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Physiology > L22,23 Sound T > Flashcards

L22,23 Sound T Flashcards

1
Q

Function of Auricle (Pinna)?

A

Gathers sound waves
Amplifies sound

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2
Q

Function External Auditory Canal?

A

-Allows air to warm before reaching TM
-Isolates TM from physical damage

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3
Q

Function Tympanic Membrane?

A

-boundary between outer and middle ear
-Vibrates in response to sound
-Changes acoustical energy into mechanical energy.

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4
Q

conduct sound from the tympanic membrane through
the middle ear to the cochlea (the inner ear) is???

A

Ossicles

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5
Q

Attached to the tympanic membrane is ???

A

the handle of the malleus

note*
Malleus bound to the incus by minute ligaments, so
that whenever the malleus moves, the incus moves with it.

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6
Q

Faceplate of the………………. lies against membranous labyrinth of cholea in ( oval window )?

A

stapes

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7
Q

tympanic membrane tensed by?

A

Tensor tympani
لازم يكون مشدود عشان الصوت ينتقل للعظمات الثلاث لان لو كان مرتخي this wouldn’t occur

(tip end of the handle of the malleus is attached to the center of the tympanic membrane and this point of attachment pulled by this muscle ) للتوضيح فقط

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8
Q

articulation of the incus with the stapes causes the
stapes to:

A

1-push forward on the oval and on the cochlear fluid on the other side of window every time the tympanic membrane moves inward

2-pull backward on the fluid every time the malleus moves outward

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9
Q

Sound travels through the ear

A

1- Acoustic energy in the form of sound waves, is channeled into the ear canal by the pinna

2- Sound waves hit the tympanic membrane and cause it to vibrate, drum, changing it into mechanical energy

3- malleus which is attached to the tympanic membrane, starts the ossicles into motion.

4- stapes moves in and out of the oval window of the cochlea creating a fluid motion or hydraulic energy.

5- The fluid movement causes membranes in the Organ of Corti to shear against the hair cells.

6-This creates an electrical signal which is sent up the Auditory Nerve to the brain.
( The brain interpretes it as sound )

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10
Q

Functions of middle ear :

A

1- impedance matching
2-attenuation
3- phase differential effect
4- muscles serve for protection

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11
Q

the ratio of the pressure to the volume displacement at a
given surface in a sound- transmitting medium called?

A

“Impedance”

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12
Q

tympanic membrane and ossicular system provide ………………………between the sound waves in air and the sound vibrations in the fluid of the cochlea:

A

impedance matching

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13
Q

Impedance Efficiency:

A
  • Middle ear converts low pressure high displacement movements of the ear drum
    into high pressure low displacement movements needed for the cochlear fluid movement.
  • 50% of sound energy from TM gets transmitted and absorbed in the cochlea.
  • Without middle ear only 1% of sound energy will be absorbed by the cochlea.
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14
Q

Preferential pathway due to?

A

Ossicular chain

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15
Q

Acoustic separation of windows archived by?

A

1-Intact tympanic membrane and
2-cushion of air around round window

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16
Q

IMPEDANCE MATCHING BY EAR OSSICLES BY 3 MECHANISMS

A

HYDROLIC ACTION OF TYMPANIC MEMBRANE +26dB
LEVER ACTION OF VESICLES 2dB
CURVED MEMBRANE EFFECT +6dB

( all increase sound pressure 22 folds)

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17
Q

HYDROLIC ACTION OF TYMPANIC MEMBRANE

A

-Effective vibratory area of tympanic membrane (55mm2)
is more than stapes oval window surface area(3.2mm2’
-So force produced by sound concentrated over small area
-Amplifying Pressure on Oval window

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18
Q

LEVER ACTION OF VESICLES?

A

-Handle of Malleus 1.3 times longer than Long process of Incus, providing Mechanical Leverage Advantage.
So Ossicles increases force of movement by 1.3 times

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19
Q

CURVED MEMBRANE EFFECT?

A

Movement of Tympanic membrane more at Periphery than at Center where Malleus is attached. So provide some leverage

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20
Q

Reduces sound pressure amplitude by Changing mobility & Transmission properties of Ear ossicles called?

A

ATTENUATION REFLEX (Tympanic reflex/Acoustic reflex)

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21
Q

When a loud sound is transmitted what happen?

A

stapedius muscle contracts and to a lesser extent, the tensor tympani contracts, reduce dB by 30-40

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22
Q

Responsible for attenuation ?

A

Stapedius, tensor tympani muscles

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23
Q

Tensor Tympani - pull Malleus………………
Stapedius - pulls stapes………………….

A

inwards
outwards

-Both makes Ossicular system rigid & no vibrations.
-Sound intensity Decreased by 30-40 db.

