Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 14 - The Autonomic Nervous System - Review Questions - Page 542: 6


The autonomic nervous system(ANS) comprises two divisions; 1. the sympathetic branch and 2, the parasympathetic branch Most visceral organs are innervated by both sympathetic and parasympathetic fibers. These organs include the heart and blood vessels, the organs of the respiratory system, organs of the GI and GU ur systems some glands and some sense organs. The effects of sympathetic and parasympathetic stimulation are usually antagonistic: thus wile sympathetic stimulation increases heart rate, dilates bronchioles, and decreases gastric motility, parasympathetic simulation has the opposite effects on these visceral organs. Ordinarily, one is not aware of ANS initiation and and maintenance and adjustment of the activities of visceral organs. That is to say this branch of the nervous system is not under minute to minute conscious control. Therefore, it is appropriate to refer to it as an involuntary system, This does not mean that there are never any CNS influences on ANS activities. Some common human emotions are fear , anger, sadness, disappointment, shame, sadness, Joy, love and surprise. . In addition to skeletal muscle activities that these eeactions may prompt there are usual visceral organ reactions to fear,shame, anger, surprise, joy, and sadness. Some of these emotions may be accompanied by increase in heart rate, increase in blood pressure , shunting of blood in the cardiovascular system, increased GI motility or increased respiratory rate. Other emotions may result in loss of muscle tone and loss of control of bladder or of GI organs. These effects of emotions on the visceral organs are mediated through both sympathetic nerves and parasympathetic nerves of the autonomic nervous system. That is why some refer to the autonomic nervous system as the emotional-visceral nervous system.

Work Step by Step

Visceral organs (heart and blood vessels, GI organs, GU organs organs of the respiratory system) are innervated by both sympathetic and parasympathetic fibers of the autonomic nervous system. Sympathetic stimulation causes increase in heart rate , bronchiolar dilation but decrease gastric activity. These actions re opposed by parasympathetic action. In any case autonomic nervous system initiation , maintenance and modulation usually goes on without our conscious awareness of these activities. For instances changes in heart rate, blood pressure and body temperature takes place from hour to hour , but we are not consciously initiate these changes nor are usually aware of them. That is why this nervous system is called an involuntary nervous system. However, there can be CNS input into and adjustment of ANS control of these functions. When we experience emotions like anger, fear,shame, disappointment, love we sometimes say we feel them in our visceral organs( gut,heart).. This is not just a figure of speech. Emotions can cause increases or decreases in motor activities of visceral organs. Heart rate may increase, blood pressure may increase, GI motility may decrease, frequency of urination may increase.. These are all activities caused by emotions, but mediated through sympathetic and parasympathetic nerve fibers of the ANS. That is why it is appropriate to refer to the ANS as an emotional-visceral system
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