Stimulus: A stimulus is any event or situation that provokes a response or reaction in an organism.
Spinal Reflex Arc: This refers to the neural pathway involved in generating reflex actions. It follows a specific sequence where sensory input travels through sensory neurons, interneurons process information in the spinal cord, and motor output is sent via motor neurons.
Reaction Time: Reaction time is the interval between the presentation of a stimulus and the initiation of a response. In reflex actions, this time is generally very short, as they bypass conscious thought processes.