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Motor Control > Somatosensory System > Flashcards

Somatosensory System Flashcards

1
Q

What is the exception of sensory receptors of various sorts

A

Distributed throughout almost all of the tissues of the body, with nervous tissues as a notable exception

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2
Q

Somatosensory receptor

A

Any mechanoreceptors, their … or nocireceptor found embedded in the skin, fatty tissue beneath that skin, muscle tissue of musculoskeletal connective tissue (tendon, ligament or joint capsule tissue)

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3
Q

Fibre groups 1,2,3,4 and their conduction speed

A

Large myelinated 80-120m/s
Medium myelinated 35-75m/s
Small myelinated 5-30m/s
Unmyelinated 0.5-2m/s

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4
Q

Cutaneous mechanoreceptors adaptations

A

Mechanoreceptors show diff firing patterns to code duration

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5
Q

2 receptors that are slow adapting fibres

A

2 - Merkel disk receptors, Ruffini end organ

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6
Q

3 fast adapting mechanoreceptors

A

2 - Meissner corpuscle, Pacinian corpuscle, hair follicle receptor

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7
Q

Slow adapting vs fast adapting mechanoreceptors

A

Continue to fire as long as stimulus is maintained vs fall silent even when stimulus is maintained

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8
Q

Where are muscle proprioceptors abundant?

A

Skeletal muscles

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9
Q

What do muscle proprioceptors convey info regarding? 1-2

A

State of muscle

  • muslce spindles - length of muscle and velocity of stretch
  • Golgi tendon organs - changes in tension
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10
Q 
GTOs act as?
Innervated by 
Structure -2
Location 
Innervated by 
Intertwined with?
A

Golgi tendon organs act as force sensors
IB afferents - intertwined within collagen fibres of tendon
Slender encapsuled structures 0.2-1mm
Junction of muscle and tendon: in series
Ib afferent demylinated
IB afferent is intertwined with collagen fibres of tendon

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11
Q

When do intertwined Ib afferents compress?

A

In response to muscle force - Ib afferents increases AP firing frequency when muscle force increases

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12
Q

Compressed of the IB afferents

A

-

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13
Q

Increased muscle force detected by Ib afferent is through 2

A

Muscle stretch - eccentric contraction/passive stream - when its stretched, most length taken by muslce fibre (more elastic)
Muscle shortening - concentric contraction - force acts directly on tendon when muscle actively contracts - increased tension on collagen fibres compresses sensory receptors of Ib afferent

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14
Q

In what muscle force generation do you see a higher firing of IB?

A

Shortening contraction

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15
Q

2 responses to Ib afferent responses to muscle stretch.

A

Increased firing frequency upon tension increase

Sustained firing at new tension level

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16
Q

2 Ib afferent response to muslce shortening

A

Increased firing frequency upon tension release

Sustained firing at tension level

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17
Q

muscle spindle structures
location
responds to

A

encapsulated 2-10mm
parallel to extrafusal muscle fibres
stretch and velocity of muslce stretch

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18
Q

muslce spindles contain
oriented
connected to
stretch in accordance with

A

muscle fibres - intrafusal
parallel to extrafusal fibres
connected at each end to extrafusal fibres
extrafusal fibre stretch

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19
Q

3 main components of muscle spindle

A

specialized muscle fibres - intrafusal
sensory axons - Ia
motor axons - II - intrafusal fibres have capacity for contraction

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20
Q

are intrafusal muslce fibres smaller or bigger than extrafusal fibres?

A

smaller

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21
Q

two types of intrafusal fibres and how they are differenciated

A

nuclear bag and nuclear chain - organization of central nuclei - clustered bags vs in series chains

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22
Q

what are the 2 categories of nuclear bags?

A

static (BFST)

Dynamic (BFDYN)

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23
Q

how do the 2 categories of nuclear bags differ ?

A

motor innervation
sensory innervation
contractile properties

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24
Q

sensory innervation of muscle spindles - what are they innervated by? where are they?

A

Ia and II afferents
spiral around or near central region
Ia - all intrafusal fibres at central regions
II - nuclear chain and static bag only - not dynamic bag

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25
Q

effect of muscle stretch

A

intrafusal stretch which leads to spindle loading

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26
Q

Spindle loading ?

majority of length change occurs in?

A

increased AP firing frequency - elongation of afferent ending depolorizes membranes and generates AP in both sensory afferents (Ia and II)
equatorial region so more robust effect (higher firing frequency) in Ia

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27
Q

spindle unloading

A

concentric contraction - decreased firing frequency - slacking of all activity and eventually stops - dramatically diff afferent (Ia, II) firing pattern compared to stretch
The release of stretch or extrafusal shortening causes intrafusal to slacken

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28
Q

diff in response in GTO with spindle loading and unloading

A

when muslce stretches, the spindle stretches - more response in spindles, when muslce shortens - the spindles are unladed but sensory neurons in GTO increases

29
Q

AP firing during spindle unloading

A

decreases in both sensory afferents - Ia stops firing completely for a period of time until muslce returns to its normal length

30
Q

Ia firing frequency changes with?

