What is the stimulus-response model of the nervous system?
This is a model which allows living organisms to respond to changes in their environment and act accordingly.
The senses (hearing, sight, taste etc.) allow organisms to gather information about what is happening in their environment. One a sense is stimulated, a message is sent through the central nervous system to a part of the body which will do something.
Here is an example. In the video, the runner receives a stimulus of a starter pistol going off. The sound of the gun is sensed by the ears and a message is sent by the central nervous system to the legs and arms. Muscles contract which allow the runner to explode out of the blocks.
The sound of the gun is the stimulus, the athlete starting to run is the response.
Video from: Noel Pauller