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Neuro > Somatosensory System I > Flashcards

Somatosensory System I Flashcards

1
Q

Includes the sense of

A

Touch
Proprioceptive sensation
Positional sensation
Vibratory sensation
Fine touch or epicritic touch
Crude touch or epicritic touch
Temperature
Pain

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2
Q

PC-ML system perceives

A

Vibration, kinesthesia, fine touch and spatial discrimination through mechanoreceptors and proprioceptors

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3
Q

Anterolateral system perceives

A

Temperature, pain (fast and slow), and crude touch

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4
Q

Sensory info

A

Reaches the thalamus - synapses w/ next neuron - project to contralateral cortex (somatotopic organization)

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5
Q

Classification of sensory fibers

A

Lloyd’s classification
- I: greater degree of myelination, greater diameter= Faster
- II: smaller diameter, less myelin = fast, but less than type I
- III: narrow diameter, little myelin = slower AP conduct v
- IV: very very narrow diameter, amyelinic = slowest fibres

Gasser classification (A, B, C)
- A-alpha: equivalent to I
- A-beta: equivalent to II
- A-delta: equivalent to III
- C: equivalent to IV

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6
Q

Sensations and types of fibers that it uses

A

Golgi tendons (proprioception) —> Ib
Muscle spindles —> Ia / II
Pain and temperature (ALS) —> III, IV

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7
Q

Classification motor fibers

A

Alpha and gamma (fast and slow) for somatic efferents.

B and C fibers for autonomic nervous system:
- B = preganglionic, little myelination, faster
- C = postganglionic, no myelin, slower

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8
Q

Types of muscles fibers in muscle spindles

A

Extrafusal
Intrafusal

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9
Q

Extrafusal muscle fibers

A

Make force

  • Slow: type I
  • Fast: type IIa, IIb
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10
Q

Intrafusal muscle fibers

A

Part of sensory organs
Proprioperception in muscles (house muscle spindles)

  • Nuclear bag intrafusal fiber
  • Nuclear chain intrafusal fiber
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11
Q

Neuromuscular spindles - location, composition

A

Within muscles
Composed of muscle fiber + a sensory fiber surrounding it
Motor fiber can be surrounded by:
- Annulospiral endings: travel in type Ia axons (fastest)
- Flower spray endings: travel in type II axons

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12
Q

How do neuromuscular spindles work?

A

They have mechanoreceptors:

Muscle stretched = annulospiral terminals stretched -> activate mechanoreceptors (detect degree of muscle stretching)

Stretch = stimulus for reflex: activate motor fibre to generate reflex + send fibers to cortex (reflex = conscious) and to cerebellum for proprioception.

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13
Q

The muscle spindle involves

A

terminals surrounding actual muscle fibres

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14
Q

The muscle spindle involves terminals surrounding actual muscle fibres, and therefore:

A

Muscle stretched —> spindle stretched
Muscle contracted —> spindle contracts (can be detected)

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15
Q

Why are the nerve terminals surrounding muscle fibres?

A

So we can know when the muscle is being stretched involuntarily

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16
Q

Little intrafusal fibers are innervated by

A

Gamma-motor neurons

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17
Q

Normal muscle fibers (extrafusal) are innervated by

A

A-alpha fibers

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18
Q

Annulospiral terminals detect

A

Speed of stretch
(Ia fibers are fired when the change is fast)

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19
Q

Flower spray terminals detect

A

Degree of stretch
(type II are fired mostly when stretch degree changes a lot)

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20
Q

Golgi tendon organ - location, detects

A

Located in the tendons
Detects the degree of tension (not stretching)

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21
Q

Golgi tendon organ - fibers

A

Type Ib fibers

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22
Q

Golgi tendon organ - mechanism of action

A

Stimulus conveyed by Ib fibers = inhibitory reflex -> protect us from breaking tendons.
Too much tension = muscle relaxation (inhibitory reflex)

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23
Q

Golgi tendon organ - functions

A

Proprioceptive
Protective

24
Q

Joint receptors - detect

A

Detect position of the joint: whether the joint is extended, flexed,..

