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NEURO 0010 > somatosensory > Flashcards

somatosensory Flashcards

1
Q

what are the 3 divisions of the somatic sensory system?

A

1) exteroception
(sensing physical force on the skin)
2) proprioception
(position of body parts in space)
3) enteroception
(viceral sensory/internal)

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2
Q

what is exteroception?
what are the 3 types of exteroception?

A

“sensing physical force on the skin”
1) Mechanoreception
2) Thermoreception
3) Nociception

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3
Q

what is mechanorecption?

A

touch
- pressure on skin

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4
Q

what is thermorecpetion?

A

temperature
- difference in tempreature

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5
Q

what is nociception?

A

pain

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6
Q

what is the largest sensory organ?

A

the skin

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7
Q

what are the types of mechanoreceptors?

A
  • merkel’s disk
  • meissners corpuscle
  • pacinian corpuscle
  • ruffini’s ending
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8
Q

merkel’s disk
- consists of
- location
- receptive field size
- adaptation

A
  • consist of a nerve ending and a special epithelial cell
  • closer to surface, glaborus
  • small
  • slow
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9
Q

meissners corpuscle
- location
- receptive field size
- adaptation

A
  • superficial, glabrous skin
  • small
  • rapid adaptation
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10
Q

pacinian corpuscle
- location
- receptive field size
- adaptation

A
  • deep in dermis, hairy and glaborus
  • large
  • rapid
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11
Q

ruffinis ending
- location
- receptive field size
- adaptation

A
  • deep in demis, hairy and glaborus skiN
  • large
  • slow
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12
Q

what factors influence a receptive field?

A

closer to surface of skin -> small RF
deeper in skin -> large RF

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13
Q

what is adaptation?

A

after a certain time, receptors will stop firing even though stimulus is still occurring

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14
Q

what is rapid adaptation?
what is unique about rapid adaptation responses?

A

APs only fired when stimulus is first placed and when stimulus is first removed
- responding to changes in pressure, not the absolute pressure

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15
Q

what does rapid adaption allow for detection of?

A
  • rapidly-changing/high-frequency stimuli (ex. vibrations and texture detection)
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16
Q

what is the relationship between corpuscles and frequencies?

A

the corpuscles mediate different ranges of frequencies

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17
Q

frequency for pacinian

A

200-300Hz (higher)

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18
Q

frequecny for meissners

A

50Hz(lower)

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19
Q

what are capsules?
what is the function of the capsule?

A

Capsules are fluid-filled and continuous stimulus eventually stops deformation of the receptors

rapid adaptation mechanoreceptors have the capsule
- removing the capsule takes away the receptors rapidly adapting capabilities and instead makes it slow adapting

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20
Q

what does capsulation have to do with vibration?

A

as you slide skin over different surfaces, varying textures result in varying degrees of friction

pacinian=high frequency
- finer materials like silk

meissner=low frequency
- rougher materials

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21
Q

what are the axons of mechanoreceptors like?
- what to they contain

A
  • have unmyelinated axon terminals
  • the membranes of these axons have mechnosensitive ion channels that convert mechanical force into a change if ionic current
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22
Q

what do mechano receptors respond to?

A

force applied to the channels either makes them open more or less

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23
Q

how is the force applied?

A

directly or indirectly
- through other components of the cell like intracellular cytoskeletal components

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24
Q

what is internal modulation?

A

mechanical stimuli can trigger release of second messengers (DAG, IP3)

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25
Q

what does the 2 point discrimination task measure?

A

the spatial resolution that varies across the body
or
spatial acuity

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26
Q

what are ion channels sensitive to?

A

membrane stretching and deformatiy

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27
Q

what is spatial acuity influenced by?

A

1) receptive field size
2) density of receptors

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28
Q

receptive field and density of receptors relationship to spatial acuity

A
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29
Q

how are areas of the body mapped onto the brain?

A

topographic map

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30
Q

what factor is present in the topographic map of the brain?

A

cortical magnification

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31
Q

what does the size of the cortex devoted to an area correlate to?

A
  • the density of receptors in that area
  • the spatial acuity of that area
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32
Q

what is cortical magnification directly proportional to?

A
  • small receptive fields
  • high density of receptors
  • high spatial acuity
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33
Q

what are primary afferent axons, what do they do?

A

they bring information from sensory receptors into the CNS (spinal cord)

34
Q

where do they enter the spinal cord through?

A

the dorsal root ganglia

35
Q

what is unique about their axons?

A

they have different diameters and amounts of mylein

36
Q

what are the 4 types of primary afferent axons?

name them from thickest and fastest
to thinest and slowest

A
37
Q

Aa axons sensory receptors?

A

proprioceptors of skeletal muscle

38
Q

Ab sensory receptors?

A

mechanoreceptors of skin

39
Q

Adelta sensory receptors?

A

pain, temperature

40
Q

C fiber sensory receptors?

A

temperature, pain, itch

41
Q

what 4 groups are the spinal cords divided into?
- name, numbers, body part

A

Cervical: C1- C8 (neck and arms)
Thoracic: T1-T2 (torso)
Lumbar: L1-L5 (legs)
Sacral: S1-S5

42
Q

what is a dermatome?

A

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

43
Q

what does the DCML pathway include?

