Answer and Explanation:
The sensory neurone is the nerve cell that links the sense organs with the central nervous system( CNS). Its receptor dendrites are located in the sense organ while the terminal dendrites are located in the CNS. The motor neurone links the CNS with the effectors such as muscle fibres. The relay neurone links the sensory with the motor neurone.
During a simple reflex action when a receptor is stimulated, it causes the generation of an impulse in a sensory neurone. The neurone conveys the impulse to the CNS where it makes synaptic connection to a relay neurone. The relay neurone connects with the motor neurone which transmits the impulse to the effectors.