Explain the pathway of a reflex, and name the neurones involved.

(Background) A reflex is a sudden, unconscious and involuntary response to a stimuli. It occurs through 3 different types of neurones or nerve cells: 1) The stimulus (heat, pain, light) is detected through a receptor in the organ that has received the stimuli. (skin, eye)2) The receptor feeds into a sensory neurone (also called an afferent neurone) which runs from the organ that has been affected to the spinal cord. 3) Here the sensory neurone synapses (connects) with the relay neurone, which runs this signal through the spinal cord and synapses to a motor neurone. 4) The motor neurone runs from the CNS to the effector organ (usually a muscle) allowing for a muscle contraction and therefore a movement in response to the stimulus (e.g. to move away from the painful hot stove).