Nervous System

Question 1

Motor unit/neuron

Answer 1

Motor unit: Motor neuron and muscle fibres stimulated by its axon

Motor neuron: Nerve cell which conducts nerve impulse to group of muscle fibres

Answer 2

1. Brain detects stimulus
2. Nerve impulse is conducted down axon of motor neurone (by nerve action potential) to synaptic clef
3. Neurotransmitter is secreted in to conduct nerve impulse across gap
4. If electrical charge is above threshold, muscle fibre will contract
5. Happens in ‘all or nothing’ fashion - muscles will only contract if stimulus is above threshold

Question 3

Sympathetic/Parasympathetic

Answer 3

Sympathetic: Stimulates HR to increase
Parasympathetic: Returns HR to resting values