Summary

Summary

The ANS is divided into the sympathetic and para-sympathetic divisions. The sympathetic division signifies exercise, emergency, and excitement, and uses fibers that originate in the thoracic and lumbar regions of the spine. The parasympathetic division signifies digestion, defecation, and diure-sis, and uses fibers that originate in the brain and sacral spinal cord. Preganglionic fibers leave the CNS to synapse with second motor neurons to make ganglionic neurons. Axons of second neurons are called postganglionic fibers. Sympathetic and parasympathetic preganglionic fibers secrete Ach, and are therefore called cholinergic fibers. The two types of cholinergic receptors are nicotinic and muscarinic receptors. Most sympathetic postgan-glionic neurons secrete NE (noradrenalin), and are therefore called adrenergic fibers. Imbalances of the ANS and part of the PNS include hypertension, auto-nomic dysreflexia, and Raynaud’s disease. Common ­symptoms of ANS dysfunction due to aging include constipation, drying and infection of the eyes, and orthostatic hypotension.