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Undeleted > Lecture 6 > Flashcards

Lecture 6 Flashcards

0
Q

What is bigger typanic membrane surface or area of stapes?

A

Tympanic membrane surface area is about 17 times that of the surface area of the stapes… 55mm to 3.2 mm -This increases the force from the ossicular lever system to the cochlear fluid by 22X -Fluid has greater inertia than air and requires this increase in force in order to cause vibration in the fluid

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1
Q

What is the conduction pathway sequence?

A

tympanic membrane… malleus…. incus…. stapes…. oval window

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2
Q

What do tympanic membrane and auditory ossicles provide?

A

the impedance matching btw the air and the fluid

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3
Q

How would hearing sensitivity be affected in the absence of the ossicular system and the tympanic membrane?

A

….

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4
Q

What does the tympani muscle do?

A

pulls handle of malleus inward

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5
Q

What does the stapedius muscle do?

A

pulls stapes outward

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6
Q

What effect do the above two opposing forces cause the ossicular system?

A

…

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7
Q

What is the function of this system( the attenuation reflex)?

A

…

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8
Q

What effect do these two muscles have on a person’s sensitivity to his or her own speech?

A

…

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9
Q

What consists of three side by side coiled tubes?

A

cochlea

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10
Q

What are the major components of the cochlea?

A

scala vestiviuli scala media scala tympani reissner’s membrane

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11
Q

What does the Reissner’s membrane do? (vestibular membrane)

A

separates scala media from scala vestibuli

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12
Q

What does the reissner’s membrane maintain?

A

a special fluid within the scala media

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13
Q

Because of the thinness of Reissner’s membrane?

A

the scala media and vestibuli are considered to be a single chamber as far as sound conduction is concerned

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14
Q

What does the basilar membrane separate?

A

scala media from scala typani

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15
Q

What does the basilar membrane consist of?

A

contains 20,000 to 30,000 fibers that project from the modiolus of the cochlea to the outer wall

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16
Q

Can the fibers of the Bailar membrane vibrate?

A

Yes

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17
Q

How are the fibers in the basilar membrane attached?

A

Distal ends of the fibers are not fixed but are embedded in the basilar membrane.

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18
Q

What does the length of the basilar fibers do from the oval window to the apex of the cochlea (helicotrema)?

A

the length increases

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19
Q

What happens to the length of the fibers from the oval window to the apex of the cochlea?

A

The fibers decrease.

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20
Q

What is the result of the short fibers near the oval window?

A

The stiff short fibers near the oval window be at a high frequency

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21
Q

What is the effect of the long fibers near the oval window?

A

The long limber fibers near the apex of the vibration at a low frequency.

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22
Q

Where does the high-frequency residents of the basilar membrane occur?

A

Near the base

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23
Q

Where does the low-frequency residents of the basilar membrane occur?

A

Near the apex helicotrema

24
Q

What does the organ of corti generate?

A

It generates the nerve impulses in response to vibration of the basilar membrane

25
Q

What are the sensor receptors of the organ of Corti

A

hair cells

26
Q

Single row of internal hair cells:

A

3500;12 um dia

27
Q

3-4 rows of external hair cells

A

12000; 8 um dia

28
Q

What does the hair cells stimulate in the organ of Corti

A

Hair cells stimulate nerve fibers that lead to the spiral ganglion of corti

29
Q

What do stereocilia from the hair cells do?

A

touch or are embedded in the overlying tectorial membrane

30
Q

What does bending of the hair do?

A

Bending of the hairs in one direction depolarizes them and bending them in the opposite direction hyperpolarizing them

31
Q

What creates a rigid unit in the organ of Corti

A

Outer ends of hair cells are tightly attached to reticular lamina, supported by rads of Corti, which are attached to the basilar fibers

32
Q

What do you neurons in the ganglionic of the organ of corti do?

A

The ganglion send axons via the cochlear nerve (CN VIII) into the upper level of the medulla

33
Q

What does movement of the basilar fiber cause movement of?

A

the reticular lamina

34
Q

What does movement of the reticular lamina cause?

A

shearing forces on the hair cells against the tectorial membrane

35
Q

So whenever basilar membrane moves?

A

hair cells become excited

36
Q

What has about 100 sterocilia on the apical border?

A

each hair cell

37
Q

Where are stereocilia longer?

A

on the side farther from the modiolus

38
Q

When cilia are bent in direction of the longer ones??

A

a tensile force is created on the shorter cilia

39
Q

What does the tensile force cause?

A

A mechanical transduction that opens 200 to 300 potassium channels resulting in a depolarization of the hair cell membrane

40
Q

What is the scala media filled with?

A

endolymph

41
Q

What are the scala vestibuli and scala tympani filled with?

A

perilymph

42
Q

What does endolymph contain?

A

a high concentration of potassium and a low concentration of Na (opposite that of the perilymph)

43
Q

+ 80 mv difference btw endolymph and perilymph (scala media is positive) =

A

endocochlear potential

44
Q

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

A

endolymph

45
Q

What are lower bodies of the hair cells surrounded by?

A

perilymph

46
Q

What is the intracellular potential of hair cells?

A

-70 mv with respect to perilymph -150 mv w respect to endolymph

47
Q

How does nervous system detect sound frequencies?

A

by determining positions along the basilar membrane that are most stimulated

48
Q

Explain how the auditory system determines loudness

A

…

49
Q

what is a decibel

A

…

50
Q

describe the relationships btw frequency and pressure in decbels

A

…

51
Q

how does the frequency range that can be heard change w age?

A

…

52
Q

What are components of the auditory nervous system pathway?

A

spiral organ of corti dorsal and ventral cochlear nuclei superior olivary nucleus lateral lemniscus nucleus medial geniculate nucleus (thalmus) auditory cortex

53
Q

Where does decussation occur btw right and left pathways

A

…

54
Q

what is the relationship btw the auditroy tracts and the RAS

A

?

55
Q

where is the auditory cortex located?

A

..

56
Q

Distinguish btw the primary auditory cortex and the auditory association areas

A

…

57
Q

explain how a person determines the direction from which sound comes

A

…

58
Q

Look at all diagram and pictures of lectures.

A

…

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