1. Key Definitions

· Stimulus refers to a change in the environment.

· Receptors (root word: receive) on sense organs detects stimulus and generates nerve impulses that are sent to the nervous system. Examples include temperature receptors, stretch receptors, olfactory receptors

· Effectors generate a response upon receiving nerve impulses.

Receptor detects a stimulus and sends nerve impulse (electrical signals) to the Central Nervous System (CNS). A nerve impulse is then sent to the effector to respond to the stimulus.