The Neuromuscular system 1.3

Question 1

What does the autonomic nervous system regulate?

Answer 1

It regulates the function of our internal organs such as the heart and also controls some of out skeletal muscles within the body.

Question 2

What is the movement of muscles during exercise controlled by?

Answer 2

Controlled by the brain via nerves

Question 3

What does the sympathetic nervous system do?

Answer 3

Prepares the body for exercise and is often referred to as the ‘fight or flight’

Question 4

What does the parasympathetic nervous system do?

Answer 4

Relaxes the body and slows down many high energy functions
(Has the opposite effect)

Question 5

What are the three main types of muscle fibres?

Answer 5

• Slow oxidative (type I)
• Fast oxidative (type IIa)
• Fast glycolytic (type X)

Question 6

What variation of muscle fibres do our bodies contain?

Answer 6

Our skeletal muscles contain a mixture of all three types of fibres but not in equal proportions

Relative proportion of each fibre type varies in the same muscles of different people

e.g an elite endurance runner will have a greater proprtion of slow twitch fibres in the leg muscles & in an elite sprinter- greater proportion of fast twitch fibres in leg muscles

Question 7

What are slow twitch fibres (type I) and what are their properties?

Answer 7

Have a slower contraction speed than fast twitch fibres & are better adapted to lower-intensiy exercise such as long-distance running.

They produce most of their energy aerobically

Question 8

What are fast twitch fibres (type II) and what are their properties?

Answer 8

Fibres have a mch faster contraction speed & can generate a greater force of contraction

However, fatigue v quickly & are used for short, intense burst of effort

Produce most of their enegry anaerobically

Question 9

What are the two types of fast twitch fibres (type II) and what are their properties?

Answer 9

Fast oxidative glycolytic type (IIa):
These fibres are more resistant to fatigue and are used for events such as the 1500m in athelticswhere a longer burst of energy is needed

Fast glycolytic (type x):
Fibres fatigue much quicker than type IIa and are used for highly explosive events such as the 100m sprint in athletics where a quick short burts of energy is needed

Question 10

What is the motor unit?

Answer 10

A motor neurone and its muscle fibres

Question 11

Whats the neuromuscular junction?

Answer 11

Where the motor neurone and the muscle fibre meet

Question 12

How do muscle fibres work?

Answer 12

Muscle fibres work with the nervous system so that a contraction can occur.

The motor neurone transmits the nerve impulse to the muscle fibre

Each motor neurone has branches that end in the neuromuscular junction on the muscle fibre.

Question 13

What is each muscle of motor units made up of?

Answer 13

Each muscle is made up of many motor units and they vary in size.
A small muscle that is used for fine motor control e.g muscles controlling eye movements will have motor units that only have a few fibres per motor neurone whereas large muscles such as quadraceps when leg is exended will have motor units with a motor neurone feeding hundreds of fibres

Question 14

What is the all or none law?

Answer 14

Once the motor neurone stimulates the muscle fibres, either all of them contract or none of them contract.

It is not possible for a motor unit to partially contract.

Question 15

How does the all or none law work?

Answer 15

A minimum amount of stimulation called the ‘threshold’ is required to start a contraction.

If the sequence of impulses is equal to or more than the threshold, all the muscle fibres in a motor unit will contract

However if the sequence of impulses is less than the threshold, then no muscle action will occur

Question 16

What are the three processes that help increase the strength of a contraction?

Answer 16

Wave summation
Spatial summation
Tetanic contraction

Question 17

What is wave summation?

Answer 17

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

Question 18

What is a tetanic contraction?

Answer 18

A sustained muscle contraction caused by a series of fast repeating stimuli

Question 19

What is spatial summation?

Answer 19

When the strength of a contraction changes by altering the number and size of the mucles motor units

Question 20

What is proprioceptive neuromuscular facilitation?

Answer 20

An advanced stretching technique

& considered to be one of the most effective forms of flexibility training for increasing range of motion

Question 21

What are muscle spindles & golgi tendons types of?

Answer 21

They are types of proprioceptors

Question 22

What are muscle spindles?

Answer 22

• Very sensitive proprioceptors that lie between skeletal muscle fibres
• Often called stretch receptors as they provide information to the CNS about how far & how fast a muscle is being stretched
• CNS then sends impulse back telling it to contract triggering the stretch reflex

Question 23

What are golgi tendon organs & where are they found?

Answer 23

• Found between the muscle fibre & tendon
• Detect levels of tension in a muscle

Question 24

What is autogenic inhibition?

Answer 24

• When muscle is contracted isometrically in PNF they sense the increase muscle tensions & send inhibitory signals to the brain
• Which allows the antagonist muscle to relax & lengthen