Neuromuscular

Slow- type 1 slow oxidative muscle fibres a01/2/3

Slow Oxidative Fibres (Type I)

AO1 (knowledge)

1. Contract slowly.

2. Resistant to fatigue.

3. Mainly use aerobic respiration.

4. Have high numbers of mitochondria.

5. Contain large amounts of myoglobin and capillaries.

AO2 (application)

1. A marathon runner uses slow oxidative fibres during long-distance running.

2. A footballer jogging back into position uses Type I fibres.

3. Cyclists in endurance races rely heavily on slow oxidative fibres.

AO3 (analysis/evaluation)

1. Because they resist fatigue, performers can maintain performance for longer periods.

2. However, slow contraction speed means they are less effective for explosive movements.

3. This makes them more suitable for endurance events than sprint events.

Fast type IIa fast oxidative glycolic (30-60 secs)

1. Contract faster than slow oxidative fibres.

2. Can use both aerobic and anaerobic energy systems.

3. Moderately resistant to fatigue.

4. Produce greater force than Type I fibres.

5. Suitable for repeated high-intensity activity.

AO2 (application)

1. A midfielder repeatedly sprinting and recovering uses Type IIa fibres.

2. An 800m runner relies on fast oxidative glycolytic fibres.

3. A boxer throwing repeated combinations uses Type IIa fibres.

AO3 (analysis/evaluation)

1. Their ability to work aerobically and anaerobically makes them versatile in many sports.

2. They allow performers to repeatedly produce force without fatiguing too quickly.

3. However, they still fatigue faster than Type I fibres during prolonged exercise.

Fast type IIx fast glycotic

AO1 (knowledge)

1. Contract very quickly.

2. Produce large amounts of force.

3. Mainly use anaerobic respiration.

4. Fatigue rapidly.

5. Have fewer mitochondria and capillaries than Type I fibres.

AO2 (application)

1. A 100m sprinter explosively leaving the blocks uses fast glycolytic fibres.

2. A shot putter relies on Type IIx fibres during the throw.

3. A footballer jumping for a powerful header uses fast glycolytic fibres.

AO3 (analysis/evaluation)

1. Their high force production improves explosive performance.

2. Rapid fatigue means they are unsuitable for endurance activities.

3. This makes them most effective in short-duration, high-intensity events.

Slow twitch and energy systems.

Aerobic

1mol of glucose=enough energy to re synthesise 38 atp 1:38

ATP slow to re synthesise but these fibres are more endurance based so less likely to fatigue

Fast twitch type 2a/x energy systems

Anaerobic glycolysis-2a

ATP PC-2x

2x- 1ATP re synthesised per molecule

2 ATP per mol glucose-2a

Very fast but can’t last for long as these fibres have least resistance to muscle fatigue

Motor units

Is the motor neurone and number of fibres it stimulates

1 motor neurone stimulates all the fibres in a motor unit

Only 1 type of muscle fibre contained within 1 unit

Can vary in size containing diff number of muscle fibres

Muscle stimulation and contraction

An impulse is sent down the motor neurone where it arrives at a neuromuscular junction. It is here where a series of chemical reactions take place causing the muscle fibres to contract. When the nervous stimulation stops the muscle relaxes.

The impulse received at the muscle needs to meet a minimum threshold in order to cause the muscle fibres to contract, If the threshold is not met. the muscle will not contract, This is called

the all or none law

Spatial summation (summary till reach threshold)

When a neurone wants to send a signal to a motor unit to make it contract, it receives impulses from other neurones.

One single impulse might not be strong enough to trigger this.

Spatial summation is when a neurone receives multiple impulses from different neurones at the same time. When they arrive at the same time, they add up - Summate. This makes the signal strong enough and triggers the neurone to send its own impulse to the muscle - an action potential is Released.

All or none law. Asked about varying strength of contraction always link to this

There is a minimum stimulation (threshold) needed to start a contraction.

• The impulse must be equal to or greater than the threshold.

• When the threshold is reached, ALL the muscle fibres in the motor unit contract

• If the threshold is not reached, NONE of the fibres in the motor unit contracts

Varying the strength of muscle contraction

Wave summation frequent stimulation of motor units

When a large force is needed, the motor units are stimulated frequently which means that once the motor unit is stimulated it is not given time to return to resting state before it is stimulated again.

Therefore, it produces a greater force.

• This can produce what is known as a tetanic contraction -this is the most powerful contraction that can be produced.

Proprioceptors & Control of Muscle Contraction

Muscle Spindle Apparatus

The muscle spindle apparatus are proprioceptors that detect changes in the length of the muscle.

• If a muscle lengthens quickly it is detected by

muscle spindle apparatus

• They send a message down a sensory nerve to the CNS

• Message comes back down a motor nerve to the

muscle and muscle contracts – this is called the

stretch reflex.

• Prevent overstretching of muscle and injury

Golgi Tendon organs

Golgi tendon organs are proprioceptors that are located in the tendons of the muscle where they join

to the bone. When the muscle shortens the golgi tendon organs lengthen.

• When muscles shorten the increase in tension is

detected by the golgi tendon organs

• If there is too much tension in a muscle the golgi

tendon organs detect it

• They send a message down a sensory nerve to the CNS.

• The muscle then relaxes to reduce muscle tension.

• This is called autogenic inhibition

Proprioceptive Neuromuscular Facilitation (PNF)

PNF is a passive and partner assisted method of stretching, used to improve

flexibility. Its main aim is to override the stretch reflex.

Stage 1

Partner stretches the target

muscle to its full range of motion

• Muscle spindle apparatus lengthens and detects the stretch, sends a signal to CNS to Initiate the stretch reflex, designed to prevent injury and overstretching.

Stage 2

Contract the muscle group

isometrically for 5-6 seconds

Relax & partner prevents any

movement

• Golgi tendon organs detect the tension

created in the muscle. This:

• Overrides the stretch reflex as the muscle spindles shorten slightly

• Causes autogenic inhibition and the muscle relaxes

Stage 3

Stretch the target muscle again,

taking it further through your range

of motion and hold for 6 seconds

Allow 30 seconds recovery before

repeating 2-4 times

• The muscle can be stretched further through Its range of motion than the initial stretch