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Ch. 16 The Autonomic Nervous System and Higher-Order Functions
Martini - Fundamentals of Anatomy and Physiology 12th Edition
Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011Not the one you use?Change textbook
Chapter 16, Problem 4

Effects produced by the parasympathetic branch of the ANS include
(a) Dilation of the pupils
(b) Increased secretion by digestive glands
(c) Dilation of respiratory passages
(d) Increased heart rate
(e) Increased breakdown of glycogen by the liver

Verified step by step guidance
1
Step 1: Understand the role of the parasympathetic branch of the autonomic nervous system (ANS). It is primarily responsible for 'rest and digest' activities, promoting maintenance functions and conserving energy.
Step 2: Analyze each option in the context of parasympathetic effects: (a) Dilation of the pupils is typically caused by the sympathetic nervous system, so this is unlikely a parasympathetic effect.
Step 3: Consider (b) Increased secretion by digestive glands. Since the parasympathetic system stimulates digestion, this effect aligns well with its function.
Step 4: Evaluate (c) Dilation of respiratory passages. This is generally a sympathetic response to increase airflow, so it is not a parasympathetic effect.
Step 5: Review (d) Increased heart rate and (e) Increased breakdown of glycogen by the liver. Both are sympathetic responses to prepare the body for 'fight or flight,' so they are not effects of the parasympathetic system.

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Key Concepts

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

Parasympathetic Nervous System Function

The parasympathetic branch of the autonomic nervous system (ANS) primarily promotes 'rest and digest' activities. It conserves energy by slowing the heart rate, stimulating digestive secretions, and promoting nutrient absorption. Understanding its role helps distinguish its effects from the sympathetic system.
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Physiological Effects of Parasympathetic Activation

Parasympathetic activation causes pupil constriction (not dilation), increased secretion by digestive glands, bronchoconstriction (narrowing of respiratory passages), and decreased heart rate. These effects support bodily functions during restful states, contrasting with the sympathetic 'fight or flight' responses.
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Comparison with Sympathetic Nervous System

The sympathetic nervous system triggers responses like pupil dilation, increased heart rate, bronchodilation, and glycogen breakdown for energy mobilization. Recognizing these opposing effects clarifies why certain options (e.g., pupil dilation, increased heart rate) are not caused by parasympathetic activity.
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