to loud sounds which reduces sound transmission to inner ear

What does tensor tympani do?

Tenses tympanic membrane—active during chewing and swallowing

What are 2 ways middle ear increases pressure?

1. Large tympanic membrane—> smaller stapes footplate

2. Ossicles give lever action

What is the function of increased pressure?

Improves sound transfer into cochlear fluid

What does oval window do?

Transfer vibrations into fluid of inner ear

What does round window do?

Helps relieve pressure as cochlear fluid moves

What does Eustachian tube connect?

Middle ear to nasopharynx

What does Eustachian tube do?

Equalizes aire pressure across tympanic membrane

What is organ of corti?

In cochlea—houses sensory hair cells

What is inner ear function?

Converts vibrations into nerve signals

What is the bony labyrinth?

Bony cavities within temporal bone

What does bony labyrinth surround?

Membranous labyrinth

What is in space between membranous labyrinth and bony labyrinth?

Perilymph

What are semi-circular canals?

3 loop-shaped canals involved in detecting rotational head movements

What is vestibule?

Central region involved in balance and head position

What fills membranous labyrinth?

Endolymph

What does endolymphatic duct do?

Connects membranous labyrinth to endolymphatic sac

What does endolymphatic sac do?

Helps regulate endolymph volume/composition

What is the helicotrema?

Opening at tip of cochlea where scala vestibuli and scala tympani connect