Textbook Question
Why is visceral pain often perceived as cutaneous pain?
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Ch. 13 The Peripheral Nervous System
Amerman2nd EditionHuman Anatomy & PhysiologyISBN: 9780136873822
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Table of contents
- Ch. 1 Introduction to Anatomy and Physiology26
- Ch. 2 The Chemistry of Life38
- Ch. 3 The Cell55
- Ch. 4 Histology47
- Ch. 5 The Integumentary System30
- Ch. 6 Bones and Bone Tissue36
- Ch. 7 The Skeletal System40
- Ch. 8 Articulations19
- Ch. 9 The Muscular System36
- Ch. 10 Muscle Tissue and Physiology29
- Ch. 11 Introduction to the Nervous System and Nervous Tissue28
- Ch. 12 The Central Nervous System42
- Ch. 13 The Peripheral Nervous System41
- Ch. 14 The Autonomous Nervous System and Homeostasis31
- Ch. 15 The Special Senses39
- Ch. 16 The Endocrine System42
- Ch. 17 The Cardiovascular System I: The Heart30
- Ch. 18 The Cardiovascular System II: The Blood Vessels43
- Ch. 19 Blood32
- Ch. 20 The Lymphatic System and Immunity45
- Ch. 21 The Respiratory System27
- Ch. 22 The Digestive System27
- Ch. 23 Nutrition and Metabolism7
- Ch. 24 The Urinary System39
- Ch. 25 Fluids, Electrolytes, and Acid-Base Homeostasis39
- Ch. 26 The Reproductive System10
- Ch. 27 Development and Heredity5
Chapter 13, Problem 12
How do upper and lower motor neurons differ?
Verified step by step guidance1
Understand that motor neurons are responsible for transmitting signals from the central nervous system (CNS) to muscles to produce movement. They are categorized into upper motor neurons (UMNs) and lower motor neurons (LMNs) based on their location and function.
Upper motor neurons (UMNs) originate in the motor cortex of the brain or the brainstem. They are responsible for initiating and modulating voluntary movements by sending signals to lower motor neurons. UMNs do not directly innervate muscles.
Lower motor neurons (LMNs) are located in the anterior horn of the spinal cord or in cranial nerve nuclei in the brainstem. They directly innervate skeletal muscles and are responsible for executing the movement commands received from UMNs.
Recognize the key difference: UMNs are part of the central nervous system and act as intermediaries, while LMNs are part of the peripheral nervous system and directly stimulate muscle contraction.
Consider clinical implications: Damage to UMNs often results in spastic paralysis, hyperreflexia, and increased muscle tone, while damage to LMNs leads to flaccid paralysis, muscle atrophy, and hyporeflexia.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Upper Motor Neurons
Upper motor neurons (UMNs) originate in the brain and project down to the spinal cord, where they synapse with lower motor neurons. They are responsible for conveying signals that initiate and control voluntary movements. Damage to UMNs can lead to symptoms such as spasticity and hyperreflexia, indicating a disruption in the normal control of muscle activity.
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04:20
The Neuron
Lower Motor Neurons
Lower motor neurons (LMNs) are located in the spinal cord and brainstem, directly innervating skeletal muscles. They receive input from upper motor neurons and are crucial for executing voluntary movements. Damage to LMNs can result in muscle weakness, atrophy, and fasciculations, reflecting a loss of direct muscle stimulation.
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04:20The Neuron
Neurological Pathways
Neurological pathways refer to the connections between neurons that facilitate communication within the nervous system. The pathway from upper to lower motor neurons is essential for coordinated movement. Understanding these pathways helps in diagnosing and treating motor disorders, as disruptions can lead to various clinical symptoms.
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4:40Alternative Pathway
Related Practice
Textbook Question
Place the following sequence of events for the detection of somatic sensation in the proper order. Place a 1 by the first event, a 2 by the second event, and so on.
a. ______The central process transmits the action potential to a second-order sensory neuron in the CNS.
b. ______The action potential is transferred to the central process in the posterior root ganglion.
c. ______The stimulus triggers an action potential.
d. ______The signal is transferred to other CNS sensory neurons for eventual perception and interpretation.
e. ______The action potential is propagated along the peripheral process of the neuron.
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Textbook Question
Mark the following statements about the spinal cord as true or false. If a statement is false, correct it to make a true statement.
The corticospinal tracts are the main sensory tracts in the spinal cord.
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Textbook Question
The tracts of the posterior columns decussate in the ________, whereas the tracts of the anterolateral system decussate in the ________.
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Textbook Question
List and describe the basic steps involved in producing movement, beginning with the upper motor neurons in the cerebral cortex.
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Textbook Question
Which parts of the body have the greatest amount of space dedicated to them in the primary somatosensory cortex? Why?
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