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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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_______ from a motor neuron excites a muscle fiber.

  1. a. ACh
  2. b. Calcium
  3. c. GABA
  4. d. Phosphate

Summary Introduction

Introduction: In the nervous control of contraction, the primary motor cortex is the portion where most of the voluntary movements take place. The brain receives the signals, and they travel to and stimulate a motor neuron. 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.

Explanation

Reason for the correct answer:

The brain receives the signals, and they travel to and stimulate a motor neuron. When an action potential reaches at the neuromuscular junction, it causes the release of the acetylcholine (ACh). Similar to neurons, a muscle fiber can also be stimulated, which means that they are able to experience an action potential. The ACh that is released at the neuromuscular junction has the ability to bind to the receptors in the muscle fiber’s plasma membrane. This binding activates an action potential that moves through the plasma membrane down to T tubules and then to the sarcoplasmic reticulum that wraps around the myofibrils and functions to store and release the calcium ions present in the striated muscle cells. It can permit to form cross-bridges between the actin and myosin during the contraction of muscles.

Option a. is given as “ACh”.

The brain receives the signals, and they travel to and stimulate a motor neuron. When an action potential reaches the neuromuscular junction, it causes the release of the acetylcholine (ACh)...

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