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KNES 251 (Motor Control) > Somatosensory System > Flashcards

Somatosensory System Flashcards

Lecture 10/11/12

1
Q

Intrafusal fibers

A

Non-force producing muscle fibers (lengthen and stretch with changes in muscle length)

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2
Q

Afferent axons

A

SENSORY INFO- innervate endings of muscle spindle and send feedback to the spinal cord

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3
Q

Muscle spindles

A

Specialized sensory receptors (provide feedback on muscle stretching to CNS)

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4
Q

Efferent axons

A

MOTOR COMMANDS- yMN’s innervate polar (contractile) ends of intrafusal fibers and send excitatory inputs from spinal cord

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5
Q

Gamma motor neuron

A

stimulates intrafusal muscle fibers

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6
Q

Sensory endings

A

sense length of intrafusal muscle fibers (part of afferent axons)

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7
Q

Center of muscle spindle

A

Non-contractile region

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8
Q

Capsule

A

connective tissue surrounding intrafusal fibers and sensory receptors that compose spindle

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9
Q

Extrafusal (skeletal muscle) fibers

A

Fibers that cause muscle contraction (parallel with intrafusal fibers)

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10
Q

Nuclear bag fibres

A

instrafusal fibres w/ nuclei arranged in a central ‘bag’ region

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11
Q

Nuclear chain fibres

A

intrafusal fibres w/ nuclei arranged along a straight chain

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12
Q

primary afferents (group 1a)

A

wrap around all types (bag/chain) types of intrafusal fibres

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13
Q

secondary afferents (group 2)

A

‘flower spray endings’ onto ONLY nuclear chain type intrafusal fibers

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14
Q

Secondary muscle spindle ending

A

Combination of a secondary afferent and the intrafusal fibres it contacts

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15
Q

Primary muscle spindle ending

A

Combination of a primary afferent and the intrafusal fibres it wraps around

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16
Q

Larger stretches of the muscle lead to…

A

Larger receptor potentials

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17
Q

Dynamic phase

A

when the muscle is being stretched

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18
Q

The difference in the firing rate of muscle spindles

A

provides the CNS with sensory input proportional to the velocity

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19
Q

Primary endings are more sensitive to…

A

the dynamic phase of movement (velocity)

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20
Q

Secondary endings are more sensitive to…

A

muscle length

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21
Q

Human microneurography

A

method of inserting an electrode directly into a peripheral nerve to record action potentials from sensory and motor neurons

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22
Q

Do secondary and primary endings respond equally as much to the dynamic phase?

A

No, primary endings are more responsive to velocity

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23
Q

Gamma motor neurons (yMN’s)

A

stimulated at the same time as the alpha-MN, the intrafusal fibers contract along with the extrafusal (skeletal) muscle fibers WHICH ALLOWSTHE MUSCLE SPINDLE TO KEEP RESPONDING DURING CONTRACTIONS

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24
Q

Without yMN

A

the spindle would stop providing feedback where your limbs are (floppy/slack fibers)

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25
Q

Co-activation

A

when alpha (extrafusal) and gamma (intrafusal) motor neurons respond together (same message from CNS)

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26
Q

Proprioception

A

our bodies understanding of where it is in space (position)

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27
Q

Kinesthesia

A

our brains understanding of movement (basically proprioception of movement)

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28
Q

Mechanotransduction

A

mechanical stimulus (energy) is converted to electrical info (voltage change) in sensory afferent neurons

29
Q

cutaneous receptive field

A

region of the skin capable of evoking action potentials in a given cutaneous afferent

30
Q

non-hairy skin

A

glabrous

31
Q

Type 1 cutaneous receptors are…

A

superficial

32
Q

Type 2 cutaneous receptors are…

A

deep

33
Q

Which receptors are slow adapting?

A

Merkel cells and Ruffini endings

34
Q

Which receptors are fast adapting?

