The Neuromuscular System

Question 1

What is the function of the autonomic nervous system (ANS)?

Answer 1

Regulates the function of our internal organs such as the heart and controls some of our skeletal muscles within our body

Question 2

What are the 3 types of muscle fibres?

Answer 2

Type 1 - Slow oxidative (slow)
Type 2A - Fast oxidative glycolytic (fast)
Type 2B - fast glycolytic (very fast)

Question 3

What are the structural components of slow twitch muscle fibres?

Answer 3

• Lots of mitochondria
• Lots of blood capillaries
• Lots of myoglobin
• Oxidative enzymes

Question 4

What functions do slow twitch muscle fibres have?

Answer 4

• Slow twitch fibres cannot generate as much force as fast twitch fibres but…
• Produce no fatiguing by-products so…
• Can sustain low intensity exercise for prolonged periods of time

Question 5

What are the structural components of fast twitch muscle fibres?

Answer 5

• The motor neurone that carries the impulse is larger
• There are generally more type 2 muscle fibres attached to each motor neurone
• Type 2 fibres are much larger and thicker than other muscle fibres
• Few mitochondria, capillaries, myoglobin and oxidative enzymes
• Many glycolytic enzymes

Question 6

What sports may be best suited to type 2A muscle fibres?

Answer 6

400m, 200m swim

Question 7

What sports may be best suited to type 2B muscle fibres?

Answer 7

100m
Throws
Jumps

Question 8

What is the all or none law?

Answer 8

When a motor unit receives an impulse of sufficient intensity to elicit a response, all of the muscle fibres within that motor unit will contract at the same time and to the maximum possible extent. If the impulse is not of sufficient intensity, none of the muscle fibres within the motor unit will contract

Question 9

How is it possible to increase the strength of contraction?

Answer 9

• The greater the number of motor units that are recruited the stronger the contraction
• Larger motor containing more muscle fibres are recruited when a strong contraction is required
• Fast twitch motor units are recruited when a strong contraction is required, and slow twitch motor units when a low force is required

Question 10

What is wave summation?

Answer 10

• The greater the frequency of stimuli, the greater the tension developed by the muscle
• Repeated activation of a motor neurone stimulating a muscle fibre results in a greater force of contraction
• No time to relax creates a strong muscular contraction
• The most powerful contraction that can be created is called a tectonic contraction

Question 11

What is spatial summation?

Answer 11

• When a lower force is required but for a longer period of time , motor units are activated a few at a time
• This means that as one group of motor units relaxes, others are recruited, which spreads the fatigue within the muscle

Question 12

Describe the 3 stages to PNF stretching?

Answer 12

Stage 1

• The athlete is passive and a partner assists with the stretch
• Then the partner extends the body limb until the target muscle is stretched to the limit
• And tension is felt

Stage 2

• The athlete then holds the position for a few seconds then
• Contracts the stretched muscle isometrically for 5-6 seconds
• The partner must inhibit all movement

Stage 3

• The muscle group is relaxed
• Then immediately and cautiously pushed past its normal range of movement again for about 6 seconds
• Allow 30 seconds recovery before repeating the procedure 2-4 times

Question 13

What type of receptors are muscle spindles and golgi tendons?

Answer 13

Proprioceptors

Question 14

What to muscle spindles detect?

Answer 14

Changes in muscle length, they signal how far and how fast a muscle is being stretched and produce the stretch reflex

Question 15

When are the golgi tendons activated?

Answer 15

When there is tension in a muscle

Question 16

Describe the stretch reflex

Answer 16

• This is a reflex action which protects the muscle against overstretching
• When a muscle is stretched to a point at which it could become damaged, it is detected by the muscles spindles within the muscle
• The muscle spindles send a sensory impulse to the CNS, which causes a reflex shortening of the muscle, thus preventing it from over-stretching - this is the stretch reflex

Question 17

Describe golgi tendons and their function

Answer 17

• Found between muscle fibre and tendon
• Detect levels of tension in a muscle
• When a muscle has too much tension
• They send inhibitory signals to CNS
• Allows muscle to relax and lengthen
• This is autogenic inhibition