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Neuroanatomy > Vestibular and Auditory (2) > Flashcards

Vestibular and Auditory (2) Flashcards

1
Q

A complex sound can be decomposed into what? How is it perceived?

A

spectrum of pure tones, each of a different frequency, no dominant rhythmicity get perceived as noise, hisses, or scratches; it is a pitch when there is a dominant rhythmicity

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2
Q

What is the measure of sound intensity?

A

decibel

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3
Q

What conduction properties and medium results in low impedence?

A

air, sound waves have low pressures and cause large

displacements of air molecules

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4
Q

What conduction properties and medium results in high impedence?

A

water, sound waves have high pressures and cause

small displacements of molecules

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5
Q

Mismatch in impedance causes what?

A

reflection of sound at an interface

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6
Q

What is necessary in order for the sound waves traveling through air to pass into the fluid of the cochlea?

A

pressure on the oval window must be greater than the pressure on the tympanic membrane; need ossicles to amplify

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7
Q

Increasing the force on the membrane is achieved how?

A

arm of malleus to which tympanic membrane is attached is longer than arm of the incus to which the stapes is attached-> lever action-> slight amplification of the sound pressure

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8
Q

Reducing the surface area of the membrane is achieved how?

A

surface area of oval window less than tympanic membrane; same force exerted on both-> smaller receives greater pressure

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9
Q

The middle ear does what to the sound force at the

oval window ? air molecule displacement?

A

magnifies 1.5 times; reduces 1.5 times

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10
Q

Mechanical control of ear sensitivity is regulated

by what?

A

tensor tympani and stapedius muscles; Contraction reduces sound transmission by 20 db; Ossicle joints could otherwise separate causing distortion of the sound

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11
Q

What is the attenuation reflex?

A

tensor tympani and stapedius muscles contract reflexively at loud sounds to protect the auditory
apparatus; delay of 50-100 msec

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12
Q

The basilar membrane dies what toward the apex?

A

widens

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13
Q

What is the helicotrema?

A

hole at the apex of the basilar membrane, connects the scala vestibuli and scala tympani

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14
Q

Why does the basilar membrane holding the hair cells vibrates easily at sound frequencies?

A

partly-coiling of cochlea; mainly- membrane structure varying width along length; stiffness of membrane decreases from base to apex;

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15
Q

The tectorial membrane has what function? characteristics?

A

filter of auditory system; holds tips of hairs, very flexible attachment, considerable mass, bends freely w/ slow movements, very stiff w/ fast movements (at sound frequencies); mechanical arrangement provides magnification of hair movement ->increases sensitivity

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16
Q

Bending of the stereocilia in cochlea is produced by what?

A

upward motion of the basilar membrane

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17
Q

Transduction by Hair Cells is acheived how?

A

hair tip toward tallest, cap over ion channel lifts, K+ into hair cell ->depolarization (endolymph high K+.); activates voltage-gated Ca2+ channels, Ca2+ triggers release of NT-> activates spiral ganglion fibers

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18
Q

Outer hair cells respond to sound with what?

A

receptor potential & change in length, Depol.-> motor proteins (prestin) contract-> cell shrinks in length->may augment basilar-memb. motion-> cochlear amplifier

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19
Q

Coding of sound intensity is done in what two interrelated ways?

A

Rate: intensity increases-> discharge rate of individual hair cell afferents increases; Recruitment: intensity increases, additional receptors get recruited. Not all
receptors have the same threshold.

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20
Q

What is Place theory of pitch coding?

A

hair cell measures energy in narrow band of frequencies; vibration pattern of basilar memb.& tonotopic arrang. of hair cells along membrane sharpens response of hair, arrang. provides CNS w/ frequency spectrum of sound

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21
Q

What is characteristic frequency?

A

An auditory neuron is most responsive to one frequency

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22
Q

What is Tonotopy?

A

systematic organization within auditory structure based on characteristic frequency; basilar membrane, auditory nerve, and cochlear nucleus

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23
Q

What is duplex theory of sound localization?

A

Localization of sound in horizontal plane; relies on Interaural time delay in short sound; continuous sound needs interaural intensity difference

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24
Q

Localization of sound in the vertical plane is based on reflection from where?

A

pinna

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25
Q

The vestibular sensory organs are the primary

organs of what?

A

equilibrium; transduce forces associated with head acceleration and gravity into a biological signal

26
Q

The vestibular apparatus in humans serves what three major functions?

A

perception of orientation, posture, eye movemnets

27
Q

The vestibular apparatus is what?

A

labyrinth of fluid filled canals and cavities in the temporal bone; associated with the cochlea.

28
Q

Angular accelerations are detected by what?

A

3 semicircular canals, horizontal, superior & posterior

29
Q

What is the ampulla? ampullary crest?

A

swelling on each semicircular canal; contains sensory epithelia

30
Q

Sensory epithelium of vestibular system consists of what?

