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Physiology > Exam 2: Ch 10 Sensory Physiology > Flashcards

Exam 2: Ch 10 Sensory Physiology Flashcards

1
Q

 Sensory receptors transduce (=change) environmental information into

A

APs – the common language of NS

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2
Q

 Each type of sensory receptor responds

A

a particular modality (=form of info, e.g. sound, light, pressure)

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3
Q

 Different modalities are perceived as different because

A

because of CNS pathways they stimulate

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4
Q

 2 classification schemes for sensory receptors

A

 1. Structural

 2. Functional

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5
Q

 1. Structural

A

 simple dendritic endings of neurons
• Free (pain, temperature)
• Encapsulated within non-neural structures (pressure) or modified epithelia (taste)

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6
Q

 2. Functional

A

Functional classification of sensory receptors groups them according to type of stimulus they transduce

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7
Q

Functional classification of sensory

A
  • chemoreceptors
  • photoreceptors
  • thermoreceptors
  • mechanoreceptors
  • nociceptors
  • proprioceptors
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8
Q

Chemoreceptors

A

sense chemical stimuli (taste buds, olfactory receptors)

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9
Q

 Photoreceptors

A

transduce light (rods and cones)

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10
Q

 Thermoreceptors

A

respond to temperature changes (heat and cold)

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11
Q

 Mechanoreceptors

A

respond to deformation of their cell membrane (touch, pressure, hair cells of inner ear)

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12
Q

 Nociceptors

A

respond to intense stimuli by signaling pain

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13
Q

 Proprioceptors

A

signal positional information of body parts (joint receptors, golgi tendons, muscle spindles)

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14
Q

 Sensory receptors can also be categorized according to location:

A
  •  Cutaneous receptors

-  Special sense receptors

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15
Q

 Cutaneous receptors

A

are near an epithelial surface (respond to touch, pressure, temperature or pain)

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16
Q

 Special sense receptors

A

are part of a sensory organ (hearing, sight, equilibrium)

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17
Q

 Sensory Receptor Responses

A

 Tonic receptors

 Phasic receptors

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18
Q

 Tonic receptors

A

respond at constant rate as long as stimulus is applied (e.g. pain)

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19
Q

 Phasic receptors

A

respond with burst of activity but quickly reduce firing rate to constant stimulation

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20
Q

Which sensory receptor is  Responsible for sensory adaptation

A

Phasic receptors

- • e.g. smell and touch

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21
Q

 Generator (receptor) potentials

A

sensory receptor equivalents of EPSPs

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22
Q

 Generator (receptor) potentials is produced why

A

in response to adequate stimulus

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23
Q

Generator (receptor) potentials are proportional to

A

stimulus intensity

• NOTE: After threshold is reached, intensity is coded for by AP frequency

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24
Q

In phasic receptors the generator potential

A

adapts to a constant stimulus & quickly diminishes in amplitude

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25
Q

 In tonic receptors, generator potential

A

does not adapt to a constant stimulus

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26
Q

 Cutaneous sensations include the following

A
  • touch
  • pressure
  • heat
  • cold
  • pain
  • ruffini endings & merkel’s discs
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27
Q

Cutaneous sensations are mediated by

A

free & encapsulated nerve endings

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28
Q

heat

A

mediated by free nerve endings; located deeper in dermis

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29
Q

heat elicits pain thru

A

capsaicin receptors; capsaicin is “hot” chemical in chili peppers

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30
Q

cold

A

mediated by free nerve endings; located in upper dermis

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31
Q

pain

A
  • mediated by free nerve endings called nociceptors

• Use glutamate & substance P as NTs; substance P called “pain NT”

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32
Q

 Ruffini endings & Merkel’s discs

A

are slow-adapting, expanded free nerve endings that mediate touch

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33
Q

 Encapsulated nerve endings

A
  • mediate touch, pressure

- adapt quickly and include Meisner’s & Pacinian corpuscles

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34
Q

Two-point touch threshold

A

 Is minimum distance at which 2 points of touch can be perceived as separate

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35
Q

 Two-Point Touch Threshold Measure of

A

of tactile acuity or distance between receptive fields (area of skin whose stimulation results in changes in the firing rate of a neuron)

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36
Q

 Lateral Inhibition

A

 Is CNS process that sharpens sensation

 Sensory neurons at center of stimulation area inhibit more lateral neurons

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37
Q

Lateral Inhibition eg.

