neuromuscular system

Question 1

aerobic

Answer 1

• ‘with oxygen’
• refers to exercise that is low to medium intensity where the oxygen demand of muscles is met

Question 2

anaerobic

Answer 2

• ‘without oxygen’
• refers to energy as high intensity where the demand for oxygen by the muscles is so high it cannot be met.

Question 3

hypertrophy

Answer 3

where the muscle has become bigger and stronger

Question 4

motor unit

Answer 4

a motor neurone and its muscle fibres

Question 5

motor neurones

Answer 5

nerve cells which transmit the brains instructions as electrical impulses to the muscles

Question 6

neuromuscular junction

Answer 6

where the motor neurone and the muscle fibre meet

Question 7

all or none law

Answer 7

where the sequence of impulses has to be of sufficient intensity to stimulate all of the muscle fibres in a motor unit for them to contract
- if not none of them contract

Question 8

wave summation

Answer 8

where there is a repeated nerve impulse with no time to relax so a smooth sustained contraction occurs, rather than twitches - a tetanic contraction

Question 9

tetanic contraction

Answer 9

a sustained muscle contraction cause led by a series of fast repeating stimuli during wave summation

Question 10

spatial summation

Answer 10

• when the strength of a contraction change by altering the number and size of the muscles motor units
• the activation of these motor units is staggered, enabling a sustained contraction to be maintained as some motor units are contracting while others are relaxing, delaying fatigue

Question 11

muscle spindles

Answer 11

these detect how far and how fast a muscle is being stretched and produce the stretch reflex

Question 12

golgi tendon organs

Answer 12

these are activated when there is tension in a muscle

Question 13

isometric contraction

Answer 13

where there is tension in a muscle but no visible movement

Question 14

autogenic inhibition

Answer 14

where there is a sudden relaxation of the muscles in response to high tension
- the receptors involved in this process are Golgi tendon organs

Question 15

role of the sympathetic and parasympathetic nervous systems

Answer 15

transmit information from the brain to the parts of the body that need to adjust what they are doing to prepare for exercise

Question 16

role of sympathetic system

Answer 16

• prepares the body for exercise
• fight or flight

Question 17

role of parasympathetic system

Answer 17

• relaxes the body and slows down many high-energy functions
• rest and digest’

Question 18

slow twitch fibres (type 1)

Answer 18

• slower contraction speed than fast fibres and are better adapted to lower intensity exercise such as long-distance running
• they produce most of their ATP aerobically and have specific characteristics that allow them to use oxygen more effectively

Question 19

fast twitch fibres (type 2)

Answer 19

• fast contraction speed and can generate a greater force of contraction
• fatigue quickly and are used for short, intense bursts of effort
• produce energy anaerobically

Question 20

type 2a fibres

Answer 20

• more resistant to fatigue and are used for events such as the 800m in athletics where a longer burst of energy is needed

Question 21

type 2x fibres

Answer 21

• fatigue very quickly and are used for highly explosive events e.g. 100m in athletics where a quick, short burst of energy is needed

Question 22

characteristics of slow twitch (type 1) fibres

Answer 22

Contraction speed: slow
Motor neurone size: small
Force produced: low
Fatigability: low
Mitochondrial density: high
Myoglobin content: high
Capillary density: high
Aerobic capacity: very high
Anaerobic capacity: low

Question 23

characteristics of fast twitch (type 2a) fibres

Answer 23

Contraction speed: fast
Motor neurone size: large
Force produced: high
Fatigability: medium
Mitochondrial density: medium
Myoglobin content: medium
Capillary density: medium
Aerobic capacity: medium
Anaerobic capacity: high

Question 24

characteristics of fast twitch (type 2x) fibres

Answer 24

Contraction speed: fast
Motor neurone size: large
Force produced: high
Fatigability: high
Mitochondrial density: low
Myoglobin content: low
Capillary density: low
Aerobic capacity: low
Anaerobic capacity: very high

Question 25

functional characteristics of muscle fibres

Answer 25

- contraction speed - force produced - fatigability - aerobic capacity - anaerobic capacity

Question 26

structural characteristics of muscle fibres

Answer 26

- motor neurone size. - mitochondrial density. - myoglobin content. - capillary density.

