Contraction and Relaxation

Smooth muscle resembles the other muscle types in that contraction is triggered by calcium ions (Ca2+), energized by ATP, and achieved by the sliding of thin filaments over the

Smooth Muscle Contraction And Relaxation
Figure 11.23 Varicosities of an Autonomic Nerve Fiber in Single-Unit Smooth Muscle.

Saladin: Anatomy & I 11. Muscular Tissue I Text

Physiology: The Unity of Form and Function, Third Edition thick filaments. The mechanism of excitation-contraction coupling, however, is very different. Little of the Ca2+ comes from the sarcoplasmic reticulum; most comes from the extracellular fluid and enters the cell through calcium channels in the sarcolemma. Some of these channels are voltage-gated and open in response to changes in membrane voltage; some are ligand-gated and open in response to hormones and neurotransmitters; and some are mechanically gated and open in response to stretching of the cell.

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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