Nervous Control of the Muscular System - Nerve Function

Question 1

Size of a motor unit

Answer 1

The number of muscle fibres within each motor unit can vary between 1-1000+

The smaller a motor unit the more precise the action of the muscle and the lower the action potential size
e.g. The eye
The larger a motor unit, requires a larger action potential and results in the creating of gross motor skills
e.g. Kicking a ball far

The action potential size required to innervate a motor unit is proportional to the number of fibres in the motor unit.

Question 2

The all or none principle

Answer 2

When a motor unit receives stimulation/action potential that exceeds the threshold, all the muscle fibres associated with it will contract to their maximum potential

Question 3

Motor unit recruitment

Answer 3

Refers to the increasing number of motor units firing to increase the force being generated
Motor units are recruited in order depending on the intensity of the excersise

Slow twitch motor units
Have low activation levels

Higher threshold motor units (fast twitch a)
These are recruited as exercise intensity increases

Highest threshold motor units (fast twitch b)
When generating peak force the motor units that have the greatest force and threshold are recruited

Question 4

weight in proportion to motor units needed

Answer 4

The greater the weight the more motor units are required

The lighter the weight the less motor units are required

Question 5

the 2 ways to increase force produced by a muscle

Answer 5

Increasing the number of motor units recruited by increasing the stimulus size

Increasing the frequency at which impulses are sent to the motor unit resulting in the motor unit firing repeatedly to increase the force generated