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PHYSL 214 > Special Senses > Flashcards

Special Senses Flashcards

1
Q

what is an adequate stimulus?

A

energy that sensory endings respond to

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2
Q

what must an adequate stimulus be converted to?

A

electrochemical energy (AP or ∆Vm)

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3
Q

what is the conversion of an adequate stimulus to electrochemical energy called?

A

primary transduction process

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4
Q

what is the primary transduction process for vision and hearing?

A

vision: photon into APs
hearing: pressure waves into APs

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5
Q

what is a generator potential?

A

a non-propagated, graded potential, usually depolarizing (~EPSB)

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6
Q

what is the magnitude of a generator potential proportional to?

A

strength of the stimulus

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7
Q

what wavelengths of light can humans see?

A

390-700nm

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8
Q

approx. how many colours can humans detect?

A

2.3-7.5 million

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9
Q

what is the sclera?

A

tough, white, fibrous part of the eye

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10
Q

what is the cornea?

A

clear bulb in the front of the eye, continuous w/ sclera

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11
Q

what is the conjunctiva?

A

thin, protective membrane that covers the cornea

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12
Q

what is the most important part of the eye for focusing?

A

cornea (more than the lens)

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13
Q

what is the anterior chamber?

A

clear fluid-filled chamber behind cornea and allows it to act as a unit w/ the lens

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14
Q

what is the aqueous humour?

A

clear fluid that fills the anterior and posterior chamber (~water)

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15
Q

what produces vs drains the aqueous humour?

A

ciliary body and canal of Schlemm (back to front of iris)

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16
Q

where is the canal of Schlemm?

A

at the corneal-scleral junction

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17
Q

what is immediately behind the anterior chamber?

A

crystalline lens

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18
Q

what are analogs for the course and fine focus of a microscope?

A

fine: lens
coarse: cornea

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19
Q

what are 2 properties of the crystalline lens?

A

is convex (converges light) and elastic

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20
Q

what is behind the lens?

A

vitreous chamber

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21
Q

what is the vitreous chamber?

A

large chamber filled with gelatinous substance called vitreous (~glass) that inflates the eye

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22
Q

what is at the back of the eye?

A

retina

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23
Q

what is the retina?

A

layers of receptor (rods and cones) and processing (bipolar, amacrine and ganglion) cells

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24
Q

what is behind the retina?

A

choroid layer

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25
Q

what is the choroid layer?

A

layer of black/brown pigment cells called melanin that absorb excess light

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26
Q

what is the process of light passage into the eye? (7)

A

light strikes cornea, is partially focused, passes through anterior chamber and pupil, focused by lens, passes through vitreous chamber, strikes retina, absorbed by receptor and processing cells or pigment cells

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27
Q

what is the pupil?

A

opening of the iris

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28
Q

what is the posterior chamber?

A

clear fluid-filled chamber behind iris

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29
Q

what is the purpose of pigment cells?

A

prevent light scatter which would blur image

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30
Q

what is accomodation?

A

process wherein lens curvature is increased (anterior side most affected)

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31
Q

when does accomodation occur?

A

near-vision

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32
Q

what holds the lens in place behind the iris?

A

suspensory ligaments (aka zonule fibers)

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33
Q

what are suspensory/zonule fibers attached to?

A

sphincter-like muscle called ciliary muscle

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34
Q

what occurs when the ciliary muscle is relaxed vs contracted? what kind of vision does this apply to?

A

relaxed: incr tension in suspensory ligaments and flattens lens (distance-vision)
contracted: decr tension in suspensory ligaments and thickens lens (near-vision)

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35
Q

what is refraction?

A

deflection of light as it passes from one medium to another (difference in velocity)

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36
Q

what is the focal distance?

A

distance from refractive surface (cornea) to point of convergence

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37
Q

what is the diopter? (2)

A

reciprocal of focal distance (m) and focal power of a corrective lens

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38
Q

what is the refractive power of the cornea in diopters?

A

42-43 diopters

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39
Q

what does a value of 42 diopters mean?

A

parallel light is focused 0.024m (distance btwn cornea and retina) behind refractive surface (1/42)

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40
Q

what is myopia? most common cause?

A

nearsightedness; eye is too long and light converges before retina

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41
Q

what is hyperopia? most common cause?