A

muslce length

31
Q

muslce spindles are sensitive to?

A

changes in length -

32
Q

AP firing Ia and II neurons differ during …

A

static and dynamic phases of muscle length

33
Q

AP firing during static phase

A

when muscle gets stretched or released, both Ia and II afferents reach steady state firing rate that reflexts new muscle length

34
Q

AP firing during dynamic phase

A

Ia and II respond differently
Ia more robust during dynamic phase than steady state phase
II firing frequency increases slightly, but without the same vigor as Ia

35
Q

who has a greater dynamic sensitivity

A

Ia because it is more sensitive to transient changes in length

36
Q

Diff in Ia and II firing patterns is due to

A

innervation sites of these afferents, because the majority of length change happens at the equatorial region, which means most centrally located afferents (Ia) have greater opportunity for detecting length change

37
Q

what else are Ia afferents sensitive to?

A

stretch velocity - velocity sensitivity

38
Q

As velocity increases

A

Firing frequency increases - dynamic response

39
Q

steady state firing firing in Ia

A

reflects resting length

40
Q

Transient increase in Ia firing state

A

more sensitive to small length change (<0.1mm) - magnitude of transient increase in firing frequency reflects stretch velocity

41
Q

Ia encodes 3

A

static length, dynamic length, rate of length change

position, movement, and velocity of movement

42
Q

where do motor neurons innervate on intrafusal fibers?

A

polar regions - fusimotor system

43
Q

gamma motor system

A

regulate sensitivity of muslce spindles for detecting stretch

44
Q

2 types of gamma MN

A

increased steady state firing - static gamma MN

increased firing state during dynamic phase of stretch - dynamic gamma MN

45
Q

spindle efferents innervate diff types of intrafusal fibres

A

dynamic gamma MN - dynamic nuclear bag

static gamma MN - static nuclear bag and nuclear chain

46
Q

Diff gamma mn provide opportunity to differentially regulate

A

dynamic or static sensitivity of muslce spindle

47
Q

innervation of dynamic nuclear bags

A

junction of polar and central

48
Q

Region of Ia afferent

A

equatorial of all fibres

49
Q

Region of II afferent

A

near equatorial, nuclear chain and static bag only

50
Q

gamma dynamic innervates

A

dynamic nuclear bag

51
Q

gamma static innervates

A

static nuclear bag and nuclear chain

52
Q

how does CNS ensure that info regarding muscle length/rate of length change will be received during muslce contraction if muslce shortening means spindle unloading? - 3

A

activation of gamma motor neuron
fusimotor system counteracts intrafusal slackening during muslce shortening
simultaneous activation of alpha and motor MN prevents spindle from unloading during muslce shortening

53
Q

mechanistic foundation of gamma activation - what happens?

A

gamma activation leads to contraction (shortening) of polar regions which stretches the equatorial ends from both ends.

54
Q

Vallbo, 1981 - 3

A

spindle (Ia) discharge is maintained during slow concentric contractions
if gamma MN were not firing, Ia afferent would cease alpha MN
Gamma MN activited in con

55
Q

Why can gamma MN activity be adjusted independently of alpha MN activity? 2

A

CNS capable of contracting intrafusal fibres independently of extrafusal fibres
alpha gamma coactivation: MN activated synchronously

56
Q

gamma activation prior to alpha activation

A

prestretch central regions of intrafusal fibres and alter their sensitivity

57
Q

Who regulates the sensitivity of spindles to stretch

A

gamma MN

58
Q

influence of gamma MN activity known as 3

A

gamma bias
gamma gain
fusimotor set

59
Q

Prochazka, 1988 - regulation of?

How is fusimotor activity set?

A

spindle sensitivity, fusimotor activity is set according to complexity of behaviour

60
Q

Prochaska: if activity necessitates slow and predictable changes in muslce length, what MNs are activated?

A

static gamma

61
Q

Prochaska: if activity neccesitates rapid and unpredictable changes in muslce length, what MNs are activated?

A

static gamma and dynamic gamma

62
Q

Prochaka and Hulliger, 1988

A

fusimotor set theory

63
Q

activation of gamma MN increases as requirements for

A

stretch sensitivity increases

i.e. walking on ice

64
Q

CNS uses fusimotor system to

A

prime impending stretch

65
Q

Gamma bias can be adjusted by 2

A

upper motor neurons and lower neuron circuits

66
Q

to maintain constant force -

A

You can recruit fewer MU and have them fire at a higher frequency, or recruit more MUs and have them fire at a lower frequency

67
Q

receptive fields can vary in

A

size and definition

68
Q

increase of stim intensity

A

increase AP firing frequency which increases neurotransmitter output - compounded by increasing stim duration

Motor Control (9 decks)

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