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NEURO 3000 > ch. 12 - somatic sensory system > Flashcards

ch. 12 - somatic sensory system Flashcards

1
Q

somatic sensation

A

enables our body to feel, to ache, to chill, and to know what its parts are doing

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2
Q

four main groups of stimuli

A
  • touch
  • temperature
  • pain
  • body position
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3
Q

touch - skin

A
  • can be hairy or glabrous
  • largest sensory organ
  • protects
  • prevents evaporation
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4
Q

mechanorecptors of the skin

A
  • each has unmyelinated axon branches with mechanosensitive ion channels
  • pacinian corpuscle
  • ruffini’s endings
  • meissner’s corpuscle
  • merkel’s discs
  • krause end bulbs
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5
Q

pacinian corpuscle

A

deep in the dermis, large enough to be seen with your naked eye

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6
Q

ruffini’s endings

A

found in both hairy and glabrous skin

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7
Q

meissner’s corpuscle

A

located in the ridges of glabrous skin (fingertips)

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8
Q

merkel’s discs

A

found in the epidermis, consists of nerve terminal and flattened non-neural epithelial cell

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9
Q

krause end bulbs

A

lie in the boarder regions of dry skin and mucous membrane, the nerve terminals look like the knotted balls of string

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10
Q

which mechanoreceptors have small receptive fields?

A

meissner’s corpuscles and merkel’s discs

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11
Q

which mechanoreceptors have large receptive fields?

A

pacinian corpuscles and ruffini’s endings

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12
Q

which mechanoreceptors are fast adapting?

A

meissner’s and pacinian corpuscles

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13
Q

which mechanoreceptors are slow adapting?

A

merkel’s discs and ruffini’s endings

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14
Q

follicles

A
  • innervated by free nerve endings
  • where hair grows
  • bending of hair causes change in AP firing rate
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15
Q

which mechanoreceptor is most sensitive to 200-300 Hz vibrations?

A

pacinian corpuscles

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16
Q

which mechanoreceptor is most sensitive to 50 Hz vibrations?

A

meissner’s corpuscles

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17
Q

what happens when mechanoreceptor membrane is deformed?

A

mechanosensitive channels open, depolarizing receptor potential

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18
Q

prolonged stimulation causes…

A

decreased receptor potential

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19
Q

two point discrimination

A

our ability to tell the detailed features of a stimulus

* varies across the body

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20
Q

why are fingertips most sensitive to two point discrimination?

A
  • more mechanoreceptors
  • small receptive fields
  • more brain power
  • high resolution mechanisms
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21
Q

primary afferent axons

A
  • bring info to brain or spinal cord
  • enter at dorsal roots
  • varying diameters and size correlate with the type of receptor
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22
Q

which primary afferent axon type is slowest?

A

C fibers (unmyelinated)

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23
Q

spinal cord

A

30 pairs of dorsal and ventral roots

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24
Q

cervical (c)

A

1-8

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25
Q

thoracic (t)

A

1-12

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26
Q

lumbar (l)

A

1-5

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27
Q

sacral (s)

A

1-5

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28
Q

spinal nerves

A

pass through notches in vertebral column

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29
Q

dermatome

A

area of skin innervated by both dorsal roots of a single spinal segment

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30
Q

what is the relationship between spinal segments and dermatomes?

A

one to one

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31
Q

what happens when dermatomes are mapped?

A

delineate a set of bands on the body surface

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32
Q

adjacent dorsal roots innervate….

A

overlapping areas

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33
Q

shingles - herpes zoster (chickenpox)

A

infection of dorsal root ganglion

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34
Q

each half of spinal gray matter is divided into…

A
  • dorsal horn
  • intermediate zone
  • ventral horn
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35
Q

second-order sensory neurons

A

neurons that receive sensory input from primary afferents

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36
Q

A-beta axons

A
  • large
  • synapse on second-order sensory neurons
  • also send axons to brian
  • responsible for perception
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37
Q

dorsal column-medial lemniscal pathway

A
  • for touch and vibration

- A-beta sensory axons travel to brain on IPSILATERAL side through dorsal column

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38
Q

dorsal column axons

A
  • connect to dorsal column nuclei at medulla-spinal cord junction
  • decussate, sensory info is now CONTRALATERAL
  • ascends in medial lemniscus
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39
Q

medial lemniscus

A

travels through medulla, pons, and midbrain to ventral posters (VP) nucleus of the thalamus, which then goes to the primary somatosensory cortex (S1)

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40
Q

lateral inhibition

A

neighboring cells inhibit one another

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41
Q

dorsal column nuclei and thalamic nuclei are..

A

relays that alter info as it passes through

42
Q

trigeminal touch pathway

A

sensation in face carried through trigeminal nerves (CNV)

43
Q

trigeminal nerve

A
  • enters the pons
  • innervates face, mouth, dura mater, tongue
  • synapse on IPSILATERAL trigeminal nucleus, decussates, then thalamus, then S1
44
Q

some sensation comes from which other cranial nerves?

