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Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
ISBN: 9781337408332

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BuyFindarrow_forward

Biology: The Unity and Diversity o...

15th Edition
Cecie Starr + 3 others
ISBN: 9781337408332
Textbook Problem
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A motor unit is _________.

  1. a. a muscle and the bone it moves
  2. b. two muscles that work in opposition
  3. c. the amount a muscle shortens during contraction
  4. d. a motor neuron and the muscle fibers it controls

Summary Introduction

Introduction: A membrane-bound structure called sarcoplasmic reticulum is a specialized smooth endoplasmic reticulum that mainly functions in the regulation of calcium ions that are present in the striated muscle cells. The GABA (Gamma-Aminobutyric Acid) is a neurotransmitter that functions to inhibit the signals from the motor neurons.

Explanation

Reason for the correct answer:

A motor neuron possesses several axon endings that synapse on different muscle fibers. A motor neuron and all the muscle fibers will form a motor unit. If a motor neuron is activated, then the other muscle fibers will also start to contract simultaneously. The contracting muscles will utilize certain forces called as muscle tension, which depends upon several contracting muscle fibers.

Option d. is given as “a motor neuron and the muscle fibers it controls”.

A motor neuron and all the muscle fibers will form a motor unit.

Hence, the correct answer is option d.

Reasons for the incorrect answers:

Option a. is given as “a muscle and the bone it moves”.

This is incorrect because a motor neuron and all the muscle fibers will form a motor unit...

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