A

vestibular hair cells-> w/ cilia embedded in cupula

31
Q

The canals/cavities in vestibular labyrinth are surrounded by the what? and contain?

A

fluid, perilymph; the fluid, endolymph

32
Q

What are the properties of endolymph?

A

high K+, low Na+; formed by stria vascularis; found in scala media; similar to cytoplasm; potential of +80 mV.

33
Q

What are the properties of perilymph?

A

high Na+, low K+; similar to CSF, communicates w/ CSF; in scala tympani & scala vestibule; similar to most ECF in body (0 mV).

34
Q

What are the characteristics of vestiburlar hair cells?

A

stereocilia on apical surface-gives the hair cell a morphological axis of polarity; have a kinocilium.

35
Q

The membranous labyrinth contains what?

A 
auditory structures (cochlear duct), vestibular structures
(utricle, saccule and semicircular ducts).
36
Q

Vestibular afferents fire how? why?

A

tonically (sustained)- some cells firing persists indefinitely, info about sustained stimulation (gravity) phasically (short bursts) some cells adapt to continued
stimulation-> info about abrupt changes in bodily
accelerations

37
Q

Vestibular efferents send information from where to where? Why?

A

brainstem back to hair cells; Stimulation decreases excitability of some hair cells (IPSP); Activation of some efferent fibers may increase excitability of some hair cells

38
Q

When the stereocilia are bent toward the kinocilium what happens?

A

conductance of apical membrane increases for cations,

depolarization-> more transmitter is released

39
Q

When the stereocilia are bent away from the kinocilium what happens?

A

hair cell is hyperpolarized; less transmitter is released.

40
Q

When patterns of motion are such that the endolymph

moves with respect to the wall of the canals there will be what?

A

excitation in the member of a pair of canals on one side of the head and inhibition on the other side

41
Q

Rotation of the body to the left will cause bending of the

cilia in the left horizontal canal toward what? Causing?

A

utricle =excitation; horizontal canal on the right side will be inhibited as its cilia are bent away from the utricle

42
Q

How do the superior and posterior canals pair as they work?

A

superior canal on one side and posterior canal on the

other side work as a pair

43
Q

Linear accelerations or head tilt are detected by what?

A

two otolith organs;

44
Q

The utricle is connected to what?

A

all semicircular canals

45
Q

The saccule is connected to what?

A

cochlea

46
Q

Sensory epithelia within otolith organs are called what?

A

macula utriculi and macula sacculi

47
Q

The otolithic membrane is what?

A

gelatinous mass containing otoconia, stones of calcium carbonate crystals (calcite).

48
Q

what is the function of the otoconia?

A

increase the specific gravity of the otolithic membrane to about twice that of the endolymph; direction of bending cilia depends on orientation of resultant acceleration force

49
Q

What is the characteristic of the orientation of the vestibular hair cells?

A

hair cells of utricular macula do not all have the same orientation with respect to kinocilia. may be bent even though the head is maintained stationary.

50
Q

Vestibulo-ocular reflexes do what?

A

compensate head movement; head moves, eyes are kept still; Visual cues not necessary

51
Q

Vestibular nystagmus does what?

A

resets eye position during sustained rotation of the head.

52
Q

Otolith reflexes do what? What are they?

A

compensate for linear motion and head deviations relative to gravity; Translational vestibulo-ocular reflex and Ocular counter-rolling response

53
Q

Translational vestibulo-ocular reflex does what?

A

compensates linear head movement; input from otoliths; Graded modification of eye movement-> focus on near objects versus distant objects as one is moving in a linear direction as in a moving car.

54
Q

Ocular counter-rolling response does what?

A

compensates for head tilt in vertical; input from otoliths; head tilts out of vertical position, otolith organs estimate deviation from vertical and initiate counter-rolling response of eyes to compensate.

55
Q

The optokinetic system supplements what?

A

vestibuloocular reflexes; makes up for Habituation and Insensitivity to slow head movements

56
Q

Habituation is what?

A

reduction in responses by semicircular canals with prolonged rotation

57
Q

Insensitivity to slow head movements results from what?

A

Slow rotation of head won’t move endolymph;

58
Q

The optokinetic reflex works how?

A

as eyes move fixed objects seem to move opposite direction as head; drives eyes in direction of image motion; complements vestibulo-ocular reflex; responds to very slow visual image motion, can take over as vestibular signal decays

59
Q

Utricle and saccule maculae detect what?

A

linear acceleration

60
Q

Meniere’s disease is what? cause?

A

idiopathicendolymphatic hydrops; disorder of semicircular canals and cochlea, recurrent attacks of dizziness, tinnitus (ringing in
the ear) distorted hearing; unknown cause; appears attacks ensue from poor drainage of endolymph

Neuroanatomy (17 decks)

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