A reflex arc is a neural pathway that controls reflexes, which are instantaneous responses to stimuli without thinking. It is the shortest pathway for an impulse to travel from the receptor organ via the central nervous system to the effector. The reflex arc includes a receptor, a sensory neuron, a motor neuron, the brain and spinal cord, and an effector. The components of a reflex arc are as follows:

• Stimulus: The event that triggers the reflex.

• Receptor: The sensory organ that detects the stimulus and sends a signal to the central nervous system.

• Sensory neuron: The neuron that carries the signal from the receptor to the central nervous system.

• Brain or spinal cord: The central nervous system processes the signal and sends a response.

• Motor neuron: The neuron that carries the response from the central nervous system to the effector.

• Effector: The muscle or gland that produces the response.

The reflex arc is a sort of neural circuit that starts with a sensory neuron at a receptor and finishes with a motor neuron at an effector. Most sensory neurons in vertebrates synapse in the spinal cord rather than passing directly into the brain. This enables faster reflex actions by engaging spinal motor neurons without having to wait for messages to go to the brain.