Output through motor neurons links named stimuli, coordinating structures and effectors so body systems or plant tissues produce an integrated biological response.
Coverage 2015–2015 · Updated 16 Jul 2026
Motor neurones turn CNS decisions into muscle action.
Motor neurones carry action potentials from the CNS to an effector. At a neuromuscular junction, acetylcholine depolarises the muscle membrane and starts the calcium-controlled contraction sequence.
CNS signal → motor axon → acetylcholine release → muscle action potential → calcium release.
An impulse at a motor end plate opens ion channels; the resulting muscle action potential travels along the fibre and triggers calcium release from the sarcoplasmic reticulum.
The motor neurone does not contract the muscle directly; transmitter and membrane events link the two cells.
This objective is assessed through multiple choice, commonly using Describe / Identify.
Describe / Identify
Mark schemes reward named structures, correct direction of information flow and explanations that keep the sequence causal.
Giving a general body-system answer without the specific pathway step for motor neuron output pathway.
Representative question
What is the main role of nerves in human movement?
To cause muscles to stretch
To move joints
To transport pain signals that indicate muscle injuries
To stimulate muscle contraction
