Neuron

In the syllabus and the exam

Neuron questions focus on structure-function reasoning within the nervous system content standard, requiring candidates to link named parts of a neuron, the cell body containing the nucleus, dendrites that receive impulses, and a long axon often covered by a myelin sheath, to their roles in carrying an electrical impulse quickly and in one direction. Candidates are commonly asked to distinguish between the three types of neuron in a reflex arc, namely a sensory neuron carrying impulses from a receptor to the central nervous system, a relay neuron connecting neurons within the spinal cord or brain, and a motor neuron carrying impulses from the central nervous system to an effector, and to identify each correctly on a diagram. A recurring point of confusion is explaining the function of the myelin sheath, which candidates should describe as insulating the axon and speeding up impulse transmission, rather than describing it as generating the impulse itself. A correctly labelled neuron diagram often secures full marks in this part of the paper.

Example

A single neuron can be over a metre long in the human leg, stretching from the spinal cord to the muscles of the foot.

Related terms

SynapseReflex actionStimulus

Source:SRC-DSKP-EN