A
  • when blunt object touches skin sensory neurons in center are stimulated more than outer ones & inhibit them
  •  Object perceived as single touch with well-defined borders
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38
Q

Taste and smell receptors are

A

are exteroceptors because respond to chemicals in external environment

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39
Q

 Interoceptors

A

respond to chemicals in internal environment

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40
Q

 Taste/Gustation Detects

A

sweet, sour, salty, bitter, & amino acids (umami)

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41
Q

 Taste receptor cells are

A

modified epithelial cells

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42
Q

How many taste receptors in each taste bud?

A

 50-100 are in each taste bud

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43
Q

 Salty & sour

A

do not have receptors

 act by passing through channels

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44
Q

 Sweet & bitter

A
  • have receptors

- act thru G-proteins

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45
Q

 Smell (olfaction) receptors

A

located in olfactory epithelium at top of nasal cavity

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46
Q

 Olfactory apparatus consists of

A

receptor cells, supporting cells, & basal cells

47
Q

Receptor cells of olfactory apparatus are

A

are bipolar neurons that send axons to olfactory bulb

48
Q

Basal cells of olfactory apparatus are

A

are stem cells that produce new receptor cells every 1-2 months

49
Q

supporting cells of olfactory apparatus

A

contain detoxifying enzymes

50
Q

 Odor molecules bind to

A

receptors & act through G-proteins

51
Q

 Ears & Hearing; Vestibular Apparatus

A

provides sense of equilibrium orientation to gravity

52
Q

inner ear

A

 Vestibular apparatus & cochlea

53
Q

 Vestibular apparatus consists of

A

 otolith organs (utricle & saccule)

 semicircular canals

54
Q

Sensory structures of the vestibular apparatus are located with in

A

membranous labyrinth

55
Q

membranous labyrinth is filled with

A

endolymph = fluid similar to intracellular fluid

56
Q

membranous labyrinth is located within

A

bony labyrinth

57
Q

 Utricle and saccule provide

A

info about linear acceleration

58
Q

linear acceleration

A

changes in velocity (acceleration and deceleration) when moving horizontally or vertically)

59
Q

Semicircular canals,

A
  • oriented in 3 planes,

- give sense of angular (rotational) acceleration

60
Q

 Vestibular Apparatus

- Hair cells

A
  • modified epithelial cells
     are receptors for hearing and equilibrium
     each contains 20-50 hair-like extensions called stereocilia
61
Q

stereocilia

A
  • processes with filaments of protein

* 1 of these extentions (longer one) = kinocilium (cilia)

62
Q

 When stereocilia are bent toward kinocilium,

A

hair cell depolarizes & releases NT that stimulates CN VIII

63
Q

 When stereocilia are bent in the opposite direction

A
  • hair cell hyperpolarizes
     In this way, frequency of APs in hair cells carries information about movements that cause the hair cell processes to move
64
Q

 Otolith organs

A

Utricle & Saccule

65
Q

 Utricle and saccule

A
  • each have a macula
     patch of specialized epithelium containing hair and support cells
     Hair cell extensions are embedded in gelatinous otolithic membrane
66
Q

gelatinous otolithic membrane

A

contains calcium carbonate crystals (=otoliths) that resist change in movement

67
Q

Utricle =

A

 sensitive to horizontal acceleration

 Hairs pushed backward during forward acceleration

68
Q

Saccule

A

 sensitive to vertical acceleration

 Hairs pushed upward when person descends

69
Q

Semicircular canals

A

= provide information about rotational acceleration
 project in 3 different planes
 each contains a semicircular duct

70
Q

At base of Semicircular canals

A

is crista ampullaris where sensory hair cells are located

71
Q

 Hair cell processes are embedded in

A

gelatenous membrane = cupula of crista ampullaris with higher density than endolymph

72
Q

when endolymph moves

A

cupula moves and sensory processes bend in opposite direction of angular acceleration

73
Q

 Vestibular nystagmus

A

involuntary oscillations of eyes
 occurs when spinning person stops
 eyes continue to move in direction opposite to spin, then jerk rapidly back to midline

74
Q

Vertigo

A

 is loss of equilibrium

75
Q

Vertigo

 natural response of vestibular apparatus or pathological may be caused by

A

anything that alters firing rate of CN VIII

 Ex: often caused by viral infection

76
Q

 Outer Ear

 Sound waves funneled by

A

by pinna (auricle) into external auditory meatus

77
Q

External auditory meatus

A

channels sound waves to tympanic membrane

78
Q

 Middle ear

A

between tympanic membrane & cochlea; holds ossicles

79
Q

 Malleus (

A

hammer) is attached to tympanic membrane; carries vibrations to incus (anvil)

