Control and coordination in mammals — practice question

A nerve is made up of bundles of different kinds of neurone. Fig. 5.1 illustrates the mean speed at which impulses are transmitted by three sensory neurone types, C, $A^\delta$ and $A^\beta$. Information given: • Impulses from pain receptors in the skin travel along sensory neurones C and $A^\delta$. • Sensory neurones C and $A^\delta$ make synapses in the spinal cord with relay neurones called projection neurones. • Projection neurones carry impulses to the region of the brain that detects pain. • Impulses from touch receptors in the skin move along sensory neurones $A^\beta$, which may also make synapses with projection neurones in the spinal cord. • Sensory neurones $A^\delta$ and $A^\beta$ have myelin. • Sensory neurones C lack myelin.