1.3 The Neuromuscular System

Question 1

What are the 3 types of muscle fibre?

Answer 1

1. Slow oxidative (type I)
2. Fast oxidative glycolytic (type IIa)
3. Fast glycolytic (type IIb)

Question 2

Sporting examples of muscle fibres?

Answer 2

slow oxidative - long distance running
fast oxidative glycolytic - sprint activities (2-4 mins)
fast glycolytic - weight lifting

Question 3

Characteristics of slow oxidative

Answer 3

• small + red
• low force and speed
• high fatigue resistance
• more mitochondria
• more energy aerobically
• minimal fibre damage
• less recovery/rest needed
• high capillary density
• small neurone size

Question 4

Characteristics of fast oxidative glycolytic

Answer 4

• red + moderate size
• medium force and speed
• fairly high fatigue resistance
• muscle fibres get damaged
• high anaerobic capacity
• fast contraction time
• large neurone size

Question 5

Characteristics of fast glycolytic

Answer 5

• large and white
• high force and speed
• low fatigue resistance
• high levels of glucose stored as glycogen
• low oxidative
• low myoglobin
• low capillary density

Question 6

Definition of a motor unit

Answer 6

a motor neurone and its muscle fibres

Question 7

How does a motor unit work?

Answer 7

• Work with nervous system so contraction can occur.
• Motor neurone transmits the nerve impulse to the muscle fibre.
• Large muscles for gross motor control will have more motor units and more fibres.

Question 8

What is the ‘all or none law’?

Answer 8

where a sequence of impulses has to be of sufficient intensity to stimulate all of the muscle fibres in a motor unit in order for them to contract. If not, then none of them contract.

Question 9

Ways to increase the strength of contraction

Answer 9

1. Wave summation
2. Spatial summation

Question 10

What is wave summation?

Answer 10

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

Question 11

What is spacial summation?

Answer 11

when the strength of a contraction changes by altering the number and size of the muscle’s motor units.

Question 12

Definition of tetanic contraction

Answer 12

a sustained muscle contraction caused by a series of fast, repeating stimuli.

Question 13

Explain PNF stretching

Answer 13

Proprioceptive neuromuscular facilitation is an advanced stretching technique. Increases range of motion. Muscle action has to be controlled in order for movement to be effective.

Question 14

What are 2 types of proprioceptors?

Answer 14

Muscle spindles
Golgi tendon organs

Question 15

Definition of muscle spindles

Answer 15

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

Question 16

Definition of Golgi tendon organs?

Answer 16

activated when there’s tension in a muscle

Question 17

Where are muscle spindles found and how do they work?

Answer 17

They lie between skeletal muscle fibres and provide information to the central nervous system about how fast/far muscle is being stretched.

The central nervous system sends an impulse back to the muscle telling it to contract. This triggers the stretch reflex (prevents over stretching + injury).

Question 18

Explain Golgi tendon organs

Answer 18

• Found between the muscle fibre and tendon, and detect levels of tension in muscles.
• When a muscle is contracted isometrically in PNF, they sense the increased muscle tension.
• Then they send inhibitory signals to the brain which allows the antagonist muscle to relax and lengthen. This is known as autogenic inhibition.