Lengthtension relationship

The length of smooth muscle prior to stimulation has little influence on subsequent tension development. This is in marked contrast to skeletal muscle which exhibits a strong length-tension relationship. As discussed in Chapter 11, the influence of resting muscle length on the tension developed in skeletal muscle is based upon the arrangement of thick and thin filaments into sarcomeres. Any change in muscle length alters the degree of overlap of these filaments and therefore the number of crossbridges cycling and the amount of tension developed.

The contractile elements in smooth muscle are not organized into sar-comeres. Furthermore, the resting length of smooth muscle is much shorter than its optimal length. In other words, this muscle can be significantly stretched and the amount of tension developed may actually increase because the muscle is closer to its optimal length. Finally, thick filaments are longer in smooth muscle than they are in skeletal muscle. As a result, overlap of thick and thin filaments still occurs, even when the muscle has been stretched out.

This very broad length-tension relationship in smooth muscle is physiologically advantageous. Tubes and hollow organs may be stretched considerably as substances pass through them. Regardless, the smooth muscle must retain its ability to contract forcefully and regulate the movement of these substances through the organs.

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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