80
Q

Stapes

A

(stirrup) receives vibrations from incus, transmits to oval window (cochlear membrane)

81
Q

 Stapedius muscle

A

attached to stapes
 provides protection from loud noises
• can contract to dampen large vibrations to prevent nerve damage in cochlea
ear membrane)

82
Q

 Organ of Corti

A

where sound is transduced

83
Q

 Sensory hair cells located on

A

the basilar membrane have projections (steriocilia) projecting into cochlear duct

84
Q

1 row of inner cells extend length of basilar membrane & multiple rows of outer hair cells are embedded in

A

tectorial membrane, which overhangs hair cells with cochlear duct

85
Q

• Pressure waves moving thru cochlear duct create

A

shearing forces between basilar & tectorial membranes, moving & bending stereocilia
• Causing ion channels to open, depolarizing hair cells
• The greater the displacement, the greater the amount of NT released & APs produced

86
Q

 Conduction deafness

A

occurs when transmission of sound waves to oval window is impaired
 helped by hearing aids

87
Q

 Sensorineural (perceptive) deafness

A

is impaired transmission of nerve impulses
 often impacts some pitches more than others
• helped by cochlear implants, which stimulate fibers of CN VIII in response to sounds

88
Q

 Sclera

A

(white of eyes) is outermost layer

89
Q

 Transparent cornea

A

continuous with sclera

90
Q

 light passes thru

A

cornea into anterior chamber, then thru pupil which is formed by the pigmented muscle = iris (controls size of pupil), then thru lens & vitreous to retina

91
Q

• Iris

A

(a pigmented muscle) controls size of pupil

92
Q

• Pupil constricts by

A

contraction of circular muscles

• Under parasympathetic control

93
Q

• Pupil dilation is

A

via contraction of radial muscles

94
Q

 Structure of Eye

A

 Photoreceptors are in retina

 Retina absorbs some light, the rest is absorbed by dark choroid layer

95
Q

Axons of retinal neurons gather at

A

optic disc (blind spot) & exit eye in optic nerve

96
Q

 Visual field

A

part of the external world projected onto retina

97
Q

 Cornea and lens focus the

A

right part of the visual field to the left half of the retina and the left part of the visual field to the right half of the retina

98
Q

 Visual acuity

A

sharpness of vision

99
Q

visual acuity  Depends upon

A

resolving power: ability to distinguish (resolve) 2 closely spaced dots

100
Q

With myopia (nearsightedness) image

A

focused behind retina because eyeball too short; object will have to be further away to be seen

101
Q

 With astigmatism

A

cornea or lens is not symmetrical; light is bent (refracting) unevenly, causing uneven focus

102
Q

 Retina = a multilayered epithelium consisting of

A

 Neurons
 pigmented epithelium
 photoreceptors (rods & cones)

103
Q

 photoreceptors (rods & cones)

A

• neural layers are extension of brain; light must pass through several neural layers before striking rods & cones

104
Q

 Rods & cones face away from

A

from pupil; send sensory info to bipolar cells

105
Q

 Bipolars send electrical activity to

A

ganglion cells

106
Q

 Ganglion cells project axons

A

thru optic nerve to brain

107
Q

 Horizontal cells & amacrine cells are

A

interneurons involved in visual processing in retina

108
Q

 Electrical Activity of Retinal Cells

A

 Ganglion & amacrine cells produce APs

 Rods, cones, bipolar, & horizontal cells produce graded potential changes

109
Q

 Visual transduction is

A

inverse of other sensory systems

110
Q

 In dark, photoreceptors release

A

inhibitory NT that hyperpolarizes bipolars

• Inhibited bipolars do not release excitatory NT onto ganglion cells

111
Q

Light inhibits photoreceptors from

A

releasing inhibitory NT, thus stimulating bipolars, which excite ganglionic cells, which transmit AP to brain

112
Q

 Rods & cones contain

A

many Na+ channels that are open in dark

 This depolarizing Na+ influx is the dark current

113
Q

 Light hyperpolarizes by

A

by closing Na+ channels

• cGMP keeps Na+ channels open; light converts cGMP to GMP & Na+ channels close

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