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MD1 Neuroscience > Reflexive and Voluntary Activation of Muscle > Flashcards

Reflexive and Voluntary Activation of Muscle Flashcards

1
Q

What are some signs of faulty motor control?

A 
Paralysis
Weaknss
Stiffness
Increased reactivity
Ticks, twitches, and jerks
Fibrillations and fasciculations
Loss of coordination and smoothness
Loss of effectiveness of movements
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2
Q

Define motor signs

A

Observable/measurable motor abnormalities/
Presence of abnormalities/
Absence of normal motor actions

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3
Q

Define motor symptoms

A

Problems of motor function reported by patients

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4
Q

Define motor syndromes

A

Associated/clustered signs and symptoms

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5
Q

Where are motor neurons found?

A

Ventral part of spinal cord

Brainstem

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6
Q

What is a motor pool?

A

Cluster of motor neurons in spinal cord innervating a muscle group

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7
Q

What are the characteristics of a motor neuron?

A

Large
Cholinergic
Fast conducting

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8
Q

Where do motor neurons synapse with muscle?

A

At neuromuscular junction (NMJ)

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9
Q

What is the ratio of motor neurons to muscle fibres?

A

1:many

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10
Q

What is a motor unit?

A

Motor neuron + all muscle fibres it innervates

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11
Q

Are motor units all the same size?

A

No

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12
Q

How much force is applied when 25% of a motor pool is activated? Why?

A

5% of force because smaller motor units recruited first

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13
Q

How is the force applied by a muscle increased?

A

Larger and larger motor units recruited

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14
Q

What kind of fibres are those that are first activated?

A

Slow - don’t fatigue over long periods of time

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15
Q

What kind of fibres are activated after slow fibres?

A

Fast fatigue-resistant

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16
Q

What kind of fibres are activated last?

A

Fast fatiguable

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17
Q

What is the neurotransmitter released at the NMJ?

A

ACh

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18
Q

What is a fibrillation?

A

Tiny contraction caused by activity of single muscle cell

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19
Q

What can fibrillations be due to?

A

Hypersensitivity

Increased AChR expression - including extra-junctional

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20
Q

What is a fasciculation?

A

Groups of muscle fibres contracting involuntarily

Can be measured on surface

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21
Q

What does long-term denervation cause?

A

Atrophy and degeneration of muscle

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22
Q

When can atrophy occur?

A

In catabolic states

  • Diabetes
  • Cushing’s disease
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23
Q

What will complete denervation lead to?

A

Progressive irreversible muscle loss

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24
Q

When at rest, are muscles inactive?

A

No, have resting tone

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25
Q

What do muscle spindles do?

A

Report back on length of muscle

26
Q

Are muscle spindles in series or parallel with muscle?

A

Parallel

27
Q

How do muscles spindles work?

A

The longer a muscle stretches > more activity in these stretch receptors

28
Q

What do Golgi tendon organs do?

A

Report back on amount of force transmitted through tendon?

29
Q

Are Golgi tendon organs in series or parallel with muscle?

A

In series

30
Q

What is the role of muscle spindles in the monosynaptic reflex?

A

Activate motor neurons of same muscle

Returns muscle to original state after stretch detected

31
Q

What are the signs of lower motor neuron lesions?

A 
Weakness/paralysis
Decreased superficial reflexes
Hypoactive deep reflexes
Decreased tone
Fasciculations and fibrillations
Severe muscle atrophy
32
Q

What are the three main types of input onto lower motor neurons?

A 
Sensory input from muscles
Secondary information from interneurons
- Most of input
Input from brain
- Come from various regions
- Most don't make direct synaptic contact but via interneurons
33
Q

What are the two groups of descending pathways in the spinal cord?

A

Lateral

Ventromedial

34
Q

What tracts are in the lateral part of the spinal cord?

A

Corticospinal tract

Rubrospinal tract

35
Q

Where does the corticospinal tract come from?

A

Cerebral cortex

36
Q

What is the corticospinal tract sometimes called?

A

Lateral corticospinal tract

37
Q

Do the corticospinal and rubrospinal tracts overlap?

A

Yes

38
Q

Where does the rubrospinal tract come from?

A

Red nucleus in brainstem

39
Q

Which tracts are in the ventromedial part of the spinal cord?

A

Tectospinal tract
Vestibulospinal tract
Pontine and medullary reticulospinal tracts

40
Q

Where does the tectospinal tract come from?

A

Superior colliculus

41
Q

What else is the tectospinal tract called?

A

Colliculospinal tract

42
Q

Where does the vestibulospinal tract come from?

A

Vestibular nuclei in brainstem

43
Q

What are the two reticulospinal tracts?

A

Pontine

Medullary

44
Q

Which reticulospinal tract is more lateral?

A

Medullary

45
Q

Where are the motor neurons for distal muscles in the ventral horns?

A

More lateral

46
Q

Why is it important that the motor neurons for distal muscles are more lateral?

A

Lateral descending tracts make most connections with lateral motor neurons > control more distal muscles
Because distal muscles involve more voluntary control

47
Q

Where are the motor neurons for proximal muscles in the ventral horns?

A

More medial

48
Q

Why is it important that the motor neurons for proximal muscles are more medial?

A

Ventromedial descending tracts make most connections with medial motor neurons > control more medial muscles
Because medial muscles involve more involuntary control

49
Q

What does corticobulbar tract refer to>

A

Cerebral inputs to motor nuclei in brainstem

Cerebral inputs to LMNs in brainstem (cranial nerves)

50
Q

Where does the corticospinal tract decussate?

A

Medullary pyramids

51
Q

How much of the descending projections from the cerebral cortex decussate at the medullary pyramids?

A

90%

52
Q

Where do the 10% of descending projections from the cerebral cortex that don’t decussate in the brainstem travel?

A

In ventromedial pathway

53
Q

Which ventromedial pathways don’t decussate?

A

Vestibulospinal tract

Reticulospinal tract

54
Q

Which ventromedial pathways decussate, and where?

A

Colliculospinal tract

Decussates immediately

55
Q

What kinds of connections do ventromedial tracts have in the spinal cord?

A

Synapse with interneurons that spread information ipsilaterally and contralaterally

56
Q

What kinds of connections do ventromedial tracts have in the spinal cord?

A

Synapse with interneurons that spread information ipsilaterally and contralaterally

57
Q

What happens when the brain can no longer influence the spinal cord?

A

Spinal locomotor circuits can’t be activated
Most of inputs from brain inhibitory > now hyper-excitable
Spinal reflex circuits become oversensitive and muscle tone above normal levels

58
Q

What is spinal shock?

A

After lesion when spinal cord doesn’t really respond
Variable
Unknown pathophysiology

59
Q

What are upper motor neuron lesion signs?

A 
Weakness
Spasticity
- Increased tone
- Hyperactive deep reflexes
- Clonus
Babinski's sign
Loss of fine voluntary movements
60
Q

What is clonus?

A

Rhythmic response to stimulus for long time after stimulus gone

MD1 Neuroscience (55 decks)

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