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Psych 3 > Somatosensation (Lecture 6) > Flashcards

Somatosensation (Lecture 6) Flashcards

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1
Q

somatosensation

A

the “body senses”, deals with processing stimuli

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2
Q

3 separate but interactive systems of somatosensation

A

exteroceptive system
proprioceptive system
interoceptive system

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3
Q

skin

A

largest sensory organ, heaviest organ in the body, function is to prevent fluid from escaping, protection from dirt and pathogens, and report info about stimuli it comes in contact with

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4
Q

two types of skin

A

hairy and glabrous (hairless skin)

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5
Q

two layers of skin

A

epidermis and dermis

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6
Q

epidermis layer of skin

A

outermost layers, including several layers of dead skin cells

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7
Q

dermis layer of skin

A

inner layers, including matrices of glands, blood vessels, muscle, and hair

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8
Q

hypodermis layer of skin

A

layer of connective adipose tissue

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9
Q

mechanoreceptors

A

receptors that respond to mechanical stimulation such as pressure and stretching, change in conformation leads to opening of ion channels and membrane depolarization

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10
Q

4 basic types of mechanoreceptors

A

Meissner Corpuscles
Pacinian Corpuscles
Merkel’s Disks
Ruffini’s endings

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11
Q

Meissner Corpuscles

A

respond to light tapping (touch) and flutter, found on hairless skin (lips, fingertips, palms, nipples), small receptive field

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12
Q

Pacinian Corpuscles

A

respond to pressure and vibration, large receptive field (intestines and genitalia), located deep within dermis in both skin types

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13
Q

Merkel’s Disks

A

sensitive to fine detail and mechanical stimulation, small receptive fields (ridges of fingertips), located in outer layer of skin (epidermis)

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14
Q

Ruffini’s endings

A

respond to stretching of skin, proprioception, large receptive field, found on both types of skin (hairy and non-hairy)

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15
Q

touch information travels:

A

FAST (due to heavy myelination which increases speed of electro-transmission)

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16
Q

review: dorsal vs. ventral

A 
dorsal= sensory
ventral= motor
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17
Q

mechanoreceptor cell bodies are located in the:

A

Dorsal Root Ganglion (DRG)

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18
Q

sensory information enters the spinal cord through the:

A

dorsal horn

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19
Q

properties of the spinal nerves

A

there are 30 spinal nerves, each nerve has a dorsal root and a ventral root, enters spinal cord through notch in vertebrae

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20
Q

touch acuity

A

the ability to distinguish a separation between two closely adjacent stimuli applied to the skin, “two point” discrimination

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21
Q

touch information travels:

A

FAST (due to heavy myelination which increases speed of electro-transmission)

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22
Q

dermatome

A

the area of skin innervated by right and left dorsal roots of a single spinal segment

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23
Q

what happens to adjacent dorsal roots in innervation

A

adjacent dorsal roots slightly overlap in innervation

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24
Q

review: grey matter vs. white matter

A

grey matter contains cell bodies, white matter is myelination for axons

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25
Q

sensory information travels in 2 paths

A
  1. to interneurons in dorsal horn= rapid reflex response

2. up spinal cord to dorsal columns all the way to the brain for conscious perception of the stimuli

26
Q

asomatognosia

A

the failure to recognize parts of one’s own body (neglect syndrome, right hemi damage), result of damage to somatosensory association cortex

27
Q

DCML “Dorsal Column-Medial Lemniscus Pathway”

A

the ascending touch pathway:

  • ascend ipsilaterally through dorsal column nuclei in medulla
  • decussate at level of medulla, info transmitted contralateral
  • ascend white matter tract
  • synapse in ventro-posterior (VP) thalamus
  • project to primary somatosensory cortex
28
Q

cortical mapping of somatosensation

A

founded by Wilder Penfield, mapped out S1 using electrical circuits on the brain to determine where different parts of the body were mapped

29
Q

primary SS cortex names

A

post central gyrus= primary somatosensory cortex: S1, 3b, parietal lobe

30
Q

homunculus

A

concept of a topographical map of the body in the SS cortex, is “little man” in Latin, body part mapping is not proportional or continuous

31
Q

corresponding area in the cortex is proportional to:

A

sensitivity of that body region

32
Q

different regions of skin have different sensitivities due to:

A

variation in receptor type and density and differences in amount of brain tissue dedicated to sensory input from that area= “importance”

