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4. BIOL257 > Somatosensory system: > Flashcards

Somatosensory system: Flashcards

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1
Q

somatosensory receptors: types

A
  • general somatic afferents (GSA)

- general visceral afferents (GVA)

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2
Q

somatosensory receptors: general somatic afferents

A
  • cutaneous = exteroceptors

- muscles, tendons, joints = proprioceptors

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3
Q

somatosensory receptors: general visceral afferents

A
  • internal organs (viscera) = enteroreceptor
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4
Q

cutaneous receptors: mechanoreceptors

A
  • touch
  • pressure
  • vibration
  • stretch
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5
Q

cutaneous receptors: thermoreceptors

A
  • hot

- cold

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6
Q

cutaneous receptors: nociceptors

A
  • intense mechanical
  • intense hot and cold
  • chemicals
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7
Q

mechanoreceptors (non-nociceptive): typical features

A
  • low threshold (highly sensitive)
  • glutamatergic
  • predominantly A-beta afferent nerve fibres (large, myelinated, fast)
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8
Q

hair follicle (peritrichial) receptors (RA1): features

A
  • detects bending of hairs (air movement, touch)
  • bending of hair stretches membrane
  • opens mechanically gated cation channels in membrane of afferent fibre
  • depolarisation –> action potentials
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9
Q

hair follicle (peritrichial) receptors (RA1): non-encapsulated endings

A
  • single process of an afferent sensory fibre, wrapped in spiral around base of hair
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10
Q

hair follicle (peritrichial) receptors (RA1): adapting

A

rapid adapting

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11
Q

hair follicle (peritrichial) receptors (RA1): receptive field

A

small receptive field

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12
Q

Meissner’s corpuscle (RA1): features

A
  • glabrous (hairless) skin only (eg. fingertips)
  • superficial location
  • sheath of ct, packed w pancake-like stack of pear-shaped Schwann cells (teloglia)
  • compression causes mechanically gated cation channels in membrane to open
  • depolarisation -> action potentials
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13
Q

Meissner’s corpuscle (RA1): good for and adapting

A
  • discriminative touch
  • grip
  • touch

rapid adapting

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14
Q

Meissner’s corpuscle (RA1): receptive field

A
  • encapsulated capsule

- small receptive field

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15
Q

Pacinian corpuscle (RA2): good for and adapting

A
  • pressure and vibration

- rapid adapting (sustained pressure dissipates)

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16
Q

Pacinian corpuscle (RA2): receptive field

A
  • large receptive field
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17
Q

Pacinian corpuscle (RA2): pressure causes

A
  • mechanically gated Na channels in afferent nerve ending to open-> depolarise cell -> AP
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18
Q

Pacinian corpuscle (RA2): features

A
  • concentric layers of flattened fibroblasts (ct)

- viscous fluid in btw

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19
Q

duplex theory: tactile texture perception - depends on

A
  • spatial cues

- temporal cues

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20
Q

duplex theory: tactile texture perception eg. spatial cue

A
  • size

- shape

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21
Q

duplex theory: tactile texture perception eg. temporal cues

A
  • rate of vibration as object moved across skin
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22
Q

duplex theory: tactile texture perception for fine texture

A
  • spatial cues alone can’t be used in static touch

- must move fingers across surface

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23
Q

duplex theory: tactile texture perception vibration sensitivity from

A
  • high freq vibration receptors (Pacinian corpuscles RA2)
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24
Q

