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Ch. 14 The Autonomic Nervous System
Hoehn - Marieb Human Anatomy & Physiology, 12th edition
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Not the one you use?Change textbook
All textbooksHoehn, Haynes, Abbott 12th EditionCh. 14 The Autonomic Nervous SystemProblem 5
Chapter 14, Problem 5

Which ANS fibers release acetylcholine? Which release norepinephrine?

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Understand that the autonomic nervous system (ANS) is divided into two main branches: the sympathetic and parasympathetic nervous systems, each with distinct neurotransmitters.
Identify that parasympathetic fibers release acetylcholine (ACh) at both their preganglionic and postganglionic synapses, meaning both sets of fibers in this division are cholinergic.
Recognize that sympathetic fibers release acetylcholine at their preganglionic synapses, but most postganglionic sympathetic fibers release norepinephrine (NE), making them adrenergic.
Note the exception that some sympathetic postganglionic fibers, such as those innervating sweat glands, also release acetylcholine instead of norepinephrine.
Summarize: Parasympathetic pre- and postganglionic fibers release acetylcholine; sympathetic preganglionic fibers release acetylcholine; sympathetic postganglionic fibers mostly release norepinephrine, with some exceptions releasing acetylcholine.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Autonomic Nervous System (ANS) Divisions

The ANS is divided into the sympathetic and parasympathetic systems, each controlling involuntary body functions. Understanding these divisions is essential because they differ in the types of neurotransmitters their fibers release and their physiological effects.
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Divisions of the ANS

Cholinergic Fibers and Acetylcholine

Cholinergic fibers are nerve fibers that release acetylcholine as their neurotransmitter. In the ANS, all preganglionic fibers (both sympathetic and parasympathetic) and parasympathetic postganglionic fibers release acetylcholine to transmit signals to target organs.
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Adrenergic Fibers and Norepinephrine

Adrenergic fibers release norepinephrine as their neurotransmitter. In the ANS, most sympathetic postganglionic fibers are adrenergic, meaning they release norepinephrine to activate target tissues, contributing to the 'fight or flight' response.
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Related Practice
Textbook Question

Collateral sympathetic ganglia are involved with innervating

a. abdominal organs

b. thoracic organs

c. head

d. arrector pili

e. all of these

Textbook Question

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.

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Textbook Question

The white rami communicantes contain what kind of fibers?

a. Preganglionic parasympathetic

b. Postganglionic parasympathetic

c. Preganglionic sympathetic

d. Postganglionic sympathetic

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Textbook Question

Where are the cell bodies of visceral sensory neurons?

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Textbook Question

Briefly explain why the following terms are sometimes used to refer to the autonomic nervous system: involuntary nervous system and emotional-visceral system.

Textbook Question

Relate each of the following terms or phrases to either the sympathetic (S) or parasympathetic (P) division of the autonomic nervous system: 

______ (1) Short preganglionic, long postganglionic fibers 

______ (2) Intramural ganglia 

______ (3) Craniosacral part 

______ (4) Adrenergic fibers 

______ (5) Cervical ganglia 

______ (6) Otic and ciliary ganglia

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