What are some examples of the stimulus-response model in action?
A track and field athlete responding to the starter's pistol is an example of the stimulus-response model.
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
As blood glucose levels increase, the pancreas secretes insulin.
Responding to a stimulus and maintenance of homeostasis are both characteristics common to all living things.
A negative feedback loop means that the body usually responds to a stimulus (such as high blood sugar) by responding in a way that brings conditions back to "normal" levels. In this case, insulin production by the pancreas in healthy individuals is the body's way of controlling blood sugar levels. This is an example of the stimulus-response model.