Reflexive and Voluntary Activation of Muscle Flashcards Preview

MD1 Neuroscience > Reflexive and Voluntary Activation of Muscle > Flashcards

Flashcards in Reflexive and Voluntary Activation of Muscle Deck (60):
1

What are some signs of faulty motor control?

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

2

Define motor signs

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

3

Define motor symptoms

Problems of motor function reported by patients

4

Define motor syndromes

Associated/clustered signs and symptoms

5

Where are motor neurons found?

Ventral part of spinal cord
Brainstem

6

What is a motor pool?

Cluster of motor neurons in spinal cord innervating a muscle group

7

What are the characteristics of a motor neuron?

Large
Cholinergic
Fast conducting

8

Where do motor neurons synapse with muscle?

At neuromuscular junction (NMJ)

9

What is the ratio of motor neurons to muscle fibres?

1:many

10

What is a motor unit?

Motor neuron + all muscle fibres it innervates

11

Are motor units all the same size?

No

12

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

5% of force because smaller motor units recruited first

13

How is the force applied by a muscle increased?

Larger and larger motor units recruited

14

What kind of fibres are those that are first activated?

Slow - don't fatigue over long periods of time

15

What kind of fibres are activated after slow fibres?

Fast fatigue-resistant

16

What kind of fibres are activated last?

Fast fatiguable

17

What is the neurotransmitter released at the NMJ?

ACh

18

What is a fibrillation?

Tiny contraction caused by activity of single muscle cell

19

What can fibrillations be due to?

Hypersensitivity
Increased AChR expression - including extra-junctional

20

What is a fasciculation?

Groups of muscle fibres contracting involuntarily
Can be measured on surface

21

What does long-term denervation cause?

Atrophy and degeneration of muscle

22

When can atrophy occur?

In catabolic states
- Diabetes
- Cushing's disease

23

What will complete denervation lead to?

Progressive irreversible muscle loss

24

When at rest, are muscles inactive?

No, have resting tone

25

What do muscle spindles do?

Report back on length of muscle

26

Are muscle spindles in series or parallel with muscle?

Parallel

27

How do muscles spindles work?

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

28

What do Golgi tendon organs do?

Report back on amount of force transmitted through tendon?

29

Are Golgi tendon organs in series or parallel with muscle?

In series

30

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

Activate motor neurons of same muscle
Returns muscle to original state after stretch detected

31

What are the signs of lower motor neuron lesions?

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

32

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

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

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

Lateral
Ventromedial

34

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

Corticospinal tract
Rubrospinal tract

35

Where does the corticospinal tract come from?

Cerebral cortex

36

What is the corticospinal tract sometimes called?

Lateral corticospinal tract

37

Do the corticospinal and rubrospinal tracts overlap?

Yes

38

Where does the rubrospinal tract come from?

Red nucleus in brainstem

39

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

Tectospinal tract
Vestibulospinal tract
Pontine and medullary reticulospinal tracts

40

Where does the tectospinal tract come from?

Superior colliculus

41

What else is the tectospinal tract called?

Colliculospinal tract

42

Where does the vestibulospinal tract come from?

Vestibular nuclei in brainstem

43

What are the two reticulospinal tracts?

Pontine
Medullary

44

Which reticulospinal tract is more lateral?

Medullary

45

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

More lateral

46

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

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

47

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

More medial

48

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

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

49

What does corticobulbar tract refer to>

Cerebral inputs to motor nuclei in brainstem
Cerebral inputs to LMNs in brainstem (cranial nerves)

50

Where does the corticospinal tract decussate?

Medullary pyramids

51

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

90%

52

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

In ventromedial pathway

53

Which ventromedial pathways don't decussate?

Vestibulospinal tract
Reticulospinal tract

54

Which ventromedial pathways decussate, and where?

Colliculospinal tract
Decussates immediately

55

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

Synapse with interneurons that spread information ipsilaterally and contralaterally

56

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

Synapse with interneurons that spread information ipsilaterally and contralaterally

57

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

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

What is spinal shock?

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

59

What are upper motor neuron lesion signs?

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

60

What is clonus?

Rhythmic response to stimulus for long time after stimulus gone

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