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