Merkel cell - neurite complex (SA1): features and adapting

A
  • superficial (lips, fingertips)
  • discriminative touch and pressure
  • edges of objects (shape, curvature) texture
  • slow adapting
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25
Merkel cell - neurite complex (SA1): receptive field
- small receptive field
26
Merkel cell - neurite complex (SA1): mechanism
- afferent fibre terminals (neurites) form disks which are mechanoreceptive - discs contact epidermal cells (Merkel)
27
Merkel cell - neurite complex (SA1): merkel cell job
- also mechanoreceptive | - release NT glutamate onto afferent terminals (disks) -> depolarisation -> AP
28
Ruffini's corpuscles (SA2): adapting and field
- slow adapting | - large receptive field
29
Ruffini's corpuscles (SA2): for and located
- stretching of skin (ligs, tendons) - joint position (kinaesthesia and proprioception) - long axis along stretch lines of skin
30
Ruffini's corpuscles (SA2): features
- thin, cigar shaped capsule deep in skin - interior of capsule have ct - branched terminals of primary afferent sensory fibre lie btw strands
31
Ruffini's corpuscles (SA2): mechanism
- stretching compresses mechanoreceptive nerve terminals - opens cation channels - depolarises primary afferent -> AP
32
free nerve endings- mechanoreceptive (non-nociceptive): features
- terminal branches of afferent fibres (Type C, unmyelinated) btw epidermal cells - membrane distortion opens mechanically gated cation channels
33
free nerve endings- mechanoreceptive (non-nociceptive): adaptive and receptive field
- slow adapting small field: pleasant touch large field: crude 'non-discriminative' touch
34
free nerve endings-general visceral afferents: faetures
- most visceral receptors are also free nerve endings | - mostly subconscious sensory pathways (visceral autonomic reflexes)
35
free nerve endings-general visceral afferents: types
- mechanoreceptors - chemoreceptors - nociceptors
36
free nerve endings-general visceral afferents: mechanoreceptor eg
mechanoreceptor: - walls of hollow organs, blood v - eg. aortic arch - respond to increase in BP -> vasodilation and lower heart rate
37
free nerve endings-general visceral afferents: chemoreceptor eg
- blood gases - blood pH - trigger compensatory respiratory and cardiovascular changes
38
free nerve endings-general visceral afferents: nociceptor eg
- signal pain | - excessive distention of an organ
39
free nerve endings- thermoreceptors (RA2): adapting and receptive field
- rapid adapting | - large receptive
40
free nerve endings- thermoreceptors (RA2): features
- superficial layers of skin | - transduction = temperature sensitive transient receptor potential (TRP) ion channels
41
free nerve endings- thermoreceptors (RA2): non-nociceptive thermal sensation
warm: 29-45˚ maximal activity at 45˚ cold: 5-40˚ maximal activity at 25˚
42
TRP channels and thermoreception: features
- non specific cation channels (Ca, Na) - different TRP variants for dif temp - activation cause influx of cations and depolarisation of cell -> increase firing of AP
43
TRP channels and thermoreception: TRP channel agonists
- chilli and mint
44
thermoreceptors: features
- rapidly adapting (best when temp changes) | - signal direction of temp change
45
thermoreceptors: eg. drop in temp
- momentarily silences warm receptors while cold receptors show burst in firing - vice versa
46
thermoreceptors: perceived temp
comparing relative activities of warm and cold receptors | - population coding
47
proprioceptors: list types
- muscle spindle Type Ia - muscle spindle Type II - golgi tendon organs - ruffini's corpuscles - pacinian corpuscles
48
proprioceptors: located in mm
- muscle spindle Ia, II
49
proprioceptors: located in tendons
- golgi tendon organs
50
proprioceptors: located in joint capsule
- ruffini's corpuscle | - pacinian corpuscle
51
proprioceptors: modality- muscle spindles
Ia: rate of mm stretch II: degree of mm stretch
52
proprioceptors: modality- golgi tendon organs
- tendon stretch
53
proprioceptors: modality- ruffini's and pacinian corpuscles
- stretch in articular cap
54
proprioceptors: adaptation slow
- muscle spindle II - golgi tendon organs - ruffini's corpuscles
55
proprioceptors: adaptation fast
- muscle spindle Ia | - pacinian corpuscles
56
ascending sensory pathways: generalised circuit has
- 1st, 2nd and 3rd order neurons
57
ascending sensory pathways: generalised circuit - 1st order neuron
- pseudounipolar - transmits sensory info from PNS to CNS - cell body usually in ganglion - synapse w 2nd order in spinal cord/ brainstem
58
ascending sensory pathways: generalised circuit - 2nd order neuron
- multipolar neuron - relay sensory info from spinal cord/ brainstem to thalamus - also (reticular system, limbic, cerebellum)
59
ascending sensory pathways: generalised circuit - 3rd order neuron
- multipolar | - relay sensory info from thalamus to cortex where conscious sensory perception occurs
60
ascending sensory pathways: lateral spinothalamic (ALS) pathway for
body: - pain - temp
61
ascending sensory pathways: anterior spinothalamic (ALS) pathway for
body: - crude (non-discriminative) touch - pressure
62
ascending sensory pathways: dorsal column-medial lemniscal (DCML) for
