Stimulus-response pathway

A stimulus-response pathway describes how an organism responds to a stimulus from the environment or from within its own body. It always begins with a stimulus: a change that can be detected by a sensory organ. An adequate stimulus is the type of stimulus for which a sensory organ is especially specialized. The eye responds primarily to light, the ear to sound and the nose to odorants. The sensory organ detects the stimulus and converts it into information that can be transmitted through the nervous system.

This information travels through afferent nerves to the brain, or central nervous system. “Afferent” means that information is conducted from a sensory organ toward the central nervous system. In the brain, incoming information is consciously processed, compared with existing knowledge and interpreted. Only then is an appropriate response selected. In this model, the brain or CNS is therefore the site of conscious processing and control.

The brain then sends a command through efferent nerves to an effector. “Efferent” means that information travels away from the central nervous system toward an organ that carries out an action. An effector is the organ that actually produces the response, for example a muscle. The observable response is the final result of this control process.