Neuromuscular System

Question 1

What are the three muscle fibre types?

Answer 1

slow twitch- type 1a
fast twitch- type 2a
fast twitch- type 2b

Question 2

What are the characteristics of type 1a fibres?

Answer 2

functional- contract slowly

• produce a small amount of power (dont fatigue quickly)
• aerobically powered
• good for long endurance events

structural- red due to lots of rbc
-high myoglobin and mitochondria count

Question 3

What are the characteristics of type 2a fibres?

Answer 3

functional- contract quickly with power

• anaerobically powered with small % of O2
• fatigue quickly
• good for prolonged speed events

structural- pink due to limited number of rbc
-fewer myoglobin and mitochondria

Question 4

What are the characteristics of type 2b fibres?

Answer 4

functional- contract quickest with most power

• anaerobically powered
• fatigue very quickly
• good for fast/explosive events

structural- minimal O2 supply (ATP/PC system)

• white as they have no rbc
• contain no myoglobin or mitochondria

Question 5

What can training do to muscle fibre types?

Answer 5

you cannot change slow twitch fibres to be fast
number of slow/fast twitch is genetic
you can increase the size of muscle fibres through training- hypertrophy

Question 6

What is a motor unit?

Answer 6

a motor neurone and its muscle fibres

Question 7

What is a motor neurone?

Answer 7

nerve cells which transmit the brain instructions as electrical impulses to the muscles
each motor neurone has branches that end in the neuromuscular junction

Question 8

What are muscles made up of?

Answer 8

made up of many motor units
small muscle used for finer motor control have few fibres per motor neurone
large muscles used for gross motor control have a motor neurone that feeds hundreds of fibres

Question 9

What is the all or none law?

Answer 9

either all of the muscle fibres in a motor neurone contract or none of them do
there is no variation in the strength of a motor unit- it either contracts or it doesn’t
if the sequence of impulses is less than the threshold then the muscle fibres in the motor unit will not contract

Question 10

What is spatial summation?

Answer 10

the strength of contraction changes as all motor units are recruited but for a short time and are activated at different times so the contraction and relaxation are spread out
rotation system where some units contract whilst others rest and continuously contract
(no. of units recruited increased)

Question 11

What is wave summation?

Answer 11

repeated activation of a motor neurone stimulating the muscles with no rest as the impulse is sent before the previous one is finished which results in a greater force of contraction
(frequency of impulse increased)