What is the first step in the reflex arc?

The first step in the reflex arc is when the stimulus is received by the receptor. This initial phase is crucial because it signals the beginning of the reflex action. Receptors are specialized cells or structures that detect changes in the environment, known as stimuli, such as heat, pressure, or pain. When a stimulus is detected, it generates an electrical impulse in the receptor.

This impulse is then transmitted through sensory neurons towards the central nervous system, where it is processed. The entire reflex arc is designed to facilitate an immediate response to harmful situations, bypassing higher brain functions for quicker action to protect the body, which emphasizes the importance of the receptor's role in initiating the process. Understanding this basic mechanism is essential in studying how reflexes function in both human and animal physiology.