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 15.3 - Study Guide - Assess Your Learning Outcomes - Page 575: 7

Answer

The autonomic nervous system (ANS) often exerts control over certain organs and tissues through dual innervation, meaning that both the sympathetic and parasympathetic divisions of the ANS provide input to these organs. This dual innervation allows for precise and fine-tuned regulation of various physiological processes. Here are some examples of organs that receive dual innervation and how antagonistic and cooperative effects can occur: **1. Heart**: - **Antagonistic Effects**: - Sympathetic Division: When the sympathetic division is activated, it releases norepinephrine, which binds to beta-1 adrenergic receptors in the heart. This leads to an increase in heart rate (positive chronotropic effect) and contractility (positive inotropic effect), preparing the body for increased activity. - Parasympathetic Division: The parasympathetic division releases acetylcholine, which binds to muscarinic receptors in the heart. This leads to a decrease in heart rate (negative chronotropic effect) and a decrease in contractility (negative inotropic effect), promoting rest and digestion. - **Cooperative Effects**: - In certain situations, sympathetic and parasympathetic divisions can work cooperatively to fine-tune heart function. For example, during exercise, both divisions can be active to increase heart rate while maintaining cardiac output. **2. Digestive Tract**: - **Antagonistic Effects**: - Sympathetic Division: Sympathetic stimulation leads to reduced digestive motility and secretion by constricting blood vessels in the digestive organs. This is known as the "fight or flight" response. - Parasympathetic Division: Parasympathetic stimulation promotes increased digestive motility and secretion, facilitating the breakdown and absorption of nutrients during rest and digestion. - **Cooperative Effects**: - In some cases, both divisions can work together to optimize digestive processes. For example, the sympathetic division may reduce blood flow to the digestive organs to redirect it to the skeletal muscles during physical activity, while the parasympathetic division can enhance secretion and motility when needed for digestion. **3. Respiratory System**: - **Antagonistic Effects**: - Sympathetic Division: Sympathetic stimulation leads to bronchodilation (widening of the airways) by relaxing the smooth muscle in the bronchi and bronchioles, facilitating increased airflow. - Parasympathetic Division: Parasympathetic stimulation causes bronchoconstriction (narrowing of the airways) by contracting the smooth muscle in the bronchi and bronchioles, reducing airflow. - **Cooperative Effects**: - During exercise or situations requiring increased oxygen intake, both divisions can cooperate. The sympathetic division dilates the airways for increased airflow, while the parasympathetic division can modulate airway resistance to match the body's oxygen demand. In these examples, dual innervation of organs by the sympathetic and parasympathetic divisions allows for antagonistic effects, where one division promotes an action while the other inhibits it, and cooperative effects, where both divisions work together to achieve a balanced response. This precise regulation helps the body adapt to changing conditions and maintain homeostasis.

Work Step by Step

The autonomic nervous system (ANS) often exerts control over certain organs and tissues through dual innervation, meaning that both the sympathetic and parasympathetic divisions of the ANS provide input to these organs. This dual innervation allows for precise and fine-tuned regulation of various physiological processes. Here are some examples of organs that receive dual innervation and how antagonistic and cooperative effects can occur: **1. Heart**: - **Antagonistic Effects**: - Sympathetic Division: When the sympathetic division is activated, it releases norepinephrine, which binds to beta-1 adrenergic receptors in the heart. This leads to an increase in heart rate (positive chronotropic effect) and contractility (positive inotropic effect), preparing the body for increased activity. - Parasympathetic Division: The parasympathetic division releases acetylcholine, which binds to muscarinic receptors in the heart. This leads to a decrease in heart rate (negative chronotropic effect) and a decrease in contractility (negative inotropic effect), promoting rest and digestion. - **Cooperative Effects**: - In certain situations, sympathetic and parasympathetic divisions can work cooperatively to fine-tune heart function. For example, during exercise, both divisions can be active to increase heart rate while maintaining cardiac output. **2. Digestive Tract**: - **Antagonistic Effects**: - Sympathetic Division: Sympathetic stimulation leads to reduced digestive motility and secretion by constricting blood vessels in the digestive organs. This is known as the "fight or flight" response. - Parasympathetic Division: Parasympathetic stimulation promotes increased digestive motility and secretion, facilitating the breakdown and absorption of nutrients during rest and digestion. - **Cooperative Effects**: - In some cases, both divisions can work together to optimize digestive processes. For example, the sympathetic division may reduce blood flow to the digestive organs to redirect it to the skeletal muscles during physical activity, while the parasympathetic division can enhance secretion and motility when needed for digestion. **3. Respiratory System**: - **Antagonistic Effects**: - Sympathetic Division: Sympathetic stimulation leads to bronchodilation (widening of the airways) by relaxing the smooth muscle in the bronchi and bronchioles, facilitating increased airflow. - Parasympathetic Division: Parasympathetic stimulation causes bronchoconstriction (narrowing of the airways) by contracting the smooth muscle in the bronchi and bronchioles, reducing airflow. - **Cooperative Effects**: - During exercise or situations requiring increased oxygen intake, both divisions can cooperate. The sympathetic division dilates the airways for increased airflow, while the parasympathetic division can modulate airway resistance to match the body's oxygen demand. In these examples, dual innervation of organs by the sympathetic and parasympathetic divisions allows for antagonistic effects, where one division promotes an action while the other inhibits it, and cooperative effects, where both divisions work together to achieve a balanced response. This precise regulation helps the body adapt to changing conditions and maintain homeostasis.
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