2.85 understand that stimulation of receptors in the sense organs send electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses

When receptor in a sense organ detect a stimulus, electrical impulses are sent along sensory neurones (nerves) to the central nervous system (either to your spinal chord or an unconscious part of the brain). In the central nervous system, the sensory neurone passes the message onto the relay neurone - the gap between is called a synapse (the message is passed across the synapse with the help of chemicals). Next, relay neurones pass the message on to a motor neurone. The message will pass from a motor neurone to the effector. Lastly, the effector reacts (for example, a muscle will contract). This happens super duper quickly as they are automatic responses as you don't think about them (as they do not pass through the conscious part of your brain).

In other words, this is the reflex arc...