neuromuscular system and PNF 1.3

Question 1

What is the other name for type 1 (slow twitch) muscle fibres?

Answer 1

slow oxidative muscle fibres

Question 2

characteristics of type 1 muscle fibres

Answer 2

• have a slower contraction speed
• have a high aerobic capacity due to high mitochondrial density, high myoglobin content, and high capillary density
• low fatiguability
• low anaerobic capacity
• low force produced due to small motor neurone size

Question 3

what is another name for type 2a muscle fibres

Answer 3

Fast oxidative glycolytic muscle fibres

Question 4

characteristics of type 2a muscle fibres

Answer 4

• large motor neurone six=ze causing a large force produced from contraction
• high anaerobic capacity
• medium aerobic capacity (medium fatiguability) due to medium myoglobin content, medium mitochondrial density, medium capillary density

Question 5

what is another name for type 2b muscle fibres?

Answer 5

fast glycolytic muscle fibres

Question 6

characteristics of type 2b muscle fibres

Answer 6

• large motor neurone size = large force production
• very high anaerobic capacity
• low aerobic capacity: low mitochondrial density, low myoglobin content, low capillary density
• high fatiguability

Question 7

what is the effect of training on fibre type

Answer 7

• fibre type tends to be genetically determined
• training can increase size of muscle fibres (hypertrophy) resulting in greater strength

Question 8

what is a motor unit?

Answer 8

consists of a motor neurone and it’s muscle fibres
- only one type of muscle fibre can be found in one particular motor unit

Question 9

function of motor neurone

Answer 9

transmits the nerve impulse to the muscle fibre so that a contraction can occur

Question 10

what is the neuromuscular junction

Answer 10

where the motor neurone and muscle fibre meet

Question 11

what is the all or none law?

Answer 11

• once the nerve impulse stimulates the muscle fibres, either all of them contract or none of them do (it isn’t possible for a motor unit to partially contract0
• minimum amount of stimulation is required to start a contraction. If sequence of impulses is less than the threshold, no muscle contraction will occur.

Question 12

what is wave summation and how does it control the strength of a contraction?

Answer 12

the greater the frequency of the stimuli, the greater the tension developed by the muscle (greater force of contraction)

Question 13

how does spatial summation control the duration of a contraction?

Answer 13

It involves recruiting motor units whilst others rest and then swapping allowing a longer contraction. e.g. helpful for a climber holding onto the wall

Question 14

how does spatial summation control the strength of a contraction?

Answer 14

• the correct number and size of motor units are selected.
• e.g. a strong contraction would involve recruiting large numbers of large motor neurones (type 2b)

Question 15

what does PNF stand for?

Answer 15

Proprioceptive neuromuscular facilitation

Question 16

what is PNF?

Answer 16

an advanced stretching technique used to increase the range of motion at a joint

Question 17

function of muscle spindles

Answer 17

• they detect how far and how fast the antagonist is being stretched by sending impulses to the CNS. They will initiate a stretch reflex/contraction by the CNS sending impulses back to the muscles when they detect overstretching. This prevents overstretching which can cause injury
• found between muscle fibres

Question 18

function of Golgi tendon organs

Answer 18

• found between the muscle fibre and tendon
• detect increased tension in the muscle when the antagonist isometrically contracts and will autogenic inhibition. This is a sudden relaxation of the antagonist.

Question 19

advantages of PNF

Answer 19

• increased range of motion at a joint
• increased muscle strength
• increased muscle flexibility

Question 20

disadvantages of PNF

Answer 20

• high risk of injury
• requires a partner and good communication
• not suitable for younger athletes

Question 21

explain the CRAC method of PNF

Answer 21

• a passive stretch occurs and muscle spindles detect how far and fast the muscle is being stretched by sending impulses to the CNS
• the stretch is done until tension is felt, which will occur if the muscle is overstretched due to CNS sending impulses back to muscle causing a contraction to prevent overstretching
• antagonist then isometrically contracts in response to impulse
• Golgi tendon organs detect this contraction and initiate autogenic inhibition. This is a sudden relaxation of the antagonist in response to high amounts of tension. Finally the agonist contracts and the joint is able to move further