A

Meissner’s corpuscles and pacinian corpuscles

35
Q

Place the receptors in order from most sensitive to indentation to least

A

1) Pacinian corpuscles (FA2)
2) Meissner’s corpuscles (FA1)
3) Merkel cells (SA1)
4) Ruffini endings (SA2)

36
Q

If a receptor has a low mechanical threshold what does this imply?

A

It is easily activated and sensitive to indentation (force)

37
Q

Which receptor is known for irregular discharge when stimulated?

A

Merkel cells (SA1)

38
Q

Qualities of Merkel cells (SA1)

A

-irregular discharge when stimulated
-highly sensitive to edges/curvature
-30um threshold

39
Q

Qualities of Ruffini endings (SA2)

A

-regular discharge
-very sensitive to skin stretch
-high (300um) threshold
-NOT IN NON-HUMAN PRIMATES

40
Q

Slow adapting receptors will…

A

continue to fire until stimulus is removed

41
Q

Fast adapting receptors will…

A

adapt to changes in indentation (held stimulus will stop firing)

42
Q

Qualities of Meissner’s corpuscle (FA1)

A

-codes for velocity of skin indentation (motion)
-40% of innervation in hand
-sensitive to low frequency vibration (30-50Hz)
-6um threshold

43
Q

Qualities of Pacinian corpuscle (FA2)

A

-codes for ACCELERATION (change in indentation rate/velocity)
-picks up high frequencies (50-500Hz)
-extremely low threshold (0.08um)… most sensitive to indentation

44
Q

Type 1 receptors have _______ mechanoreceptor(s)/hotspots per axon

A

multiple

45
Q

Type 2 receptors have _______ mechanoreceptor(s)/hotspots per axon

A

one

46
Q

Which type of receptor has larger receptive fields?

A

Deep (Type 2)

47
Q

Which type of receptor has a higher innervation ratio?

A

Superficial (Type 1)

48
Q

Which receptors are highest in density on the tips of fingers?

A

SA1 and FA1

49
Q

Which receptors are equally distributed?

A

SA2 and FA2

50
Q

What do merkel cells (SA1) respond most to?

A

Edges, curvature, and texture

51
Q

What do Meissner’s corpuscles (FA1) respond most to?

A

slip/motion detection, grip control

52
Q

What do Ruffini endings (SA2) respond most to?

A

skin stretch

53
Q

What do Pacinian corpuscles (FA2) respond most to?

A

feeling vibration through objects, perception of fine texture

54
Q

Vibration sensitivity

A

-receptors are very sensitive to alternating inputs
-sensitive to acceleration of skin indentation

55
Q

Spatial code

A

-CNS can determine the location of stimuli based on which afferents specifically are active

56
Q

How do thermally-gated receptors work?

A

Heat deforms the protein channel allowing ions to flow in

57
Q

When will nociceptors turn on in relation to thermoreceptors?

A

When thermoreceptors peak/asymptote

58
Q

When do nociceptors turn on?

A

become active once the heat becomes tissue damaging

59
Q

Why are spicy foods hot?

A

Capsaicin artificially creates a sensation of heat (chemical signal)

60
Q

Capsaicin

A

lipid based so it diffuses easily across cell membrane and binds inside cell (chemically igniting feeling of heat)

61
Q

What are Golgi tendon organ’s (GTO’s) attached to?

A

Tendon on one side, muscle fibres on the other

62
Q

What is one property of collagen receptors in GTO’s

A

They remain taut when stretched (crush 1b afferents)

63
Q

Is it a 1:1 ratio of muscle fibre to GTO

A

No! multiple muscle fibres attach to each GTO

64
Q

What are GTO’s helpful for detecting?

A

Active force production, not passive stretch

65
Q

On a graph, what are GTO’s similar to?

A

GTO firing closely follows EMG reading

66
Q

What are joint receptors good at detecting?

A

Extreme stretch and pressure (know ends of ROM)

67
Q

What is one fault of joint receptors?

A

Don’t give distinguishable signals (flexion/extension), not much info about angles, not great for proprioception

68
Q
A

KNES 251 (Motor Control) (13 decks)

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