The parasympathetic division of the ANS operates during non-stressful situations, allowing for relaxation and energy conservation. It promotes digestion, urination, and nutrient absorption.
The preganglionic fibers of the parasympathetic division originate in the brainstem and sacral spinal cord and travel a long distance to reach to the terminal ganglia.
The terminal ganglia lie near the target organs. As a result, postganglionic fibers only travel a shorter distance to innervate the target organs.
The parasympathetic division has two major sub-divisions: the sacral and the cranial.
The sacral part consists of preganglionic fibers that begin in the sacral spinal cord, forming the pelvic splanchnic nerves.
They then travel to the pelvic plexus or the intramural ganglia, where they synapse with the postganglionic fibers.
The postganglionic fibers then transmit the parasympathetic signal to the target effectors to regulate the activities of these abdominopelvic organs.
The parasympathetic division of the autonomic nervous system (ANS) regulates rest and digestion functions in the body. It works in opposition to the sympathetic division, promoting relaxation, conservation of energy, and digestion. The parasympathetic division consists of preganglionic fibers originating from specific cranial nerves (III, VII, IX, X) and the sacral spinal nerves (S2-S4). These fibers synapse with postganglionic neurons in the terminal ganglia, innervating various organs and tissues.
The sacral part of the parasympathetic division plays a crucial role in regulating the pelvic organs' visceral functions and the large intestine's distal half It is characterized by preganglionic axons originating from the anterior roots of the second through fourth sacral spinal nerves. As these preganglionic axons travel through the sacral spinal nerves, they branch off to form pelvic splanchnic nerves. These nerves synapse with parasympathetic postganglionic neurons in the terminal ganglia present in the walls of the innervated viscera. From these terminal ganglia, parasympathetic postganglionic axons innervate the smooth muscle and glands in the walls of the colon, ureters, urinary bladder, and reproductive organs.
The parasympathetic division influences functions such as: