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Ch. 11 Introduction to the Nervous System and Nervous Tissue
Amerman - Human Anatomy & Physiology 2nd Edition
Amerman2nd EditionHuman Anatomy & PhysiologyISBN: 9780136873822Not the one you use?Change textbook
All textbooksAmerman 2nd EditionCh. 11 Introduction to the Nervous System and Nervous TissueProblem L2.1
Chapter 11, Problem L2.1

Would you expect to find larger motor units in the postural muscles of the back or the muscles of the hand? Explain your answer.

Verified step by step guidance
1
Understand the concept of motor units: A motor unit consists of a single motor neuron and all the muscle fibers it innervates. The size of a motor unit is determined by the number of muscle fibers controlled by a single motor neuron.
Recognize the functional difference between postural muscles and hand muscles: Postural muscles, such as those in the back, are responsible for maintaining posture and stability over long periods, while hand muscles are involved in fine motor control and precise movements.
Relate motor unit size to function: Larger motor units are typically found in muscles that perform gross, sustained movements (e.g., postural muscles), as they do not require fine control. Smaller motor units are found in muscles requiring precise, delicate movements (e.g., hand muscles).
Apply this understanding to the question: Since postural muscles of the back are involved in maintaining stability and do not require fine control, they are expected to have larger motor units. In contrast, the muscles of the hand, which perform intricate tasks, require smaller motor units for precise control.
Conclude the reasoning: Based on the functional demands of these muscle groups, you would expect to find larger motor units in the postural muscles of the back compared to the muscles of the hand.

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Key Concepts

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

Motor Units

A motor unit consists of a single motor neuron and all the muscle fibers it innervates. The size of a motor unit can vary, with larger units typically controlling more muscle fibers, which allows for greater force production. Smaller motor units, on the other hand, are found in muscles requiring fine motor control, such as those in the hand.
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Postural Muscles vs. Fine Motor Muscles

Postural muscles, like those in the back, are designed for stability and endurance, often requiring larger motor units to generate sustained force. In contrast, the muscles of the hand are involved in intricate movements and require smaller motor units for precise control, allowing for delicate tasks such as writing or playing an instrument.
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Force Production and Control

The relationship between motor unit size and force production is crucial in understanding muscle function. Larger motor units can produce more force but lack the precision needed for fine movements. Therefore, in the context of the question, one would expect to find larger motor units in postural muscles due to their role in maintaining stability and supporting the body.
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Related Practice
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Explain how an action potential is propagated down an axon in continuous conduction. Why is saltatory conduction faster than continuous conduction?

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What would happen if the drug blocked K+ channels instead?

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