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Autonomic Nervous System - Parasympathetic and Sympathetic

Compare and contrast the components of the Autonomic Nervous System (ANS)- the Sympathetic Nervous System (SNS) and the Parasympathetic Nervous System.

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The autonomic (also known as vegetative) nervous system is an extremely specialized nervous system in charge of maintaining the body's homeostasis or maintaining the necessary internal balance to sustain life (McCorry, 2007; Berntson, Sarter & Cacioppo, n.d.). It implements "an array of feedback-regulated autonomic reflexes responding to perturbations in visceral states with compensatory adjustments to restore homeostatic balance" (Berntson et al., n.d., ¶1). It comprises the parasympathetic (a.k.a. autonomic or craneal-sacral sympathetic) and sympathetic (a.k.a. thoracolumbar sympathetic) nervous systems.

Both systems have preganglonic efferent fibers that originate in the "central nervous system in connection with certain of the cranial and spinal nerves all end in ...(vegetative)... ganglia" (Grey, 2000 ¶1). From here the postganglionic afferent fibers can go to different organs.

Their differences start with the neurotransmitters. The parasympathetic system uses acetylcholine for transmissions between the afferent and efferent nerves of the system and between the efferent nerve endings and the cells or organs they innervate (Streeten, n.d.). Although the sympathetic nervous system uses acetylcholine to transmit nerve-to-nerve messages in the afferent nerves and the brain centers of the sympathetic nervous system, it uses norepinephrine to convey the messages from the sympathetic nerves to the end-organs or cells that they innervate with one important exception, the stimulus to the sweat glands is conveyed through acetylcholine (Streeten, n.d.). Another exception is the unique relation that the sympathetic system has with the adrenal medulla. The sympathetic preganglionic fibers innervate directly the adrenal medulla without a synapse releasing directly acetylcholine. In response to this stimulus, the medulla synthesizes norepinephrine and epinephrine (or adrenaline) directly to the blood stream (Bakewell, 1995).

Other basic differences between the parasympathetic and sympathetic systems are:
a) The sympathetic system has its central origin ...

Solution Summary

The solution involves a detailed discussion on the similarities and differences between the components of the anatomic nervos system, the sympathetic nervous system and the parasympathetic nervous system. It includes examples on how each one works on different organs in the body.