Students should understand the relationship between the nervous and…

The idea

The neuromuscular system links nervous control to muscle action. Before exercise, motor units are recruited and muscle tone and proprioceptors prepare the body. During exercise, the brain and spinal cord increase motor unit recruitment and firing rate; more and larger motor units are activated as intensity rises, following the size principle. Muscle spindles detect stretch and trigger the stretch reflex, while Golgi tendon organs monitor tension and inhibit excessive force. During recovery, recruitment falls, firing rate decreases and the systems return toward resting state. These changes match force production to demand, so the body meets the demands of exercise at different intensities and recovers afterwards.

What earns the marks

• The nervous system controls muscle contraction through motor units and the neuromuscular junction.
• Before exercise, motor unit recruitment and proprioceptor activity prepare the body for movement.
• During exercise, increased recruitment and firing rate raise force production as intensity rises.
• Larger motor units are recruited at higher intensities, consistent with the size principle.
• Muscle spindles detect stretch and initiate the stretch reflex; Golgi tendon organs monitor tension and inhibit excessive force.
• During recovery, recruitment and firing rate decrease and the systems return toward resting levels.

Common mistakes and how to put them right

• Thinking all motor units are activated at once.

  Put it right: Recruitment increases progressively with intensity, following the size principle.

• Confusing muscle spindles with Golgi tendon organs.

  Put it right: Spindles detect stretch and trigger the stretch reflex, while Golgi tendon organs monitor tension and inhibit excessive force.

• Believing the nervous system stops controlling muscles during recovery.

  Put it right: Recruitment and firing rate decrease gradually rather than stopping abruptly.

• Assuming the neuromuscular junction is where the nerve impulse is generated.

  Put it right: It is the synapse where the motor neurone transmits to the muscle fibre.

Exam tips

• Structure answers around the three phases: prior to exercise, during exercise at differing intensities, and during recovery.
• Use precise terms such as motor unit, recruitment, firing rate, muscle spindle and Golgi tendon organ.
• Link each change to how it helps meet the demands of exercise, rather than listing changes without purpose.