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 15.1 - Study Guide - Assess Your Learning Outcomes - Page 575: 6

Answer

Autonomic efferent pathways and somatic efferent pathways are two distinct systems within the peripheral nervous system, and they differ in several key ways. One of the primary differences is the presence of ganglia and the number of motor neurons involved in transmitting signals from the central nervous system to the target organs. Understanding the concepts of preganglionic and postganglionic fibers is essential to grasp these differences. **Autonomic Efferent Pathways:** 1. **Two-Neuron Chain:** The autonomic efferent pathway consists of a two-neuron chain, which involves two motor neurons connected by a synapse in a ganglion. These motor neurons are called preganglionic and postganglionic neurons. 2. **Preganglionic Neuron:** The preganglionic neuron originates in the central nervous system (CNS) and extends to an autonomic ganglion outside the CNS. This neuron releases neurotransmitters that affect the postganglionic neuron in the ganglion. 3. **Postganglionic Neuron:** The postganglionic neuron extends from the autonomic ganglion to the target organ or tissue. It releases neurotransmitters that directly influence the effector (e.g., smooth muscle, cardiac muscle, glands) to which it is connected. 4. **Synaptic Transmission:** The synapse between the preganglionic and postganglionic neurons occurs in an autonomic ganglion, typically located outside the CNS. Neurotransmitters are used to transmit signals from the preganglionic to the postganglionic neuron. 5. **Involuntary Control:** Autonomic efferent pathways control involuntary processes, such as heart rate, digestion, and glandular secretion. They regulate internal organs and maintain homeostasis. **Somatic Efferent Pathways:** 1. **Single-Neuron Pathway:** The somatic efferent pathway consists of a single motor neuron that extends directly from the CNS to the skeletal muscles it innervates. There is no ganglion or synapse involved within the pathway. 2. **Control Over Skeletal Muscles:** Somatic motor neurons control voluntary muscle movement. They transmit signals from the CNS to the skeletal muscles, enabling conscious control of bodily movements. 3. **Neurotransmitter Release:** Somatic motor neurons release the neurotransmitter acetylcholine (ACh) at the neuromuscular junction, directly stimulating skeletal muscle contraction. 4. **Voluntary Control:** Somatic efferent pathways are under conscious, voluntary control. They allow individuals to decide when and how to move their skeletal muscles. **Preganglionic and Postganglionic Fibers:** - **Preganglionic Fibers:** These are the axons of the preganglionic neurons in both the sympathetic and parasympathetic divisions of the autonomic nervous system. Preganglionic fibers extend from the CNS to the autonomic ganglia, where they synapse with postganglionic neurons. They are typically myelinated and have a relatively short length. - **Postganglionic Fibers:** These are the axons of the postganglionic neurons in the autonomic ganglia. Postganglionic fibers extend from the ganglia to the target organs or tissues. They are usually unmyelinated and have a longer length than preganglionic fibers. In summary, autonomic efferent pathways involve a two-neuron chain with preganglionic and postganglionic neurons, and they control involuntary processes in internal organs. Somatic efferent pathways consist of a single motor neuron and control voluntary muscle movements in skeletal muscles. Understanding the distinctions between these systems and the roles of preganglionic and postganglionic fibers is important for comprehending how the autonomic and somatic nervous systems function in the body.

Work Step by Step

Autonomic efferent pathways and somatic efferent pathways are two distinct systems within the peripheral nervous system, and they differ in several key ways. One of the primary differences is the presence of ganglia and the number of motor neurons involved in transmitting signals from the central nervous system to the target organs. Understanding the concepts of preganglionic and postganglionic fibers is essential to grasp these differences. **Autonomic Efferent Pathways:** 1. **Two-Neuron Chain:** The autonomic efferent pathway consists of a two-neuron chain, which involves two motor neurons connected by a synapse in a ganglion. These motor neurons are called preganglionic and postganglionic neurons. 2. **Preganglionic Neuron:** The preganglionic neuron originates in the central nervous system (CNS) and extends to an autonomic ganglion outside the CNS. This neuron releases neurotransmitters that affect the postganglionic neuron in the ganglion. 3. **Postganglionic Neuron:** The postganglionic neuron extends from the autonomic ganglion to the target organ or tissue. It releases neurotransmitters that directly influence the effector (e.g., smooth muscle, cardiac muscle, glands) to which it is connected. 4. **Synaptic Transmission:** The synapse between the preganglionic and postganglionic neurons occurs in an autonomic ganglion, typically located outside the CNS. Neurotransmitters are used to transmit signals from the preganglionic to the postganglionic neuron. 5. **Involuntary Control:** Autonomic efferent pathways control involuntary processes, such as heart rate, digestion, and glandular secretion. They regulate internal organs and maintain homeostasis. **Somatic Efferent Pathways:** 1. **Single-Neuron Pathway:** The somatic efferent pathway consists of a single motor neuron that extends directly from the CNS to the skeletal muscles it innervates. There is no ganglion or synapse involved within the pathway. 2. **Control Over Skeletal Muscles:** Somatic motor neurons control voluntary muscle movement. They transmit signals from the CNS to the skeletal muscles, enabling conscious control of bodily movements. 3. **Neurotransmitter Release:** Somatic motor neurons release the neurotransmitter acetylcholine (ACh) at the neuromuscular junction, directly stimulating skeletal muscle contraction. 4. **Voluntary Control:** Somatic efferent pathways are under conscious, voluntary control. They allow individuals to decide when and how to move their skeletal muscles. **Preganglionic and Postganglionic Fibers:** - **Preganglionic Fibers:** These are the axons of the preganglionic neurons in both the sympathetic and parasympathetic divisions of the autonomic nervous system. Preganglionic fibers extend from the CNS to the autonomic ganglia, where they synapse with postganglionic neurons. They are typically myelinated and have a relatively short length. - **Postganglionic Fibers:** These are the axons of the postganglionic neurons in the autonomic ganglia. Postganglionic fibers extend from the ganglia to the target organs or tissues. They are usually unmyelinated and have a longer length than preganglionic fibers. In summary, autonomic efferent pathways involve a two-neuron chain with preganglionic and postganglionic neurons, and they control involuntary processes in internal organs. Somatic efferent pathways consist of a single motor neuron and control voluntary muscle movements in skeletal muscles. Understanding the distinctions between these systems and the roles of preganglionic and postganglionic fibers is important for comprehending how the autonomic and somatic nervous systems function in the body.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.