body - discriminative touch - pressure - kinaesthesia - conscious proprioception
63
ascending sensory pathways: face- discriminative touch and pressure, kinaesthesia
- primary trigeminal (pons)
64
ascending sensory pathways: face- pain, temp, crude touch, pressure
spinal trigeminal (cervical cord)
65
ascending sensory pathways: pain and pressure in viscera
spinothalamic (ALS)
66
ascending sensory pathways: subconscious
- most proprioceptive info not processed consciously, directed to cerebellum without passing thalamus
67
ascending sensory pathways: spinocerebellar, spinohypothalamic for
- subconscious proprioception | - autonomic activation
68
ascending sensory pathways: subconscious pathway/ target/ function- proprioceptors
- post spinocerebellar - cerebellum - coordination of mm movements - maintain posture
69
ascending sensory pathways: subconscious pathway/ target/ function- mechanoreceptors
- ant spinocerebellar - cerebellum - coordination of mm movements - maintain posture
70
ascending sensory pathways: subconscious pathway/ target/ function- nociceptors/ thermoreceptors in spinohypothalamic pathway
- hypothalamus - autonomic (hormonal etc) - reflex and emotional aspects of pain
71
ascending sensory pathways: subconscious pathway/ target/ function- nociceptors/ thermoreceptors in spinoreticular pathway
- reticular formation - arousal - alertness - evading injury
72
spinothalamic pathway: primary afferents
terminate in spinal cord (dorsal horn) - nociceptors - thermoreceptors - mechanoreceptors (crude touch, pressure)
73
spinothalamic pathway: 2nd order neurons will
- decussate in spinal cord, travel contralaterally and terminate in - thalamus (ventral-post complex) - reticular formation (arousal, alertness)
74
spinothalamic pathway: 3rd order neurons will terminate in
- primary somatosensory cortex (SI) - discrimination | - limbic cortex (cingulate gyrus, insular cortex) - hypothalamus - affective motivatinal
75
dorsal column-medial lemniscal pathway: primary afferents
- mechanoreceptors - proprioceptors - axons ascend ipsilaterally in dorsal columns and terminate in medulla: - cuneate nucleus (upper body) - gracile nucleus (lower body) - collaterals (reflexes) terminate in spinal cord (dorsal horn)
76
dorsal column-medial lemniscal pathway: 2nd order
- axons decussate forming medial lemniscus (sensory decussation) - terminate in thalamus (ventral post complex)
77
dorsal column-medial lemniscal pathway: 3rd order
- terminate in primary somatosensory cortex (SI) -> discrimination
78
trigeminothalamic pathway: features
- principal somatosensory nerve of head | - sensory info from face, nose, mouth, teeth, eyes, (excl. retina), dura, blood vessels
79
trigeminothalamic pathway: branches
- ophthalmic n - maxillary n - mandibular n
80
trigeminothalamic pathway: primary afferents
- converge in trigeminal n
81
trigeminothalamic pathway: 1st soma
trigeminal ganglion (PNS)
82
trigeminothalamic pathway: 2nd soma
various nuclei in brainstem and cervical spinal cord
83
trigeminothalamic pathway: 3rd
thalamus (ventral post)
84
parietal lobe: somatosensory cortex SI primary
- postcentral gyrus - somatotopic organisation - raw somatosensory info from thalamus - encodes type, intensity, localisation of sensory input
85
parietal lobe: somatosensory cortex SII secondary
- parietal operculum/ upper lip of lateral sulcus - somatotopic organisation - high order somatosensory functions (sensorimotor integration, integration of bilateral sensory info, attention, learning, memory)
86
sensory homunculus:
- area of cortex devoted to given body region is proportional to sensory input (no. of sensory afferents) from that region vs physical SA
87
dermatome: define
- sensory region on surface of body that sends afferents via spinal n
88
parietal lobe: primary somatosensory SI cortex functional organisation
divided into narrow strips -> relate to Brodmann's areas 3a, 3b, 1, 2 - different sensory receptor type - each area in SI has separate somatotopic map
89
parietal lobe: somatosensory cortex columnar organisation
- area 3b: functionally distinct (vertical columns) receive input from SA or RA skin receptors in same body region
90
parietal lobe: somatosensory cortex hierarchal organisation
- cortical neurons show increase in size of receptive field from area 3b - 1 - 2 - 4 - increase complexity of somatosensory processing and intergration
91
parietal lobe: somatosensory cortex -post parietal cortex
- somatosensory association cortex areas 5, 7 - receives input from SI and SII - stereognosis integration of somatosensory and visual input: - dorsal 'where' stream - spatial vision - coordinates motor output via motor cortex - arm, hand, eye movements
92
stereognosis:
haptic (tactile) perception | - perceive and recognise object by touch without visual/ auditory info
93
stereognosis: cues
- size - shape - texture - temp
94
stereognosis: pathway and diagnostic test for
- DC-ML mostly | - for integrity of parietal lobe: postcentral gyrus, parietal association area
95
astereognosis:
- Alzheimer's disease - less in other forms of dementia - disturbance of associative links btw tactile info and memory

4. BIOL257 (18 decks)

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