MNSR 28 - Structure of the ear

Question 1

what does the outer ear consist of?

Answer 1

the pinna

Question 2

function of pinna

Answer 2

collects the sound and amplifies sound into the auditory canal
links the outer and middle ear
transmits sound waves into the skull

Question 3

tympanic membrane/ear drums

Answer 3

thin connective tissue converts sound waves into physical vibrations in the membrane

Question 4

what does the middle ear consist of?

Answer 4

tympanic membrane
tympanic cavity
ossicles (malleus, incus, stapes)
oval window
round window
auditory tube
stabilizing ligaments
eustachian tube

Question 5

function of stabilizing ligaments

Answer 5

hold ossicles in place

Question 6

smallest bone in the human body

Answer 6

stapes

Question 7

functions of eustachian tube

Answer 7

connects middle ear and back of nasal pharynx cavity
help w/ secretions of middle ear to be released through nasal pharynx
equalise pressure

Question 8

function of ossicles

Answer 8

transmit vibrations from the ear drum to the inner ear

translates the low-pressure movement of the large eardrum into high-pressure movement of the small oval window

Question 9

purpose of malleus/hammer ossicle in particular

Answer 9

connects to the eardrum on one side and the incus bone on the other
takes the vibrational energy of the eardrum and transfers it to the incus.

Question 10

function of incus

Answer 10

transfers the energy to the stapes

Question 11

features of inner ear

Answer 11

semi circular canals

cochlea

Question 12

how are parts of the semi circular canal and cochlea divided

Answer 12

outer - bony labyrinth

inner - membranous labyrinth

Question 13

bony labyrinth function

Answer 13

provides bony covering for membranous fluid

Question 14

membranous labyrinth description

Answer 14

A system of fluid-filled chambers and channels

Question 15

function of perilymph fluid

Answer 15

separates and covers the membranous and bony labyrinth

Question 16

2 systems in the inner ear

Answer 16

vestibular system

cochlea system

Question 17

function of vestibular system

Answer 17

provides us with our sense of balance and spatial awareness.

Question 18

which structure transmits sound waves from the outer ear to the middle ear?

Answer 18

tympanic membrane
pinna - collect and amplify sound in canal
and transmit sound wave to skull

Question 19

what does vestibular system consist of and their purpose?

Answer 19

semi circular canals - detect rotation

otholith organs - detect linear acceleration

Question 20

what does each canal in the semi circular canal contain?

Answer 20

each canal is filled w/ endolymph fluid
has a sac - osseous ampulla at one end
base of sac crista ampullaris

Question 21

three planes for semi circular canal

Answer 21

roll - x axis (front and back)
pitch - y axis (lean from side to side)
yaw - z axis (left to right)

Question 22

how do canals detect movement and know movement of head

Answer 22

move head - endolymph fluid move crista ampullaris is activated stimulates pull on crista ampullaris
sends impulse to vestibular nerve then to brain
nerve impulse from brain allows us to regain our balance

Question 23

function of crista ampullaris

Answer 23

translates flow of endolymph to nerve signals

Question 24

what does crista ampullaris consist of?

Answer 24

cupula - a gelatinous structure with hair cells at the base

Question 25

describe direction of cupula and endolymph as the body is moving

Answer 25

endolymph and cupula move in opposite direction of the body

Question 26

how does cupula help transmit signal to vestibular nerve

Answer 26

movement of cupula in opposite direction of body triggers membrane depolarisation of hair cells and transmit signals through nerves

Question 27

name the 2 otolith organs

Answer 27

utricle
smaller - saccule
both filled with endolymph

Question 28

function of 2 otolith organs

Answer 28

detect linear acceleration

Question 29

what type of movement does the utricle detect

Answer 29

horizontal movement

Question 30

what type of movement does saccule detect

Answer 30

vertical acceleration

Question 31

otoliths

Answer 31

crystals / ear stones on top of gel layer which has hair cells embedded in gel like substance which trigger nerve cells when the body moves

Question 32

3 canals of cochlea

Answer 32

scala vestibuli
scala tympana
scala media

Question 33

what is the scala vestibuli connected to?

Answer 33

connected to the oval window and thus the stapes

Question 34

what is the scala tympana connected to?

Answer 34

connected to round window

Question 35

what is helicotrema connected to?

Answer 35

connects scala tympani and scala vestibuli at the apex

Question 36

what do both scala tympani and scala vestibuli both contain

Answer 36

perilymph fluid

Question 37

what is the scala media (canal between scala vestibuli and scala tympana) connected to?

Answer 37

connected to saccule and contains endolymph

Question 38

what separates scala media from scala vestibuli

Answer 38

vestibular membrane

Question 39

what separates scala media from scala tympani

Answer 39

basilar membrane

Question 40

how is sound waves interpreted as sound

Answer 40

sound vibrations from oval window set up pressure waves in scala vestibuli and scala media
sound waves - waves in fluid cause basilar membrane to move up and down
central structure - organ of corti
basilar membrane bouncers off tectorial membrane over organ of corti and triggers hair cells in organ of corti
open K and Ca channels to enter cell
triggers release of glutamate
activate postsynaptic cochlear nerves

Question 41

how do basilar fibres change towards helicotrema and why

Answer 41

fibres become taller and thinner towards the helicotrema allows cochlea to pick up sound waves of different pitches and frequencies

Question 42

where will cochlea pick up high freq.
mid freg.
low freq.

Answer 42

high freq. - near base
mid freq - in middle
low freq - near apex