A

farsightedness; eye is too short and light converges behind retina

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42
Q

what is presbyopia? most common cause?

A

decr ability to focus; stiffening of lens w/ age

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43
Q

what is emmetropia?

A

normal vision

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44
Q

what is astigmatism?

A

corneal/lens surface is more curved in one plane than the other (difference in refraction btwn 2 planes)

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45
Q

what does a point of light look like w/ astigmatism?

A

line or an oval

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46
Q

what kind of lens do near vs farsighted eyes require?

A

near: negative/concave (diverges light in front of eye)
far: positive/convex (converges light in front of eye)

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47
Q

what does astigmatism cause?

A

light unfocused at any distance

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48
Q

what lens is used for astigmatism?

A

cylindrical lens

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49
Q

why are cylindrical lenses used for astigmatism?

A

adds lens power in specific meridians of the lens

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50
Q

what does a prescription of -1.00 x -1.25 x 180 correspond to?

A
  • 1.00: nearsighted by 1 diopter (+: far)
  • 1.25: lens power of correction for astigmatism
    180: axis of cylindrical lens power
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51
Q

what the difference btwn a + and - cylindrical lens?

A

+: 1/2 convex (flat on 1 side)

-: 1/2 concave (flat on 1 side)

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52
Q

where do blood vessels enter eye?

A

optic nerve

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53
Q

where is the greatest area of visual acuity?

A

fovea

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54
Q

t/f: while the retina is as transparent as possible, some light is deflected away

A

true

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55
Q

what are the first cells light strikes in the retina but the last in the common pathway?

A

ganglion cells

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56
Q

which cells in the eye conduct APs and send signals to brain?

A

ganglion

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57
Q

what do the outer vs inner segments of receptor cells face?

A

inner: vitreous chamber
outer: pigment cells

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58
Q

how are discs in bottom of outer segment of receptor cells replaced?

A

are shed and phagocytosed by retinal pigment epithelium (RPE)

59
Q

what pigment do discs of receptive cells contain?

A

rhodopsin

60
Q

how many rods vs cones are there per retina?

A

rods; 100-125 million

cones: 6 million

61
Q

which receptor cells detect shades of grey vs colours?

A

rods: shades of grey
cones: colour

62
Q

are rods or cones more sensitive?

A

rods: higher sensitivity
cones: lower sensitivity (require brighter light)

63
Q

do the pathways of rods vs cones have high acuity or low acuity?

A

rods: low acuity (not sharp)
cones: high acuity (high detail)

64
Q

are rods or cones better for night vs day vision?

A

rods: night
cones: day

65
Q

is there little or high convergence (>1/bipolar cell) in retinal pathways for rods vs cones?

A

rods: high convergence
cones: little convergence

66
Q

where are rods vs cones concentrated in retina?

A

rods: periphery
cones: fovea

67
Q

what is the transduction process in the retina when it is dark? (3 cells, 8 steps)

A

receptor cell: high [cGMP], Na channels open, depol., Ca channels open, Glu release (inhibitory NT),
bipolar cells: inhibited,
ganglion cell: no AP, no activation of lateral geniculate nucleus in thalamus

68
Q

what is the transduction process in the retina when it is light? (3 cells, 11 steps)

A

receptor cell: isomerization of retinal w/ light absorption, G protein (transducin) activation, activates phosphodiesterase, breaks down cGMP, Na channels close, hyperpol., Ca channels close, decr release of Glu (inhibitory NT)
bipolar cells: disinhibited (depol.)
ganglion cell: AP, activation of lateral geniculate nucleus in thalamus

69
Q

what is retinal a derivative of?

A

vitamin A (retinal is aldehyde form)

70
Q

what isomerization occurs in the eye w/ light absorption?

A

11-cis retinal to all-trans retinal

71
Q

what is rhodopsin made of? (2)

A

retinal and opsin protein

72
Q

what does the apical side of the RPE face?

A

outer segment of photoreceptors

73
Q

what are 4 functions of the RPE?

A

absorbs some light not absorbed by photoreceptors, transports nutrients/ions to photoreceptors, regenerates 11-cis retinal, daily phagocytosis of photoreceptors (~10%)

74
Q

what occurs after light generates all-trans retinal?

A

trans-retinal (aldehyde) reduced to trans-retinol (alcohol), exits rod cell and transported to RPE cell, converted to 11-cis retinol then to 11-cis retinal and returned to rod cell to rejoin w/ opsin (forms rhodopsin)

75
Q

what is a receptive field?

