Brainscape's Knowledge GenomeTM

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


See full index

Neurology > Motor units and neurons > Flashcards

Motor units and neurons Flashcards

1
Q

What is the somatic motor system?

A

Skeletal muscle and their motor neurons (MN)

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

How many MN are found in the chain?

A

2: UMN and LMN

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

From where do LMN receive their input?

A

UMN and interneurons from somatic sensory (reflexes)

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

What NT do UMN release onto LMN?

A

Glutamate

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

Where are the somas of LMN found?

A

BS and ventral horn of SC

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

What two kinds of LMN are there?

A

alpha MN

gamma MN

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

What do aMN do?

A

Innervate muscle fibres

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

What do yMN do?

A

Innervate muscle spindles (sensory organs in muscles)

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

What do synergistic muscles do?

A

Help each other

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

What do antagonistic muscles do?

A

Oppose each other

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

What do axial muscles do?

A

Maintain posture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What do distal muscles do?

A

Move hand and feet

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

What do proximal muscles do?

A

Move limbs

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

Describe the path of a LMN

A

Exit SC in ventral root -> Spinal Nerve -> Anterior or posterior rami

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

Where do you find lots of LMN?

A

Cervical (C3-T1) and lumbar (L1-S3) enlargements.

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

What makes up a motor unit?

A

LMN and all the skeletal muscle it innervates

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

What is a MN pool?

A

All the aMN that innervate one muscle

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

How do AP generate force?

A

Each AP causes twitch which surmise to become contraction.

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

In relation to each other where are the somas of LMN innervating axial and distal muscles?

A

Axial more medial to distal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

In relation to each other where are the somas of LMN innervating flexors and extensors?

A

Flexors more dorsal to extensors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What five factors determine muscle strength?

A 
Firing rates of LMN
Number of LMN/Motor units recruited
Coordination (synergism or antagonism)
Fibre size (hypertrophy)
Fast or slow fibres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What happens at maximum AP firing on muscles?

A

Tetanus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Why do you want large (many fibres) or small (few fibres) motor units?

A

Large of strength

Small for fine movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How does MN size relate to motor unit size?

A

Small motor unit = small diameter MN

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Can motor units contain fast and slow fibres?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How do the MN innervating fast and slow fibres differ?

A

Fast- Large diameter and fast conduction.

Slow- Opposite

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How many MN innervate one muscle fibre?

A

Only 1- synapse in the middle normally

28
Q

What distinguishes if a fibre is fast or slow?

A

How quickly myosin ATPase splits ATP

29
Q

Compare slow and fast fibres

A

Slow (Type I): Red, slow and fatigue resistant. Oxidative phos generates ATP. Antigravity.
Fast (Type IIa): Red, fast and fatigue resistant. Oxidative phos generates ATP. Sustained locomotion.
Fast (Type IIb): White, fast and fatigues easily. Glycolysis generates ATP. Not in humans.
Fast (Type IIx): Very high tension and fast fatiguing. Burst power

30
Q

What does the Henneman Size Principle say?

A

The susceptibility of an α-MN to discharge action potentials is a function of its size. Smaller α-MNs (part of slow motor units) have a lower threshold than larger ones (part of fatigue resistant, or fast fatiguing, motor units).

31
Q

What is gradation of muscles?

A

Stepwise increase in force with number of motor units recruited.

32
Q

What does a fine gradation of muscles mean?

A

Small motor units therefore small increase in muscle power.

33
Q

What does coarse gradation of muscles mean?

A

Large motor units therefore large increase in muscle power

34
Q

What two kind of muscle gradation are there?

A

Fine and coarse.

35
Q

What does Henneman’s SIze Principle mean for muscle recruitment?

A

Smaller motor units are recruited first before larger ones thus allowing fine control over generation of force.

36
Q

Give the order in which LMN are recruited

A

Type I -> Type IIa -> Type IIx

37
Q

What is the myotatic reflex?

A

When a muscle is pulled it automatically pulls back (allows muscle reflex tests)

38
Q

How is change in muscle length detected?

A

Sensory organs in muscle spindle

39
Q

What is a muscle spindle?

A

Specialised muscle cell

40
Q

What 4 things make up a muscle spindle?

A

Fibrous capsule
Intrafusal muscle fibres
Sensory afferents
yMN

41
Q

How do intrafusal and extrafusal muscle fibres differ?

A

Extrafusal generate force

42
Q

Describe the myotatic reflex?

A

Stretch of muscle spindle
Activation of afferents
Activation of aMN
Contraction of muscle

43
Q

How does stretch affect AP generation of sensory afferents?

A

Increase AP rate

44
Q

How does increased AP generation from sensory afferents affect aMN firing?

A

Increase AP rate

45
Q

What can deep tendon reflexes (myotatic reflex) be used to test?

A

Spinal nerves

46
Q

Which deep tendon reflexes test which spinal nerves?

A 
Biceps (elbow)- C5/6
Supinator (wrist)- C5/6
Triceps (elbow)- C7
Quadriceps (knee)- L3/4
Gastrocnemius (ankle)- S1
47
Q

What two things make up intrafusal fibres?

A

Non-contractile equatorial region innervated by Ia afferents

Contractile ends with yMN input (soma in ventral horn)

48
Q

What role do yMN play?

A

During voluntary movement they fire along with aMN to cause contraction of intrafusal fibres in parallel to prevent them going slack thus keeping signal being transduced.

49
Q

What are the two broad categories of intrafusal fibres?

A

Nuclear bag fibres

Chain fibres

50
Q

What do chin fibres do and what innervates them?

A

Sense absolute length

Static yMN

51
Q

What two categories can nuclear bag fibres be split into?

A

Dynamic nuclear bag fibres

Static nuclear bag fibres

52
Q

What do dynamic nuclear bag fibres do and what efferents innervates them?

A

Sense rate of change

Dynamic yMN

53
Q

What do static nuclear bag fibres do and what efferents innervates them?

A

Sense absolute length

Static yMN

54
Q

What two afferent fibres innervate intrafusal fibres?

A

Aa and Ab

55
Q

Which one intrafusal fibre does Ab not innervate?

A

Dynamic nuclear bag

56
Q

What information do Aa fibres transmit?

A

Rate of change of stretch

57
Q

What info do Ab fibres transmit?

A

Absolute length

58
Q

When are static yMN recruited?

A

Most of the time but especially when muscle length change is slow and predictable

59
Q

When are dynamic yMN recruited?

A

When muscle lengths change rapidly and unpredictably.

60
Q

What are golgi tendon organs and where are they located?

A

Junction of muscles and tendons where they monitor changes in muscle length of extrafusal fibres.

61
Q

What afferents innervate golgi tendon organs?

A

Ab

62
Q

What do golgi tendon organs do?

A

Regulate muscle tension to protect from muscle overloading and keep muscle tension in optimal range.

63
Q

Where do the Ab fibres of golgi tendon organs synapse?

A

Onto inhibitory interneurons in the SC which synapse onto the aMN of their muscle.

64
Q

What reflex do the golgi tendon organs regulate?

A

Reverse myotatic reflex

65
Q

How does the reverse myotatic reflex work?

A

Golgi tendon organs fire causing activation of inhibitory interneurons which inhibit aMN to prevent muscle contraction.

66
Q

Why is the reverse myotatic reflex important?

A

In fine motor control to prevent over gripping

Neurology (30 decks)

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