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24
Q

Function of the attenuation reflex

A


1. To protect the cochlea from damaging vibrations
2-Mask low frequency sounds in loud environments
3-decrease a person’s hearing sensitivity to his speech

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25
Q

Three Parts of Labyrinths:

A

1. Cochlea ( hearing )
2. Semicircular canals ( sense of equilibrium)
3. Vestibule ( in equilibrium & hearing)

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26
Q

Exit from inner ear is?

A

Round window

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27
Q

Entrance to inner ear is ?

A

Oval window

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28
Q

Sensory organ for sound transduction ?

A

Organ of corti

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29
Q

cochlea consists of three tubes
coiled side by side:

A

(1) the scala vestibuli,
(2) the scala media
(3) the scala tympani.

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30
Q

-Reissner’s membrane (vestibular membrane):
Between?

A

The scala vestibuli and scala media

31
Q

-Basilar membrane: Between?

A

the scala tympani and scala media

32
Q

attached along one edge of the wall of Scala media

A

-Tectorial membrane:

33
Q

Organ of corti located in ?

A

Scala media on top of basilar membrane

34
Q

Organ of corti contain ?

A

series of electromechanically sensitive cells hair cells

35
Q

They are the receptive end organs that generate nerve impulses?

A

hair cells of organ of corti

36
Q

Importance of Reissner’s membrane ?

A

Maintain a special kind of fluid in the scala media that is required for Sound-receptive hair cells

37
Q

Sound vibrations enter the scala vestibuli from the ?

A

faceplate of the stapes at the oval window.

38
Q

faceplate of stapes covers oval window and is connected with the window’s edges by ?

A

a loose annular ligament so that it can move inward and outward with the sound vibrations.

39
Q

• Inward movement causes the fluid to move ?

A

move forward in the scala vestibuli and scala media,

40
Q

• outward movement causes the fluid to move?

A

backward

41
Q

Movements of the hair cells in contact with the tectorial membrane led to?

A

transduce mechanical vibrations into electrical signals which generate nerve impulses along cochlear branch of CN VIII

42
Q

Scala vestibule and scala tympani connects to each other
at?

A

the apex of cochlea - Helicotrema

43
Q

The basilar fibers project from ?

A

Modiolus fo cochlea

44
Q

Basilar fibers

A

Stiff, elastic, reed-like
Fixed at their basal ends
Free at distal end (embeddedin basal membrane)

45
Q

The lengths of the basilar fibers………….. beginning at the oval window and going from the base of the cochlea to the apex

A

increase progressively

(from a length of about 0.04mm near the oval and round windows to 0.5 mm at the tip of the cochlea (the “helicotrema”), a 12- fold increase in length)
* يعني اطول شيء له عند helicotrema

46
Q

The diametersof the basilar fibers,………… from the oval window to the helicotrema

A

decrease

(so that their overall stiffness decreases more than
100-fold)

47
Q

high-frequency sound wave travels…………..

A

only a short distance along the basilar membrane before it reaches its resonant point and dies ( base )

48
Q

medium-frequency sound wave travels about…………..

A

halfwayand then dies ( middle )

49
Q

very low frequency sound wave travels…………

A

the entire distance along the Basilar membrane ( apex )

50
Q

features of the traveling wave ?

A

1-it travels fast along the initial portion of the basilar membrane but becomes progressively slower as it goes farther into the cochlea.

2-Each wave is relatively weak at the outset but becomes strong when it reaches that portion of the basilar membrane that has a natural resonant frequency

3-((different patterns of transmission for sound waves of different frequencies))

51
Q

The organ of Corti function?

A

1-is the receptor organ that generates nerve impulses in response to vibration of the basilar membrane

2- nerve fibers that stimulated led to spiral ganglion which sends axons to cochlear nerve

} Note
(organ of Corti lies on the surface of the basilar fibers and basilar membrane )

52
Q

sensory receptors in the organ of Corti are?

A

hair cells: ( with many steriocilia & 1 kinocilium )
“inner” hair cells:
Single row
Large diameter
Less numbers
90% of afferent synapse on it
special importance for the detection of sound اهم من الثانيه

“outer” hair cells:
three or four rows
Small diameter
More numbers
Control the sensitivity of inner cells

53
Q

The bases and sides of the hair cells
synapse with?

A

a network of cochlea nerve endings

54
Q

spiral ganglion of Corti, which lies in the?

A

modiolus (center) of the cochlea.

55
Q

-spiral ganglion send axons into the cochlear nerve and
then into the central nervous system at the level of?

A

upper medulla

56
Q

Afferent fibers of cochlear nerve coils in?

A

Bases of hair cell

57
Q

stereocilia, project upward from the hair cells and
either?

A

touch or are embedded in the tectorial membrane

58
Q

lies above the stereoilia in the scala media?

A

tectorial membrane

59
Q

Causes cilia to bend ?