A

touch, vibration, limb position and tactile sensation

44
Q

DCML pathway

A

1) primary afferents go enter spinal cord through dorsal horn
2) goes through ipsilateral side of dorsal column
3) synapses in dorsal column nuclei
4) decussates in spinal cord and medulla junction
5) goes through contralateral medial lemniscus
6) synapse on ventral posterior lateral nucleus on thalamus
7) thalamus projects to primary somatosensory cortex

45
Q

what is S1 also called?

A

3b

46
Q

where do the thalamic inputs of S1 go?

A

S1 terminate maily in layer 1V

47
Q

what areas does layer 4 project to?
what do these areas do?

A

area 1
- texture information

area 2
- size and shape

48
Q

how does the S1 organize itself column wise?

A

are stacked vertically into columns
according to
- neurons with similar inputs and responses

49
Q

what happens if you were to remove input? (ex. nerve block, amputation)

A
  • lose cortical area dedicated to this input
  • surrounding areas grow into that region
50
Q

what happens if you overstimulate input?

A
  • cortical area dedicated to this input grows into surrounding aread
51
Q

how are phantom limbs described?

A
  • can still feel sensations in limb that is no longer present
  • cortical area of missing limb activated by lateral connections
52
Q

What does the posterior partietal complex (PPC) consist of?

A
  • areas 5
  • areas 7
53
Q

describe PPC neurons receptive field?

A
  • have large RFs with stimulus preferences that are a challenge to characterize because they are so elaborate
54
Q

what are the PPC areas concerned with?

A
  • somatic sensation
  • visual stimuli
  • movement and planning
  • persons state of attentiveness
55
Q

what are the 2 syndromes that are a result of PPC damage?

A

Agnosia
- inability to recognize objects even though sensory systems are intact

Hemineglect
- happens contralateraly

56
Q

describe nociceptor neurons?

A
  • free branching, unmylenated nerve endings that signal body tissue is being damaged or is at risk of being damaged
57
Q

difference between pain and nociception?

A
  • pain is perceived
  • nociception is the process that triggers the sensation of pain
58
Q

hyper algesia vs. analgesia?

A

hyperalgesia
- elevation of pain sensitivity: two types

analgesia
- inability to feel pain

59
Q

describe referred pain?

A

the sensation of pain in a certain place despite there being no tissue damage

60
Q

how does referred pain occur?

A

axons carrying pain information from visceral organs enter the spinal cord at the same location as the axons from the periphery

sometimes crossing over of signaling occurs

61
Q

what are the types of nociceptors?

A
  • mechanical
  • thermal
  • chemical
  • polymodal
62
Q

describe TRPv receptors?

A

they are receptors that open to cause the first depolarization that triggers an action potential

63
Q

what would happen if TRPv channels were blocked?

A

blocking TRPv or voltage gated VG Na channel will disturb nociception
- person will not feel as much pain

64
Q

what does hyperalgesia cause?

A

local tissue damage
- causes blood vessels to dialate and mass cells to release histamine

65
Q

in what way are noiceceptors the opposite of adaptation?

A
  • longer stimulus more stimulus fires
  • pain can grow overtime
66
Q

what is SCN9A?

A

it codes for the Nav17 channel
- people who have a hypersensitivity or insensitivity to pain have a mutation in this channel

67
Q

what axons are responsible for slow vs. fast pain?

A

fast
- Aa & Ab

slow
- Ad and B

68
Q

describe the mylenation of Ad and C fibers?

A

Ad = thinly mylenated
C fibers = unmylenated

69
Q

describe delta pain?

A

sharp, stinging, local, transient

70
Q

describe c fiber pain?

A

dull, aching, poorly localized, enduring

71
Q

what are receptor potentials generated by?

A

TRPV(capsian) channels and Nav 17 channels

72
Q

what are action potentials generated by?

A

voltage gated sodium Na17 channels start the action potential and propagate it down the axons to the CNS

73
Q

what does the spinothalamic (anterolateral pathway) do?

A

mediates protopathic component of somatosensory system
- pain, temperature, itch

74
Q

what are the 2 key differences in the pathways?

A
  • first synapse found in dorsal horn
  • decussates immediatley in spinal cord
75
Q

what are the 2 key differences in the pathways?

A
  • first synapse found in dorsal horn
  • decussates immediately in spinal cord
76
Q

what is different about the axons ascending up the anterolateral pathway?

A
  • have wider range of synapses
  • final projections go to somatosensory cortex
77
Q

damage and decussation?

A

damage pathway above/before
- the impairment occurs on the same side

damage pathway after/below
- damage occurs on the opposite side of the body

78
Q

what is the “soup” that causes inflamation?

A
  • bradykinin
  • substance p (vasodilation due to increased histamine)
79
Q

what is primary vs secondary algesia?

A

primary = directly at site of damage
secondary = around site of damage

80
Q

what is the descending pain control pathway?

A

1) periaqueductal gray around the cerebral aqueduct
2) signals raphe nuclei in medulla
3) affects nociceptive inputs in the dorsal horn of the spinal cord

81
Q

what can the descending pain pathway be activated by?
what is its purpose?

A
  • emotional factors
  • opioids

purpose
- pain doesnt register in the brain

82
Q

opioid vs. naloxone?

A

opioid = agonist
naloxine = antagonist

NEURO 0010 (22 decks)

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