Anatomy & Physiology: The Unity of Form and Function, 7th Edition

Published by McGraw-Hill Education
ISBN 10: 0073403717
ISBN 13: 978-0-07340-371-7

Chapter 15 - Section 15.2 - Study Guide - Assess Your Learning Outcomes - Page 575: 5

Answer

Sympathetic preganglionic fibers, originating in the intermediolateral cell column of the spinal cord (T1 to L2 segments), have the potential to synapse with postganglionic neurons at various locations within the sympathetic nervous system. The specific location of synapse depends on the target organ or tissue and the pathway taken by the preganglionic fiber. Here are the various places where a sympathetic preganglionic fiber may synapse with a postganglionic neuron: 1. **Sympathetic Chain Ganglia**: - The most common location for synapse is within the sympathetic chain ganglia, which run parallel to the vertebral column. - Preganglionic fibers enter these ganglia through the white rami communicantes and synapse with postganglionic neurons within the same ganglion. - Postganglionic fibers then emerge from the ganglia to innervate various targets. 2. **Prevertebral Ganglia**: - Some preganglionic fibers pass through the sympathetic chain ganglia without synapsing and continue on to prevertebral ganglia located in the abdominal and pelvic cavities. - Examples of prevertebral ganglia include the celiac ganglion, superior mesenteric ganglion, and inferior mesenteric ganglion. - Preganglionic fibers synapse with postganglionic neurons in these prevertebral ganglia, which then send postganglionic fibers to innervate abdominal and pelvic organs. 3. **Adrenal Medulla**: - In some cases, preganglionic fibers bypass both the sympathetic chain and prevertebral ganglia and extend directly to the adrenal medulla, which is part of the adrenal glands located on top of the kidneys. - Instead of synapsing with postganglionic neurons, preganglionic fibers synapse with chromaffin cells in the adrenal medulla. - The chromaffin cells release epinephrine (adrenaline) and norepinephrine (noradrenaline) into the bloodstream, acting as hormones to affect various target tissues throughout the body. 4. **Gray Rami Communicantes**: - Some preganglionic fibers, after synapsing in sympathetic chain ganglia, may re-enter the spinal nerves through gray rami communicantes and then travel along the spinal nerves to reach specific targets. - This allows for sympathetic innervation of structures served by spinal nerves. The specific route taken by a sympathetic preganglionic fiber and the location of synapse depend on the target organ, the level of the spinal cord segment from which the fiber originates, and the functional requirements of the body's response to stress or stimuli. This flexibility allows the sympathetic nervous system to regulate a wide range of physiological functions and maintain homeostasis in response to changing conditions.

Work Step by Step

Sympathetic preganglionic fibers, originating in the intermediolateral cell column of the spinal cord (T1 to L2 segments), have the potential to synapse with postganglionic neurons at various locations within the sympathetic nervous system. The specific location of synapse depends on the target organ or tissue and the pathway taken by the preganglionic fiber. Here are the various places where a sympathetic preganglionic fiber may synapse with a postganglionic neuron: 1. **Sympathetic Chain Ganglia**: - The most common location for synapse is within the sympathetic chain ganglia, which run parallel to the vertebral column. - Preganglionic fibers enter these ganglia through the white rami communicantes and synapse with postganglionic neurons within the same ganglion. - Postganglionic fibers then emerge from the ganglia to innervate various targets. 2. **Prevertebral Ganglia**: - Some preganglionic fibers pass through the sympathetic chain ganglia without synapsing and continue on to prevertebral ganglia located in the abdominal and pelvic cavities. - Examples of prevertebral ganglia include the celiac ganglion, superior mesenteric ganglion, and inferior mesenteric ganglion. - Preganglionic fibers synapse with postganglionic neurons in these prevertebral ganglia, which then send postganglionic fibers to innervate abdominal and pelvic organs. 3. **Adrenal Medulla**: - In some cases, preganglionic fibers bypass both the sympathetic chain and prevertebral ganglia and extend directly to the adrenal medulla, which is part of the adrenal glands located on top of the kidneys. - Instead of synapsing with postganglionic neurons, preganglionic fibers synapse with chromaffin cells in the adrenal medulla. - The chromaffin cells release epinephrine (adrenaline) and norepinephrine (noradrenaline) into the bloodstream, acting as hormones to affect various target tissues throughout the body. 4. **Gray Rami Communicantes**: - Some preganglionic fibers, after synapsing in sympathetic chain ganglia, may re-enter the spinal nerves through gray rami communicantes and then travel along the spinal nerves to reach specific targets. - This allows for sympathetic innervation of structures served by spinal nerves. The specific route taken by a sympathetic preganglionic fiber and the location of synapse depend on the target organ, the level of the spinal cord segment from which the fiber originates, and the functional requirements of the body's response to stress or stimuli. This flexibility allows the sympathetic nervous system to regulate a wide range of physiological functions and maintain homeostasis in response to changing conditions.
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