Textbook Question
Mark the following statements as true or false. If a statement is false, correct it to make a true statement.
d. Sympathetic tone controls the resting rate of the heart.
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14. The Autonomic Nervous System
Sympathetic Nervous System
Problem 14
Textbook Question
How does the emergence of sympathetic fibers from the spinal cord differ from the emergence of parasympathetic fibers?
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Understand the basic organization of the autonomic nervous system (ANS), which is divided into the sympathetic and parasympathetic divisions. The sympathetic division is responsible for 'fight or flight' responses, while the parasympathetic division handles 'rest and digest' functions.
Learn the anatomical origin of sympathetic fibers. Sympathetic fibers emerge from the thoracolumbar region of the spinal cord, specifically from the lateral horns of spinal segments T1 to L2. These fibers are part of the sympathetic chain ganglia.
Contrast this with the anatomical origin of parasympathetic fibers. Parasympathetic fibers emerge from the craniosacral region, which includes cranial nerves III, VII, IX, and X, as well as sacral spinal segments S2 to S4.
Examine the pathway of sympathetic fibers. After emerging from the spinal cord, sympathetic fibers travel through the ventral root, join the spinal nerve, and then enter the sympathetic chain ganglia via the white rami communicantes. From there, they may synapse or travel to target organs.
Compare this to the pathway of parasympathetic fibers. Parasympathetic fibers typically synapse in ganglia located near or within the target organs, such as the ciliary ganglion for cranial nerve III or the intramural ganglia for sacral fibers. This is a key difference in the organization and function of the two divisions.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Sympathetic Nervous System
The sympathetic nervous system is part of the autonomic nervous system responsible for the body's 'fight or flight' response. Sympathetic fibers emerge from the thoracic and lumbar regions of the spinal cord, specifically from T1 to L2. These fibers typically synapse in ganglia located close to the spinal cord, allowing for a rapid response to stressors.
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Parasympathetic Nervous System
The parasympathetic nervous system is another component of the autonomic nervous system, primarily responsible for 'rest and digest' functions. Parasympathetic fibers emerge from the brainstem and the sacral region of the spinal cord (S2 to S4). These fibers usually synapse in ganglia located near or within the target organs, promoting a more localized and slower response.
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Autonomic Nervous System
The autonomic nervous system (ANS) regulates involuntary physiological functions, including heart rate, digestion, and respiratory rate. It is divided into the sympathetic and parasympathetic systems, which have opposing effects on the body. Understanding the ANS is crucial for comprehending how sympathetic and parasympathetic fibers differ in their origin, pathways, and functions.
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