Recruitment of muscle fibres Flashcards
1
Q
What needs to happen in order for a muscle to contract?
A
- Nerve impulse travels from the brain along the spinal cord to a motor neurone
- This triggers the muscle fibres attached to contract
2
Q
What is a motor unit?
A
A group of muscle fibres
3
Q
What is the all or nothing theory?
A
- Each muscle fibre within a motor unit either contracts or doesn’t contract, there is no such thing as a partial contraction
- Theory states that if a motor unit receives sufficient nerve stimulation, an action potential will be released and all the fibres in the motor unit will contract
4
Q
How do the sizes of motor units differ?
A
- In small muscles that require precise control, the motor unit is small with less muscle fibres
- Bigger muscles that require less control have more fibres within their motor units
5
Q
What are the 6 ways of varying/increasing the strength of contraction?
A
Spatial summation
Muscle fibre types
Muscle spindles
Long term memory
Wave summation
Tetanic contraction
6
Q
Describe spatial summation
A
- Varied by number and size of motor units rectuited
- Greater force of contraction = brain recruiting more and bigger motor units
7
Q
Describe muscle fibre types
A
- Fast twitch (type II) recruited
- All the structural and functional characteristics
8
Q
Describe muscle spindles
A
- Detects change in muscle length
- If stretching occurs, muscle contracts with more force by initiating the stretch reflex
- To prevent overstretching
9
Q
Describe long term memory
A
- Comparing info from past experiences can ensure correct/stronger force is applied
10
Q
Describe wave summation
A
- Increase in frequency of impulse produces a stronger contraction
- Motor unit cant relax so force increases
11
Q
Describe a tetanic contraction
A
- A sustained muscle contraction
- Caused by series of nerve stimuli that are repeated so fast that individual muscular responses are fused
- So a sustained and powerful contraction
