Ch. 13 The Peripheral Nervous System

Amerman - Human Anatomy & Physiology 2nd Edition

Amerman2nd EditionHuman Anatomy & PhysiologyISBN: 9780136873822Not the one you use?Change textbook

Amerman 2nd Edition

Ch. 13 The Peripheral Nervous System

Problem L2.3

Chapter 13, Problem L2.3

Explain why you lose both motor and sensory function of a part of your body when a spinal nerve is numbed with anesthetic agents.

Verified step by step guidance

Understand the structure of a spinal nerve: A spinal nerve is a mixed nerve that contains both motor and sensory fibers. Motor fibers carry signals from the central nervous system to muscles, while sensory fibers carry signals from sensory receptors to the central nervous system.

Recognize the role of anesthetic agents: Anesthetic agents block the transmission of nerve impulses by interfering with the function of ion channels in the nerve cell membranes. This prevents the nerve from sending signals effectively.

Identify the impact on motor function: When the motor fibers within the spinal nerve are numbed, the signals from the central nervous system to the muscles are interrupted. This results in a loss of motor function, meaning the affected muscles cannot contract or move properly.

Identify the impact on sensory function: When the sensory fibers within the spinal nerve are numbed, the signals from sensory receptors to the central nervous system are blocked. This results in a loss of sensory function, meaning the affected area cannot perceive sensations such as touch, pain, or temperature.

Conclude the combined effect: Since a spinal nerve contains both motor and sensory fibers, numbing it with anesthetic agents leads to a simultaneous loss of motor and sensory function in the area of the body served by that nerve.

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Key Concepts

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

Spinal Nerves

Spinal nerves are part of the peripheral nervous system and emerge from the spinal cord. Each spinal nerve is responsible for transmitting sensory information from the body to the brain and motor commands from the brain to the muscles. They are composed of both sensory (afferent) and motor (efferent) fibers, which means that any disruption in their function can affect both sensation and movement in the corresponding body area.

Anesthetic Agents

Anesthetic agents are substances used to induce a loss of sensation or consciousness during medical procedures. When applied to a spinal nerve, these agents block the transmission of nerve impulses by inhibiting the function of sodium channels in the nerve fibers. This blockage prevents both sensory signals from reaching the brain and motor signals from being sent to the muscles, resulting in a loss of both motor and sensory function in the affected area.

Nerve Blockade

Nerve blockade refers to the technique of interrupting the transmission of nerve impulses along a specific nerve or group of nerves. This is commonly achieved through the injection of anesthetic agents near the nerve. By blocking the nerve's ability to transmit signals, both sensory perception and motor control are temporarily lost in the area supplied by that nerve, which is why patients may experience numbness and paralysis in the targeted region.

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Related Practice

Textbook Question

Match each type of neuroglial cell with its correct function.

____ Schwann cells

____ Ependymal cells

____ Microglial cells

____ Oligodendrocytes

____ Satellite cells

____ Astrocytes

a. Phagocytic cells of the CNS

b. Surround the cell bodies of neurons in the PNS

c. Create the myelin sheath in the PNS

d. Anchor neurons and blood vessels, maintain extracellular environment around neurons, assist in repair of damaged brain tissue

e. Create the myelin sheath in the CNS

f. Ciliated cells in the CNS that produce and circulate the fluid around the brain and spinal cord

Predict what might happen if nociceptors were rapidly adapting instead of slowly adapting receptors. Would this change be beneficial or potentially harmful?

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Textbook Question

A spinal nerve divides into a(n)_____ that serves the anterior side of the body and the limbs and a(n)_____that serves the posterior side of the body.

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Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

e. There are 31 pairs of spinal nerves and 12 pairs of cranial nerves.

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Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

d. The term nerve is the equivalent of the term neuron.

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Textbook Question

Devise a series of physical examination tests that assess the function of each of the cranial nerves.

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