A

Shearing action in the BM and TM

(Deflection of basal membrane caused by passing pressure )

60
Q

mechanically* gated channels open via?

A

Pull of Tiplinks

Then>
Inward current causes graded potential and release of:
Glutamate from hair cell onto sensory neuron

61
Q

Bending of the hairs in one direction led to ?

A

Depolarization in the hair cells

(( bending in the opposite direction hyperpolarizes them))

62
Q

The outer ends of the haircells are fixed tightly in a rigid structure composed of a flat plate, called?

A

reticular lamina

((supported by triangular rods of Corti, which are
attached tightly to the basilar fibers ))

63
Q

move as a rigid unit:

A

The basilar fibers,
the rods of Corti, and
the reticular lamina

64
Q

Excitation of hair cells:

A

} Upward movement of the basilar fiber rocks the reticular lamina upward and inward toward the modiolus

} Then, when the basilar membrane moves downward the reticular lamina rocks downward and outward

} The inward and outward motion causes the hairs on the hair cells to shear back and forth against the tectorial membrane

} Thus, the hair cells are excited whenever the basilar membrane vibrates.

65
Q

Auditory signals are transmitted mainly by :

A

Inner hair cell

But, if the outer cells are damaged while the inner cells remain fully functional a
large amount of hearing loss occurs.

((outer hair cells in control the sensitivity of the inner hair cells at different sound pitches, a phenomenon called “tuning” of the receptor system**))

66
Q

Stereocilia characters :

A

-stereocilia become progressively longer on the side of the hair cell away from the modiolus,

  • the tops of the shorter stereocilia are attached by thin filaments to the back sides of their adjacent longer stereocilia.

——-whenever the cilia are bent in the direction of the longer ones, the tips of the smaller stereocilia are tugged outward from the surface of the hair cell———

67
Q

Hair cell receptor potential:

A

-mechanical transduction
-cation-conducting channels opened

  • rapid movement of K+ from surrounding scala media fluid into the stereocilia, which causes:
    depolarization of the hair cell membrane.

> when the basilar fibers bend toward the scala vestibuli the hair cells
depolarize and in the opposite direction ( to tympani ) they hyperpolarize, thereby:
(generating an alternating hair cell receptor potential)

> stimulates the cochlear nerve endings that synapse with the bases of the hair cells.

> Release glutamate

68
Q

Stereocilia coupled by?

A

“tip links”

69
Q

Sensory transduction in hair cell
Upward displacement of basilar membrane led to ?

A

1-bends stereocilia towards kinocillium
2-Opens mechanically gated non-selective cation channels = depolarization
3-Excitatory NT released = AP in afferent nerve fibre
-K+ entry electrotonically depolarises the cell
-VGCC opens - Ca2+ influx
-Ca2+ modulates synaptic neurotransmitter release
-Opens Kca channels for Ke efflux
-Ca2+ influx ad Ca2+ induced K+ efflux > electrical resonance and tuning of hair cell

(Not all afferent fibres fire AP in response to particular sound)

70
Q

• Detection of Changes in Loudness

A

-As sound becomes louder > amplitude increases >
excite the nerve endings more rapid rates

> more and more hair causing (spatial summation of impulses)

> Outer hair cells do not become stimulate until the vibration of the basilar
membrane
reaches high intensity

((The Power Law- a person interprets changes in intensity in proportion to an inverse power of the function of the actual intensity تخبيص محدد مع تحريم))

71
Q

• Determination of Sound Frequency:

A

The “Place” Principle- major method to detect different sound frequencies is to determine the position along the basilar membrane that is most stimulated

72
Q

Sensory pathway for hearing

A

اختصار:
( hair cell > spiral ganglion > cochlear n > SON > LL> IC> MGB > auditory radiation > auditory cortex )

تفاصيله:
1- Hair cells stimulated

2- Sensory neuron axons (cell bodies in spiral ganglion) make up cochlear branch of vestibulocochlear nerve (VIII)

3- Sensory neuron axons synapse onto neurons in cochlear nucleus (upper medulla) At this point, all the fibers synapse, and second-order neurons pass mainly to the opposite side of the brain stem to terminate in the superior olivary nucleus And then passes upward through the lateral lemniscus

4- Information ascends bilaterally (synapsing on the way) to inferior colliculus (midbrain)

5-Inferior colliculus neurons synapse at medial geniculate nucleus (thalamus)

6- Projection fibers from thalamus reach primary auditory cortex (superior temporal gyrus)

73
Q

Function of the Cerebral Cortex in Hearing

A
  • Sound frequency perception
  • Discrimination of sound patterns
  • Determination of direction from which sound comes
74
Q

Medial and lateral superior olive (MSO and LSO) important in ?

A

computing location of sound

Physiology (9 decks)

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