Auditory Senses (Lec 6)

Question 1

What is the conduction pathway sequence?

Answer 1

tympanic membrane, malleus, incus, stapes, oval window

Question 2

The tympanic membrane surface area is about 17 X that of the surface of the stapes. This increases the force from the ossicular lever system to the cochlear fluid by how much?

Answer 2

22X; fluid has greater inertia than air and requires this increase in force in order to cause vibration in fluid

Question 3

What do the tympanic membrane and auditory ossicles provide?

Answer 3

the impedance matching between the air and fluid

Question 4

Tensor tympani is a small muscle in the ear, what does it do?

Answer 4

pulls handle of malleus inward

Question 5

What does the stapedius muscle do?

Answer 5

pulls stapes outward

Question 6

What are the major components of the cochlea?

Answer 6

scala vestibuli, scala media, scala tympani, reissner’s membrane; these make up the three tubes

Question 7

What two structures does Reissner’s membrane separate?

Answer 7

scala media from scala vestibuli

Question 8

What two structures does the basilar membrane separate ?

Answer 8

scala media from scala tympani

Question 9

The basilar membrane contains 20,000 to 30,000 fibers that project from the modiolus of the cochlea to what?

Answer 9

the outer wall

Question 10

Distal ends of the fibers are not fixed but are embedded in the basilar membrane, which allows the fibers to ____

Answer 10

vibrate

Question 11

Describe how the length and diameter of the basilar fiber changes between oval window and apex of cochleas

Answer 11

length increases from the oval window to the apex of the cochlea

diameter of the fibers decrease from oval window to the apex of the cochlea

Question 12

Where does high frequency of the basilar membrane occur?

Answer 12

near the oval window

Question 13

where does low frequency of the basilar membrane occur?

Answer 13

near the apex of the cochlea

Question 14

What is the function of the organ of corti?

Answer 14

generates nerve impulses in response to vibration of basilar membrane

Question 15

What are the sensory receptors of organ of corti?

Answer 15

hair cells

Question 16

Bending of the hairs in the organ of corti in one direction depolarizes them and bending them in the opposite direction does what?

Answer 16

hyperpolarizes them

Question 17

Neurons in the ganglion of the organ of corgi send axons via the cochlear nerve into where?

Answer 17

the upper level of the medulla

Question 18

Whenever basilar membrane moves, hair cells become ___

Answer 18

excited

Question 19

Each hair cell has about how many sterocilia on its apical border?

Answer 19

100

Question 20

Sterocilia are longer on the side farther from the ___

Answer 20

modiolus

Question 21

When cilia are bent in direction of the longer ones, a tensile force is created on the shorter cilia. This creates a mechanical transduction that opens what?

Answer 21

200-300 K+ channels resulting in depolarization of the hair cell membrane

Question 22

What is endolymph?

Answer 22

fills scala media; endolymph contains a high concentration of K+ and a low concentration of Na+

Question 23

Tops of hair cells project through the reticular lamina and are bathed in what?

Answer 23

endolymph

Question 24

Lower bodies of hair cells are surrounded by what?

Answer 24

perilymph

Question 25

What are the intracellular potentials of hair cells caused by endolymph vs. perilymph?

Answer 25

• 150 with respect to endolymph

- 70 with respect to perilymph

Question 26

What is place principle?

Answer 26

nervous system detects sound frequencies by determining positions along the basilar membrane that are most stimulated

Question 27

Where is the primary auditory cortex located?

Answer 27

Superior temporal gyrus in temporal lobe