A

area on retina/region in visual field that activates or inhibits bipolar or ganglion cells when stimulated by light

76
Q

how do cells in the brain signal (other than ganglion cells)?

A

by EPSPs or IBSPs

77
Q

what are 2 ways receptive fields (RF) can be arranged?

A

on-center or off-center

78
Q

what does central vs peripheral stimulation of an on-center RF cause?

A

central: incr APs then decr when stimulus removed
peri: decr APs then incr when stimulus removed

79
Q

what does central vs peripheral stimulation of an off-center RF cause?

A

central: decr APs then incr when stimulus removed
peri: incr APs then decr when stimulus removed

80
Q

how many ganglion cells respond per RF?

A

one

81
Q

what occurs during diffuse (entire) illumination of an RF?

A

continuous firing of APs regardless of on/off-center RF

82
Q

t/f: RFs don’t overlap

A

false, RFs can overlap

83
Q

what occurs when 2 on- or 2 off-center RFs overlap?

A

stimulus will inhibit one ganglion cell and activate the other

84
Q

what occurs when an on-center and off-center RF overlap?

A

stimulus will activate or inhibit both ganglion cells

85
Q

Where do ON vs OFF bipolar cells have their axon terminals?

A

on: inner plexiform layer
off: outer plexiform layer

86
Q

What 2 Glu receptors do OFF bipolar cells express? And why?

A

AMPARs and kianate-type receptors (cation channels); light decr Glu release from photoreceptors (hyperpol.) so cation channels don’t open and bipolar cell hyperpolarizes and ganglion cell doesn’t generate AP

87
Q

What Glu receptor do ON bipolar cells express? And why?

A

mGluR6 (metabotropic) that closes TRPM1 (cation channel); light decr Glu release from photoreceptors (hyperpol.) so cation channels open and bipolar cell depolarizes and ganglion cell generates AP

88
Q

t/f: all optic nerve fibres cross over at the optic chiasma

A

False

89
Q

what range of frequencies can humans hear?

A

20-20 000Hz

90
Q

approx. how many tones can humans distinguish?

A

340 000

91
Q

what is the concha?

A

deepest depression of pinna that helps funnel sound into external auditory meatus (vertical to horizontal)

92
Q

what is the pinna and its function?

A

flaps of skin on outer ear that funnels sounds into external auditory meatus (vertical to horizontal)

93
Q

what is the external auditory meatus?

A

ear canal

94
Q

what is the tympanic memb?

A

ear drum

95
Q

what are the 4 parts of the outer ear?

A

pinna, concha, external auditory meatus, tympanic memb

96
Q

what are the 3 parts of the middle ear?

A

(tympanic memb) malleus, incus and stapes (oval window)

97
Q

what are 3 function of the external ear?

A

protects tympanic memb (internalizes it into ear), funnels sound, gathers sound E

98
Q

what is the issue with the tympanic memb being internalized?

A

dark, moist enviro can promote fungal infections and insects

99
Q

what is cerumen and its funciton?

A

ear wax; anti-bacterial (reduce viability by 99%) and anti-fungal properties

100
Q

what allows the cerumen to be anti-bacterial and fungal? (3)

A

acidic pH (6), saturated fa, and lysozymes

101
Q

what is the purpose of having hair in the external auditory meatus?

A

can detect individual of insects to be removed

102
Q

what are the 2 protective features of the external ear?

A

cerumen and hairs

103
Q

what is the function of the external auditory meatus?

A

gathers sound E (incr by 30-100x) and focuses it on tympanic memb

104
Q

what is the function of the Eustachian tube?

A

connects middle ear with pharynx to balance internal and external Ps on tympanic memb

105
Q

what fills the middle ear?

A

air (not fluid)

106
Q

what is the major function of the middle ear?

A

matches low-impedance airborne sounds to higher impedance sounds in fluid-filled inner ear

107
Q

what is impedance?

A

a medium’s resistance to movement

108
Q

approx. what % of sound E is lost in transition from air to water?

A

99.9% (signals importance of middle ear)

109
Q

what 2 processes in middle ear incr sound E by 200x?

A
  1. decr in diameter from tymp. memb. to oval window (20x)

2. lever action of ossicles (33%)

110
Q

what are the 2 middle ear muscles?

