Lecture 16- The ear: hearing and balance

Question 1

what is hearing?

Answer 1

our brains perception of sound energy

Question 2

what is sound transduction?

Answer 2

conversion of mechanical energy of sound waves to electrical energy

Question 3

what is pitch?

Answer 3

our interpretation of frequency

Question 4

what is loudness/ volume?

Answer 4

our perception of intensity/ amplitude of sound waves

Question 5

what does the processing of sound tell us?

Answer 5

tells us about distance direction and movement

Question 6

what are sound waves?

Answer 6

compressed air

Question 7

what structures are in the external ear? 3

Answer 7

pinna: directs sound waves into the ear
external auditory canal
tympanic membrane

Question 8

what structures are in the middle ear? 4

Answer 8

ossicles (malleus, incus, stapes)
eustachian tube (connects to pharynx/throat)

Question 9

what structures are in the inner ear? 5

Answer 9

semicircular canals
vestibular apparatus
oval window
cochlea
nerves

Question 10

what are the two different large overall structures of the inner ear?

Answer 10

bony labyrinth
membranous labyrinth

Question 11

what is the difference between bony labyrinth and membraneous labyrinth?

Answer 11

membranous labyrinth is located within bony labyrinth
membranous labyrinth is filled with fluid

Question 12

what does the membranous labyrinth contain?

Answer 12

cochlear duct with organ or corti
3 semicircular ducts with 1 crista ampullaris in each
utricle/saccule with 1 macula in each

Question 13

what happens when you hear sounds? what is the process?

Answer 13

1. sound waves strike the tympanic membrane and vibrates
2. vibration is transferred to the 3 bones of the middle ear
3. vibrations of the oval window create fluid waves within the cochlea
4. fluid waves cause hair cells to bend and ion channels to open which causes neurotransmitter release
5. neurotransmitter release onto sensory neurons creates AP that travel through cochlear nerve to brain
6. energy from waves transfers across the cochlear duct into the tympanic duct, then brought back into middle ear at the round window

Question 14

what is the process of hearing sounds through the cochlea in simple terms? Old Vegetables Help Tame Rabbits

Answer 14

oval window
vestibular duct
helicotrema (end of cochlea)
tympanic duct
round window

Question 15

what does the cochlear nerve do?

Answer 15

transmits action potentials from the primary auditory neurons to cochlear nuclei in the medulla on their way to the sensory cortex

Question 16

what are the 3 ducts that the cochlea has? what are they made of?

Answer 16

vestibular duct (contains perilymph that is extracellular fluid or plasma)
tympanic duct (contains perilymph that is extracellular fluid or plasma)
chochear duct (contains endolymph that has a high concentration of K+)

Question 17

what is the organ or corit? where is it located?

Answer 17

receptor organ of hearing
cochlear duct

Question 18

what structures are included in the organ of corti?

Answer 18

tectorial membrane
hair cells
nerve fibres
basilar membrane

Question 19

what is the structure of the hair cells?

Answer 19

stereocilia (look like toes) the tallest stereocilia is called the kinocilium (big toe) on the stereocilia are K+ channel proteins that are mechanically gated
connected by tiplinks

Question 20

what does happens when hair cells bend toward kinocilium?

Answer 20

excitatory: more channel proteins open, K+ entry depolarizes cell, thus have more action potential FREQUENCY which release more neurotransmitters

Question 21

what happens when hair cells bend away from kinocilium?

Answer 21

inhibition: channels close, less K+ entry, cell hyperpolarizes, frequency of AP decreases, thus less neurotransmitters released

Question 22

the basilar membrane has variable sensitivity to sound wave frequency along its length, describe the high frequency side and low frequency side

Answer 22

high pitch: stiff thicker region near round window
low pitch: flexible skinny region near helicotrema (end of cochlea)

Question 23

when sound leaves the cochlea what is the process through the brain?

Answer 23

vestibulocochlear nerve
medulla
midbrain
thalamus
cortex
OR
vestibulocochlear nerve
cerebellum

Question 24

what is conductive hearing loss?

Answer 24

loss of ability of ossicles to transmit vibration to oval window (external or middle)

Question 25

what is sensorineural hearing loss?

Answer 25

loss of ability of hair cells to respond to the movement of tectorial membrane generate electrical signals (middle ear)

Question 26

what is central hearing loss?

Answer 26

loss of ability of neural pathways from vesitibubchoclear nerve to CNS (stroke)

Question 27

where is the utricle/ saccule located in the inner ear?

Answer 27

inside vestibular apparatus/ vestibule

Question 28

what are the 2 compartments of the vestibular apparatus?

Answer 28

otolith organs
semicircular canals

Question 29

what does teh otolith organs consist of? 2

Answer 29

macula (sensory organ)
saccule/ utricle (detects linear acceleration and head position)

Question 30

what are the structures of the macula?

Answer 30

otoliths (crystals that move in response to gravitational forces)
gelatinous otolith membrane

Question 31

what do the semicircular canals consist of?

Answer 31

superior (sensitive to rotational acceleration)
horizontal (sensitive to rotational acceleration)
posterior (sensitive to rotational acceleration)
crista ampullaris

Question 32

what does the crista ampullaris do?

Answer 32

provides information about rotation of head
they rest on top of utricle and saccule