Textbook Question
Which ANS fibers release acetylcholine? Which release norepinephrine?
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Ch. 14 The Autonomic Nervous System
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732
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Table of contents
- Ch. 1 The Human Body: An Orientation25
- Ch. 2 Chemistry Comes Alive24
- Ch. 3 Cells: The Living Units24
- Ch. 4 Tissue: The Living Fabric19
- Ch. 5 The Integumentary System12
- Ch. 6 Bones and Skeletal Tissues19
- Ch. 7 The Skeleton14
- Ch. 8 Joints7
- Ch. 9 Muscles and Muscle Tissue26
- Ch. 10 The Muscular System25
- Ch. 11 Fundamentals of the Nervous System and Nervous Tissue23
- Ch. 12 The Central Nervous System25
- Ch. 13 The Peripheral Nervous System and Reflex Activity30
- Ch. 14 The Autonomic Nervous System16
- Ch. 15 The Special Senses26
- Ch. 16 The Endocrine System26
- Ch. 17 Blood27
- Ch. 18 The Cardiovascular System: The Heart25
- Ch. 19 The Cardiovascular System: Blood Vessels27
- Ch. 20 The Lymphatic System and Lymphoid Organs and Tissues16
- Ch. 21 The Immune System: Innate and Adaptive Body Defenses27
- Ch. 22 The Respiratory System21
- Ch. 23 The Digestive System31
- Ch. 24 Nutrition, Metabolism, and Energy Balance26
- Ch. 25 The Urinary System26
- Ch. 26 Fluid, Electrolyte, and Acid-Base Balance24
- Ch. 27 The Reproductive System24
- Ch. 28 Pregnancy and Human Development25
- Ch. 29 Heredity11
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Not the one you use?Change textbook
Chapter 14, Problem 8
Describe the anatomical relationship of the white and gray rami communicantes to the spinal nerve, and indicate the kind of fibers found in each ramus type.
Verified step by step guidance1
Begin by identifying the spinal nerve as the main nerve trunk that emerges from the spinal cord and serves as a connection point for various nerve fibers.
Understand that the rami communicantes are two small nerve branches that connect the spinal nerve to the sympathetic trunk (a chain of ganglia involved in the autonomic nervous system). These are the white ramus communicans and the gray ramus communicans.
Describe the white ramus communicans as the branch that carries preganglionic sympathetic fibers from the spinal nerve to the sympathetic ganglia. Anatomically, it connects the spinal nerve to the sympathetic trunk and is typically found only at spinal levels T1 to L2.
Explain that the gray ramus communicans carries postganglionic sympathetic fibers from the sympathetic ganglia back to the spinal nerve. It connects the sympathetic trunk back to the spinal nerve and is present at all spinal levels.
Summarize the fiber types: the white ramus communicans contains myelinated preganglionic sympathetic fibers, while the gray ramus communicans contains unmyelinated postganglionic sympathetic fibers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
White and Gray Rami Communicantes
White and gray rami communicantes are nerve fibers connecting the spinal nerve to the sympathetic trunk. White rami carry preganglionic sympathetic fibers from the spinal nerve to the sympathetic ganglia, while gray rami carry postganglionic fibers back to the spinal nerve. Their color difference reflects the myelination status of the fibers.
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White & Gray Matter
Anatomical Relationship to the Spinal Nerve
Both rami communicantes connect to the spinal nerve near the intervertebral foramen. The white ramus enters the sympathetic trunk from the spinal nerve, typically found only in spinal segments T1 to L2, while the gray ramus exits the sympathetic trunk to rejoin the spinal nerve at all levels, allowing postganglionic fibers to reach peripheral targets.
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Types of Nerve Fibers in Each Ramus
White rami communicantes contain myelinated preganglionic sympathetic fibers, which transmit signals from the spinal cord to the sympathetic ganglia. Gray rami contain unmyelinated postganglionic sympathetic fibers that return from the ganglia to the spinal nerve, enabling sympathetic innervation of skin and blood vessels.
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Related Practice
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Where are the cell bodies of visceral sensory neurons?
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Briefly explain why the following terms are sometimes used to refer to the autonomic nervous system: involuntary nervous system and emotional-visceral system.
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