Brainscape's Knowledge GenomeTM

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


See full index

Human Physiology and Pharmacology > Week 14: Motor Units and Muscle Fibre > Flashcards

Week 14: Motor Units and Muscle Fibre Flashcards

1
Q

What is a motor unit?

A

smallest functional unit of the voluntary motor system
one alpha-motor neurone can can innovate a variable number of skeletal muscle fibres
neurone + fibres = motor unit

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

What comprises the neural element of the motor system?

A

upper motor neurone (brain)

low motor neurone (soma within brain & ventral horn of brain)

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

How is LMNs activity monitored?

A

UMNs

propioreceptors & interneurones

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

What are propioreceptors?

A

provide info about the body in space

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

What are interneurons?

A

form part of a reflex arc

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

What is the role of LMNs?

A

command muscle contraction & form the final command pathway, no intervening axon

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

What are alpha-motor neurones?

A

innervate the bulk of fibres within a muscle that generate force.

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

What are gamma motor neurones?

A

innervates a sensory organ within the muscle known as a muscle spindle

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

pairs of muscle work together in the arm?

A
  • Biceps brachii and brachialis work together as synergists.
  • Triceps brachii and anconeus are synergistic muscles
  • Oppose each other
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What pair of muscles are flexors?

A

Biceps brachii and brachialis

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

What pair of muscles are extensors?

A

Triceps brachii and anconeus

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

How do LMNs exit the spinal cord?

A

ventral roots (or via cranial nerves)

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

What is the dorsal root axon?

A

axons of sensory nerve fibres, entering cord

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

What is the ventral root axon?

A

axons of motor neurones

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

What does the ventral root join with?

A

Dorsal-root ganglion

forming a mixed spinal nerve

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

What does the mixed spinal nerve?

A

30 pairs containing sensory and motor fibres

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

What is a motor neurone pool?

A

The collection of α-MNs that innervate a single muscle

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

How is the force of muscle contraction graded? What 2 mechanism?

A
  • Frequency of action potential discharge of the α-MN

- The recruitment of additional motor units

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

Do motor units have to be coordinated?

A

YES

motor neurone pool for one bicep?

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

What distinct horn do the cell bodies LMNs have a distinct distribution of?

A

ventral (anterior) horn

21
Q

What 3 sources of input regulate alpha-MN activity?

A
  • Central terminals of dorsal root ganglion cells whose axons innervate the muscle spindles
  • UMNs in the motor cortex and brain stem
  • Spinal interneurones
22
Q

What is the axial and medial muscles?

A 
bicep= axial
tricep= distal
23
Q

What is relationship between LMNs innervating axial muscle and distal muscle?

A

LMNs innervating axial muscles medial to those innervating distal muscles

24
Q

What are the 4 types of muscle fibre contraction from least forceful to most?

A

Twitch 5Hz
Wave summation 10Hz
Unfused tetanus 20 Hz
fused tetanus 40Hz

25
Q

What 3 things does muscle strength activation depend on?

A
  • The firing rates of LMNs involved
  • The number of a LMNs that are simultaneously active
  • The co-ordination of the movement
26
Q

what 2 things does the force production by innervation muscle fibres depend on?

A
  • Fibre size (hypertrophy)

- Fibre phenotype (“fast” or “slow” contracting muscle)

27
Q

Can the number of fibres a motor unit stimulates be different eh between X and Y?

A

YES
e.g. X motor neurone effects 5 fibres (smaller tension)
Y motor neurone effects 9 fibres (tension greater)

28
Q

What is the different effects of small and large muscle fibres?

A
  • Small (few fibres) for fine. movements e.g. eye muscles

- Large(hundreds to thousands of fibres) in large postural (antigravity) muscles e.g. leg muscles

29
Q

What is the difference in size between small alpha-MNs?

A

Small motor units are innervated by small α-MNs (soma diameter) whereas the converse is true for large motor units

30
Q

What is the features of a aplha-MNs innervating fast type muscle fibres?

A

tend to be larger and have faster conducting axons than those of slow units

31
Q

Can a muscle type be both fast and slow type?

A

NO

32
Q

How many motor axons innervate a single muscle fibre?

A
  • Each muscle fibre is innervated by a single motor at the endplate
  • Some extraocular muscle fibres have multiple endplates)
33
Q

What myosin heavy chains do slow oxidative and Fast fibres have?

A

slow: Type 1
fast: Type 2

34
Q

How is the ATP of slow oxidative formed?

A

oxidative phosphorylation

35
Q

How quickly is the conytraction and relaxation of Type 1 fibres?

A

SLOW

36
Q

What skeletal muscle fibres are fatigue resistant?

A 
Slow oxidative (Type 1)
Fast (Type iia)
37
Q

How is ATP of fast type muscle fibres produced?

A

oxidative phosphorylation.

38
Q

How quickly is the contraction and relaxation of Type iia fibres?

A

FAST

39
Q

What are the 2 types of fast type skeletal muscle fibres?

A

type iia

type iix

40
Q

Why is slow oxidative fibres dark in colour?

A

high myoglobin content

41
Q

How well vascularised are Type iia skeletal muscle fibres?

A

reasonably well vascularised

42
Q

Where is the ATP from type iix skeletal muscle fibre derived from?

A

glycolysis

43
Q

How well vascularised is Type IIx?

A

poorly vascularised

44
Q

How fast is type iia & iix contraction?

A

FAST

45
Q

Is Type iix fatigue resistant?

A

NO

46
Q

What fast skeletal muscle type is not present in mammals?

A

Type iib

47
Q

What motor units are most easily activated & trained by any muscle that activates the muscle?

A

slow motor units

48
Q

What order are alpha-MNs recruited?

A

by size allows dine and graded development of muscle

wider range of tensions developed

49
Q

What type of skeletal muscle fibre is recruited. first?

A

type 1 the iia then iix

Human Physiology and Pharmacology (31 decks)

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