Question 27

how to increase the strength of a contraction

Answer 27

- wave summation - spatial summation

Question 28

what are muscle spindles and golgi tendon organs types of?

Answer 28

proprioceptors

Question 29

role of muscle spindles in PNF

Answer 29

- sensitive proprioceptors that lie between skeletal muscle fibres - they provide excitory signals to the central nervous system about how fast and how far a muscle is being stretched - the central nervous system then sends an impulse back to the muscle telling it to contract, which triggers the stretch reflex, causing it to contract to prevent overstretching, reducing the risk of injury

Question 30

role of golgi tendon organs in PNF

Answer 30

- found between the muscle fibre and tendon, they detect levels of tension - then the muscle is contracted isometrically, they sense an increase in muscle tension and send inhibitory signals to the brain, which allows the antagonist muscle to relax and lengthen, known as autogenic inhibition

Question 31

3 stages of PNF stretching

Answer 31

Individual performs passive stretch with help of partner and extends leg until tension is felt. Stretch detected by the muscle spindles and excitory signals cause a stretch reflex should occur if stretched too far. Then isometrically contracts the muscle for 10 seconds by pushing leg against partner who supplies resistance. Golgi tendons activated due to tension and the inhibitory signals they send override the excitory signals from the muscle spindles, delaying the stretch reflex. When leg is passively stretched again, the golgi tendon organs are responsible for the antagonist muscle relaxing, which means the leg stretches further. Can be repeated until no more gains are possible.

Question 32

stage 1 of pnf stretching

Answer 32

- individual performs passive stretch with help of partner and extends leg until tension is felt - stretch detected by the muscle spindles and excitory signals cause a stretch reflex should occur if stretched too far

Question 33

stage 2 of pnf stretching

Answer 33

- then isometrically contracts the muscle for 10 seconds by pushing leg against partner who supplies resistance - golgi tendons activated due to tension and the inhibitory signals they send override the excitory signals from the muscle spindles, delaying the stretch reflex

Question 34

stage 3 of pnf stretching

Answer 34

- when leg is passively stretched again, the golgi tendon organs are responsible for the antagonist muscle relaxing, which means the leg stretches further - can be repeated until no more gains are possible

Question 35

The training that elite performers undertake may include proprioceptive neuromuscular facilitation (PNF) stretching. Explain the role of the muscle spindles and golgi tendon organs in PNF stretching. (3)

Answer 35

- golgi tendons detect a stretch in the muscles - the muscles then relax because of an inhibited stretch reflex - this is designed to prevent injury - allows a greater range of movement

Question 36

Contraction of different types of muscle fibres involves the use of motor units. What do you understand by the term 'motor unit'? (2)

Answer 36

- made up of a motor neurone and muscle fibres - all fibres are fast or slow twitch within that motor unit - the sequence of impulses has to be of sufficient intensity to stimulate all of the muscle fibres in a motor unit for them to contract - if not none of them contract

Question 37

How are motor units involved in the process of spatial summation? (2)

Answer 37

- motor units cause an increase in the strength of contraction - using bigger units and more motor units will increase the strength of the contraction - fast-twitch units produce more force than slow-twitch units

Question 38

describe the characteristics of the main muscle fibre type used by marathon runners. (4)

Answer 38

- slow oxidative fibre/type 1 - slow motor neurone conduction capacity - high numbers of mitochondria - high myoglobin content - high capillary density - less powerful

Question 39

The training that elite performers undertake may include PNF stretching. Explain the role of the muscle spindle apparatus and golgi tendons during PNF stretching. (5)

Answer 39

* Muscle spindles detect changes in muscle (fibres) * Cause stretch reflex * Designed to prevent overstretching/protective * Aim of PNF to override the stretch reflex * Golgi tendon organs/GTO activated/detect overstretching of muscles * Causes the muscles to relax/autogenic inhibition * Allows greater range of movement than the initial stretch/greater range of movement

Question 40

Describe the structural characteristics of the main muscle fibre type used by a triathlete. (4)

Answer 40

* Slow twitch fibres/type I * Small motor neurone size * High mitochondrial density * High myoglobin content * Large capillary density