Smooth Muscles page 315

The contractile mechanisms of smooth and cardiac muscles are similar to those of skeletal muscle.

1. Smooth muscle fibers a. Smooth muscle cells contain filaments of myosin and actin.

b. They lack transverse tubules, and the sarcoplasmic reticula are not well developed.

c. Types include multiunit smooth muscle and visceral smooth muscle.

d. Visceral smooth muscle displays rhythmicity.

e. Peristalsis aids movement of material through hollow organs.

2. Smooth muscle contraction a. In smooth muscles, calmodulin binds to calcium ions and activates the contraction mechanism.

b. Both acetylcholine and norepinephrine are neurotransmitters for smooth muscles.

c. Hormones and stretching affect smooth muscle contractions.

d. With a given amount of energy, smooth muscle can maintain a contraction for a longer time than can skeletal muscle.

e. Smooth muscles can change length without changing tautness.

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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