25
Q

Joint receptors - fibers

A

Type II, III and IV fibres

26
Q

Proprioperception is sensed by

A

Muscle spindles
Golgi-tendons
Joint receptors

27
Q

Skin receptors

A

Are neuronal endings (= neuron that enters spinal cord)
Soma is always located in the dorsal root ganglion

28
Q

Receptor field

A

Area of skin covered by a single neuron. However, there is some overlap between the receptive fields of different neurons = safety mechanism

29
Q

Spatial resolution is

A

Degree of precision when detecting where we are being touched.

30
Q

Higher resolution =

A

+ neurons with smaller receptive fields (ex: in fingertips)

31
Q

Less resolution =

A

Lower nº of neurons that cover bigger receptive fields (ex: back)

32
Q

Mechanoreceptors in glabrous skin

A

Meissner corpuscles

33
Q

Mechanoreceptors in skin with hair

A

Hair follicle receptors, detect movement and direction

34
Q

Mechanoreceptors in glabrous skin and skin with hair

A

Pacinian corpuscles
Ruffini corpuscles
Merkel’s receptors (glabrous) / Tactile discs (hairy skin)

35
Q

Pacinian corpuscles - detect, location

A

Detect vibration
Located very deep in skin

36
Q

Ruffini corpuscles - detect, location

A

Detect degree of stretch of the skin over the joint
Located in joints

37
Q

Merkel’s receptors / Tactile discs detect

A

Sustained pressure

38
Q

Hair follicles and Meissner detect

A

Fast pressure

39
Q

Classification of mechanoreceptors - relation nº receptors and receptor field size

A

Large receptive field
Small receptive field

40
Q

Large receptive field mechanorecept - stimuli, receptors + nº

A

Stimuli we don’t need to precisely localize
- Vibration —> Pacinian corpuscles
- Stretch —> Ruffini corpuscles

Requires little nº of receptors

41
Q

Small receptive field mechanorecept - stimuli, receptors + nº

A

Stimuli for which we need precision
- Fast pressure —> Meisner / hair follicle receptor
- Sustained pressure —> Merkel’s receptor / Tactile discs

Requires large nº of receptors

42
Q

Classification of mechanoreceptors - speed of adaption

A

Fast adaption (phasic)
Slow adaption (tonic)

43
Q

Fast adaption (phasic) mechanoreceptors - stimuli

A

Fast pressure (Meissner)
Vibration (Pacinian corpuscles)

44
Q

Slow adaption (tonic) mechanoreceptors - stimuli

A

Sustained pressure (Merkel’s / Tactile discs)
Stretch (Ruffini corpuscles)

45
Q

Small receptive field (I), fast adapting (RA) mechanoreceptors

RA I

A

Meissner
Hair-follicle receptors

46
Q

Small receptive field (I), slow adaption (SA) mechanoreceptors

SA I

A

Merkel’s / Tactile discs

47
Q

Large receptive field (II), fast adapting (RA) mechanoreceptors

RA II

A

Pacinian corpuscles

48
Q

Large receptive field (II), slow adaptation (SA) mechanoreceptors

SA II

A

Ruffini’s corpuscles

49
Q

RA I detect

A

Superficial pressures

50
Q

SA I detect

A

Shape

51
Q

RA II detect

A

Vibration

52
Q

SA II detect

A

Stretch

53
Q

Thermoreceptors

A

Cold receptors: 5-30/34 ºC
Hot receptors: 32-45ºC (+ 45ºC = pain, burns)

Both tonic (constant Tª) and phasic (changes in Tª)

Drastic change = physically - after few seconds = firing rate normalizes

54
Q

Nociceptors (pain receptors)

A

Tª receptors —> A-delta fibers, C fibers
Mechanical stimuli —> A-delta fibers
Polymodal fibres —> C fibers
Silent (visc) receptors —> nerve endings (not pain, feel sick)

Tº + pain (+ subst) —> transient recept potential (TRP fam)

55
Q

Pain is

A

A perception, NOT A STIMULUS

Neuro (23 decks)

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