A

tensor tympani and stapedius (more important)

111
Q

what is the tensor tympani muscle connected to?

A

malleus and Eustachian tube

112
Q

what is the stapedius muscle attached to?

A

wall of middle ear and neck of stapes near junction w/ incus

113
Q

what is the purpose of the middle ear muscles?

A

noise reduction (contractions dampen ossicle vibrations)

114
Q

t/f: the middle ear muscles can adapt to very loud, sudden noises

A

false, were not adapted for this

115
Q

what is the main structure of the inner ear?

A

cochlea (snail shell)

116
Q

what are the 3 tubes of the cochlea?

A

scala vestibuli and scala tympani (1 tube-2 parts), scala media (cochlear duct)

117
Q

what joins the scala vestibuli and scala tympani?

A

helicotrema (corner)

118
Q

what separates the scala vestibuli and scala media (cochlear duct)?

A

Reissner’s/vestibular memb

119
Q

what fills the scala vestibuli and scala tympani?

A

perilymph

120
Q

what fills the scala media (cochlear duct)?

A

endolymph

121
Q

what duct funnels from the oval window?

A

scala vestibuli

122
Q

what duct funnels into the round window?

A

scala tympani

123
Q

t/f: the scala media is connected to the scala vestibuli and scala tympani

A

false, scala media is a closed chamber

124
Q

what separates the scala tympani and scala media (cochlear duct)?

A

Basilar memb

125
Q

what is the Basilar memb?

A

memb composed of fibres

126
Q

how do the fibers of the basilar memb change from the oval to round window (apex)?

A

more narrow and stiff to broader and more flexible

127
Q

what is the purpose of having different fibres on the basilar memb?

A

can detect high or low frequency sounds (and signal accordingly)

128
Q

what does the organ of corti rest on?

A

basilar memb (in scala media/cochlear duct)

129
Q

what is the organ of corti composed of?

A

single row of inner and outer hair cells that the tectorial memb rests on

130
Q

what is the functions of the inner vs outer hair cells in organ of corti?

A

inner: sensory (encode sound)
outer: motor (sound f analysis)

131
Q

how are Pwaves in air converted to Pwaves in fluid in ear? (6)

A

sound waves funneled into external auditory meatus and vibrates tympanic memb, ossicles vibrate and stapes pushes on oval window, perilymph is compressed, basilar+Reissner’s memb vibrate, organ of corti moves up and down, hair cells shear against tectorial memb

132
Q

what is shearing?

A

force btwn 2 parts as they slide opposite to each other parallel w/ their plane of contact

133
Q

hair cells have ____________ that align _________ in the front and ________ in the back

A

stereocilia, shortest, tallest

134
Q

what are stereocilia of hair cells attached to?

A

tectorial memb

135
Q

when is a response observed in inner hair cells?

A

when they move in the direction of the tallest stereocilia

136
Q

what is the ion composition of endolymph?

A

high [K+], low [Na+] (V across hair cells is largest in body)

137
Q

what is the ionic composition of perilymph comparable to?

A

plasma and cerebrospinal fluid

138
Q

what occurs in hair cells (to brain) when stereocilia shear toward the tallest one? (5)

A

K-channels open (tip-links), K from endolymph flows into cell and depolarizes it, graded potential changes, rate of APs in auditory nerve changes, stimulation of auditory cortex (temporal lobe)

139
Q

what separates the stereocilia from the body of the hair cell?

A

reticular lamina (body of cell not in endolymph)

140
Q

how do we determine whether a sound is high or low pitched? (process)

A

Pwaves in perilymph propagate from base to apex of basilar memb, growing in A but decr in velocity until it reaches a max. displacement which correlates to its frequency

141
Q

where in the cochlea are high vs low frequency sounds detected and why? (place principle)

A

high f: base; has stiffer, shorter stereocilia

low f: apex; has longer, floppier stereocilia

142
Q

what is the purpose of the round window?

A

dissipates E (no sound perception)

143
Q

what does it mean to say mGluR6 is “sign inverting”?

A

activation of mGluR6 on ON-bipolar cells by Glu (dark) causes CLOSURE of TRPM1 cation channels and thus hyperpolarization of bipolar cell (ganglion not activation)

PHYSL 214 (6 decks)

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