The autonomic nervous system regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal. It contains three anatomically distinct divisions: sympathetic, parasympathetic and enteric. A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A reflex does not require any thought input. Peristalsis of intestine is related with autonomous nervous system whereas knee-jerk response, pupillary reflex and swallowing of food are reflex action. Related Theory The path taken by the nerve impulses in a reflex is called a reflex arc. In higher animals, most sensory neurons do not pass directly into the brain, but synapse in the spinal cord. This characteristic allows reflex actions to occur relatively quickly by activating spinal motor neurons without the delay of routing signals through the brain, although the brain will receive sensory input while the reflex action occurs. A Caution Autonomic nervous system is regulated by CNS while reflex action is controlled by spinal nerves