33
Q

Phantom Limb

A

compelling perception that an amputated limb or organ is still attached to the body and functioning, can be frustrating, painful, itchy, feel on fire, previously considered a psychological disorder

34
Q

explanation of phantom limb:

A

rewiring of the brain to adjacent area, it is a result of reorganization of S1 cortical map, proven by fMRI activation of cortical regions devoted to missing limb (ex: activation of area devoted to amputated arm when stimulate face)

35
Q

collateral sprouting

A

new branching of undamaged axons to vacant area (can be good, bad, or neither)

36
Q

neuroplasticity

A

neurons from adjacent body parts in S1 grow into vacant synapses and relay info to association cortices

37
Q

reason for plasticity

A

cortical reorganization occurs due to lack of input in adjacent areas (proven through owl monkey study with amputated finger)

38
Q

association somatosensory cortex

A

S1 -> somatosensory association cortex (posterior parietal lobe)= bilateral info from both sides of body is processed

39
Q

damage to somatosensory association cortex results in:

A

astereognosia or asomatognosia

40
Q

astereognosia

A

inability to recognize objects by touch, result of damage to somatosensory association cortex

41
Q

asomatognosia

A

the failure to recognize parts of one’s own body (neglect syndrome, right hemi damage), result of damage to somatosensory association cortex

42
Q

thermoreceptors

A

receptors that respond to certain temperatures and changes in temperature, free nerve endings, both warm and cold receptors

43
Q

warm receptors

A

fire to increase in temperature or steady high temperature, located deep within the dermis, Action Spectrum (86-118F)

44
Q

cold receptors

A

fire to decrease in temperature or steady low temperature, located close to the surface, action spectrum (68-113F)

45
Q

response to extreme temperatures:

A

nociceptors that respond to extreme temperatures, related to pain, non-selective ion channels activated by heat > 43C, some cold receptors have cation channels too

46
Q

nociceptors

A

free nerve endings activated by stimuli that have potential to cause tissue damage (i.e. pain)

47
Q

location and activation of nociceptors

A

distributed throughout the skin, muscles, joins, and connective tissue (none in brain), some activated by pressure in the joints, some activated by chemicals released from damaged tissue (puncture)

48
Q

pain and temperature cell bodies live in:

A

DRG

49
Q

axons enter spinal cord through:

A

dorsal root

50
Q

afferents divide into 2 branches: (for pain/temp)

A

travel a bit up spinal cord in zone of lussauer, or synapse on a secondary neuron that decussates and travels up spinothalamic tract to brain

51
Q

pain and temperature path (spinothalamic pathway)

A
  • info enters the dorsal root and synapses on secondary neurons
  • secondary neuron decussates immediately and ascends the spinal cord in the spinothalamic tract
  • synapses in the ventral posterior (VP) nucleus of the thalamus
  • projects to primary somatosensory cortex
52
Q

pain information travels:

A

SLOWER than touch info (due to less myelination on axons)

53
Q

2 types of afferent fibers for pain/temp:

A

small and myelinated- faster response to pain (sharp pain), then small and unmyelinated- slower response to pain (dull ache)

54
Q

spinothalamic pathway

A

path pain and temperature information takes to get from stimuli to S1

55
Q

differences between DCML and spinothalamic paths

A

DCML- (touch), synapses on medulla, doesn’t cross midline until midbrain. Spinothalamic- (pain and temp), synapses upon entering spinal cord, crosses midline almost immediately

56
Q

Brown-Sequard Syndrome

A

constellation of sensory and motor signs following damage to one side of spinal cord (because pain and touch signals cross at different areas)

57
Q

descending modulation of pain

A

electrical stimulation of the periaqueductal gray (PAG) has analgesic effects

58
Q

PAG as modulation of pain

A

PAG receives info from brain regions related to emotion, and strong emotion= PAG excitation through disinhibition

59
Q

opitates:

A

act on receptors for endogenous opioids/endorphins

60
Q

acupuncture

A

system of complementary medicine that involves pricking the skin or tissue with needles, used to alleviate pain

61
Q

placebo effect

A

measurable, observable, or felt improvement in health or behavior not attributable to medication or treatment

62
Q

why does acupuncture or placebo effect work?

A

this type of pain relief block pain by u-opioid receptor blockers, activation of endogenous opioids

Psych 3 (13 decks)

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