Muscle Recruitment

Question 1

What is a motor unit?

Answer 1

consists of motor neurone and only one type of muscle fibres

Question 2

What determines whether a motor unit produces a large or small force?

Answer 2

amount of muscle fibres and type

Question 3

What is the all or none law?

Answer 3

its not possible for a motor unit to partially contract
either all muscle fibres contract or not
a minimum amount of stimulation (threshold) is required to start contraction

Question 4

How are slow twitch and fast twitch motor units used?

Answer 4

brain recruits slow twitch motor units for low intensity exercise
if greater force of contraction is required, brain recruits fast twitch motor units

Question 5

How is the strength of contraction increased?

Answer 5

Size of motor unit
more motor units recruited
increased type IIb
increase rate of stimulation

Question 6

What is wave summation?

Answer 6

greater frequency in nerve impulses results in a more powerful contraction
next impulse begins before the last finishes so there is no time for muscle to relax and size of contraction will increase

Question 7

What is tetanic contraction

Answer 7

if impulses are fast enough, then forceful, sustained, smooth contraction will occur
calcium builds up in muscle cell from repeated nerve impulses

Question 8

What is spatial summation?

Answer 8

recruitment of further motor units in order to increase the strength of muscle contraction
motor neurones of several motor units are sent impulses at the same time, resulting in a more powerful contraction