Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neurology > Motor System > Flashcards

Motor System Flashcards

1
Q

What is the difference between upper and lower motor neuron?

A

Upper - brain, supply input to LMN

Lower - soma in brainstem and ventral horn of spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Where do lower motor neurons receive input from?

A
  • UMN
  • proprioceptors
  • interneurons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the two types of lower motor neuron?

A

alpha - innervate the bulk of fibres that generate force

gamma - innervate a sensory organ (muscle spindle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

State the difference between axial, proximal and distal muscles

A

Axial - movements of the trunk
Proximal - shoulder, elbow, pelvis
Distal - hands, feet and digits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What causes the two enlargements of the spinal cord?

A

Uneven distribution of motor neurons particularly distal and proximal ones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Where are the two spinal cord enlargements?

A

Cervical - C3-T1

Lumbar - L1-S3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a motor unit?

A

All the fibres supplied by one alpha motor neuron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is a motor neuron pool?

A

A collection of alpha motor neurons that innervate a single muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Name two things force of contraction depends on

A
  • frequency of AP discharge of alpha motor neuron

- recruitment of additional synergistic motor units

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How are the LMN arranged?

A

LMN innervating axial muscles are medial to those that innervate distal muscles
Flexors are dorsal to extensors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does activation of muscle fibres depend on?

A
  • firing rate of LMNs
  • number of LMNs active
  • co-ordination of movement
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does a muscle movement arise?

A

Summation of twitches causes a sustained contraction as the number of APs increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What differentiates slow and fast fibres?

A

Differ in how quickly myosin ATPase splits ATP to provide fro cross bridge cycling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe slow type 1 fibres

A

ATP largely derived from oxidative phosphorylation, slow contraction and relaxation means it is fatigue resistant
High myoglobin - red fibres
Low tension, small alpha motor neurons, low threshold for antigravity sustained movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe type IIa fibres

A

ATP derived from oxidative phosphorylation, fast contraction and relaxation but fatigue resistant
Red and reasonably well vascularised
High tension, intermediate alpha motor neuron and threshold for sustained locomotion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe type IIb/x fibres

A

ATP derived from glycolysis, fast contraction and susceptible to fatigue
Pale and poorly vascularised
High tension, large alpha motor neurons and threshold for burst power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What type of fibre does not occur in mammals?

A

IIb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

In what order are alpha motor neurons recruited?

A

In order of size, allows fine control of muscle force across a range of tensions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Name the parts of a muscle spindle

A
  • fibrous capsule
  • intrafusal muscle fibres
  • sensory afferents (Ia fast conducting)
  • gamma motor neurons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe the monosynaptic reflex

A
  1. Stretch of muscle spindle
  2. Activation of Ia afferents
  3. Excitatory synapse in spinal cord
  4. Activation of alpha motor neuron
  5. Contraction of homoymous muscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the excitatory synapse mediated by?

A

Release of glutamate

22
Q

Which level is the biceps reflex?

A

C5-6

23
Q

Which level is the supinator reflex?

A

C5-6

24
Q

Which level is the triceps reflex?

A

C7

25
Q

Which level is the quads reflex?

A

L3-4

26
Q

Which level is the gastrocnemius reflex?

A

S1

27
Q

Describe Jendrassik Manoevre

A

Ask the patient to interlock their fingers and pull hands apart to exaggerate the patellar reflex

28
Q

Name the two parts of intrafusal muscle fibres

A
  • non-contractile equatorial region (Ia sensory neurons)

- contractile polar ends with efferent from gamma motor neurons with cell bodies in the spinal cord

29
Q

Name the two types of intrafusal muscle fibres

A

Nuclear bag fibres

Chain fibres

30
Q

Describe chain fibres

A

Sensitive to the absolute length of the muscle, innervated by static gamma motor neurons

31
Q

What are the two types of nuclear bag fibres?

A

1/dynamic

2/static

32
Q

What is the difference between dynamic and static infrafusal fibres?

A

Dynamic - very sensitive to rate of change of muscle length innervated by dynamic gamma motor neurons
Static - more sensitive to the absolute length of muscle, innervated by static gamma motor neurons

33
Q

State the two types of afferent fibres

A

Ia - form a primary annulospinal nerve ending winding around fibres
IIa - more slowly conducting, form flowerspray endings on all fibres except bag 1

34
Q

In activities where muscle length changes slowly and predictably which motor neurons are active?

A

Static gamma motor neurons

35
Q

When are dynamic gamma motor neurons active?

A

Behaviours where muscle length changes rapidly and unpredictably

36
Q

Where are golgi tendon organs found?

A

Junction of muscle and tendon

37
Q

What is the function of golgi tendon organs?

A

Monitor changes in muscle tension in series to extrafusal fibres

38
Q

What innervates golgi tendon organs?

A

Ib sensory afferents

39
Q

Why do golgi tendon organs act to regulate tension?

A
  • protect muscle from overload

- regulate tension to an optimal range

40
Q

How do group Ib afferents enter the spinal cord?

A

Inhibitory interneurons that synpase onto alpha motor neurons

41
Q

Describe the pathway of the reverse myotatic reflex

A

Tendon - Ib afferent to posterior horn
Inhibitory interneuron to anterior horn
Alpha motor neuron to muscle

42
Q

Where are proprioceptive axons found?

A

In connective tissue of joints

43
Q

What is the function of proprioceptive axons?

A

Prevent excessive flexion/extension

44
Q

What structures help with proprioception?

A
  • free nerve endings in capsule connective tissue
  • paciniform endings in periosteum near the articular attachments & fibrous joint capsule
  • Ruffini endings mainly in joint capsule
45
Q

Where do spinal interneurons receive input from?

A
  • primary sensory axons
  • descending axons from brain
  • LMN collateral branches
  • other interneurons
46
Q

What do inhibitory interneurons mediate?

A

Inverse myotatic response

Reciprocal inhibition between extensor and flexor muscles

47
Q

Describe reciprocal inhibition

A

Myotatic reflex causes the extensor muscle to contract (quads) but the antagonist flexor (hamstring) must relax simultaneously to extend the leg
Ia fibres synapse with inhibitory interneuron which synapses with antagonist muscle

48
Q

How do descending pathways contribute to reciprocal inhibition?

A

Inhibit the alpha motor neuron supplying the flexor to allow unopposed extension

49
Q

What do excitatory interneurons mediate?

A
  • the flexor reflex

- the crossed extensor reflex

50
Q

Describe the flexor reflex

A

Noxious stimulus causes limb to flex by contraction of flexor muscles and relaxation of extensor muscles

51
Q

Describe the crossed extensor reflex

A

Noxious stimulus causes limb to extend by contraction of extensor and relaxation of flexor

Neurology (29 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions