Stimulus

In the syllabus and the exam

Stimulus is the entry point of both the nervous and hormonal coordination content standards, and candidates are expected to identify the specific stimulus in a described scenario and trace it through detection by a named receptor to a specific response, rather than treating a stimulus as a vague, generic idea. In plant-based questions, a stimulus such as unidirectional light or gravity is linked to a tropic response through the action of auxin, while in animal-based questions a stimulus such as a change in temperature, light intensity, or a painful touch is linked to a receptor, a coordination pathway, and an effector's response. A common exam format presents a short set of scenarios and asks candidates to identify the stimulus, the receptor involved, and the resulting response for each, testing whether the three ideas are clearly separated in the candidate's mind. A frequent error is naming the response itself when asked to identify the stimulus, for example describing the plant bending rather than naming unidirectional light as the stimulus.

Example

A sudden bright light shone into the eye is a stimulus that causes the pupil to constrict as a protective response.

Related terms

NeuronHormoneReflex action

Source:SRC-DSKP-EN