A

VII, IX, X

45
Q

somatosensory cortex

A
  • in partiel lobe

- most complex levels of processing

46
Q

S1 - primary somatic sensory cortex

A
  • brodmann’s area 3b
  • input from VP of thalamus
  • highly responsive to only somatosensory input
  • lesions impair somatic sensation
  • electrical stimulation causes sensation
47
Q

brodmann’s area 3a

A

receives dense input from thalamus like 3b but focus on body position rather than touch

48
Q

brodmann’s area 1

A
  • receives info from area 3b

- mainly texture info

49
Q

brodmann’s area 2

A
  • receives info from area 3b

- emphasizes size and shape

50
Q

layer IV

A
  • where thalamic input terminates

- project to other layers

51
Q

mountcastle’s idea

A

cells with similar characteristics in vertical columns in S1

52
Q

somatotopy

A

mapped by S1 stimulation or by recording from S1 neurons after somatic stimulation

53
Q

another name for somatotopy mapping

A

homunculus

54
Q

features of somatotopy mapping

A

size of cortical sensory region determined by density and importance of input

55
Q

somatotopic map plasticity

A

map changes based on loss or increased use

- use fMRI in humans

56
Q

phantom limb

A

feeling for missing limb by stimulating regions whose S1 representations border those of the limb

57
Q

posterior partiel cortex

A
  • brodmann’s area 5 and 7
  • large receptive fields
  • elborate stimulus preferences
  • integrates with visual, attention, and movement
58
Q

agnosia

A

inability to recognize objects

59
Q

neglect

A

part of body or world ignored

- usual left side ignored due to right hemisphere damage

60
Q

posterior partiel cortex is essenital for…

A
  • perception and interpretation of spatial relationships
  • body image
  • coordinated body movements
61
Q

nociceptors

A

free, branching, unmyelinated nerve endings that signal that body tissue is being damaged or is at risk of being damaged

62
Q

pain

A

the feeling, or perception, of irritating, sore, aching, throbbing, miserable, or unbearable sensations arising from part of the body

63
Q

nociception

A

the sensory process that provides signals that trigger pain

64
Q

types of damaging stimuli

A
  • oxygen deprivation
  • chemicals
  • temperature extremes
  • mechanical stress
65
Q

what causes mechanically gated channels to depolarize and release AP?

A

being stretched or deformed

66
Q

some channels open in response to…

A
  • proteases: enzymes that digest proteins
  • ATP
  • K+
  • bradykinin
  • H+
67
Q

temperature range for warmth

A

37-43 C

68
Q

heat above what temperature causes tissues to burn?

A

43C

69
Q

production of what leads to H+ build up in extracellular fluid?

A

lactic acid

70
Q

what depolarizes nociceptors?

A

histamine

71
Q

polymodal nociceptors

A

respond to thermal, chemical and mechanical stimuli

72
Q

hyperalgesia

A

unusual sensitivity to skon, joints, or muscles that have already been damaged or inflamed

73
Q

features of hyperalgesia

A
  • increased intensity
  • reduced threshold
  • spontaneous
74
Q

sensitizing chemicals

A
  • bradykinin
  • prostaglandins
  • substance P
75
Q

bradykinin

A

stimulates long-lasting intracellular changes that make heat-activated ion channels more sensitive

76
Q

prostaglandins

A

chemicals generated by enzymatic breakdown of lipid membrane

77
Q

substance P

A

a peptide synthesized by nociceptors; causes vasodilation and release of histamine

78
Q

first pain

A

fast and sharp due to A-gamma fibers

79
Q

second pain

A

dull and longer de to C fibers

80
Q

primary afferent cell bodies

A
  • in dorsal root ganglia
  • branch out of lissauer
  • synapse on substantis gelatinosa neurons
81
Q

what is the NT for the pain afferents?

A

glutamate

82
Q

what stimulates substance P release?

A

capsaicin

83
Q

capsaicin

A

can be analgesic by depleting substance P from nerve endings

84
Q

referred pain

A

cross-talk between visceral nociceptor activation and cutaneous sensation

85
Q

spinothalamic pathway

A
  • pain and temperature
  • decussate immediately and run in ventrally in tract
  • don’t synapse until thalamus
  • don’t communicate until medial lemniscus
86
Q

trigeminal pain pathway

A
  • small diameter fibers in nerve synapse on neurons in spinal nucleus in brainstem
  • second-order neurons decussate and connect to thalamus vis trigeminal lemniscus
87
Q

afferent regulation of pain

A
  • hyeralgesia
  • reduced by A-beta fiber activity
  • gate theory of pain
88
Q

gate theory of pain

A

certain neurons of the dorsal horns, which project an axon up the spinothalamic that, are excited by BOTH large-diameter sensory axons and unmyelinated axons

89
Q

descending regulation of pain

A

periventricular and periaqueductal great matter (PAG) neurons synapse on raphe nucleus, suppressing pain

90
Q

raphe nucleus

A
  • serotonergic

- project to dorsal horn and depress nociceptive neuron activity

91
Q

opioids

A

poppy, morphine, codeine, heroin

92
Q

opioids produce powerful analgesia as well as…

A
  • mood changes
  • nausea
  • drowsiness
  • mental stupor
  • constipation
93
Q

endorphins

A

endogenous opioids, expressed in pain pathways

94
Q

what is the antagonist of endorphins?

A

naloxone

95
Q

effects of endorphins

A
  • block glutamate release

- hyperpolarize cell

96
Q

what regions of the body have temperature sensitive neurons to help maintain body temperature?

A

hypothalamus and spinal cord

97
Q

temperature sensitive spots are sensitive to…

A

either hot OR cold… NOT BOTH

98
Q

trpv1

A
  • above 43C

- capsaicin

99
Q

trpv8

A
  • below 25C

- methanol

100
Q

when are differences in temperature rates most pronounced?

A

during and right after changes

101
Q

cold receptors

A

A-gamma and C fibers

102
Q

warm receptors

A

only C fibers

NEURO 3000 (16 decks)

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