Muscle Action

Muscles work in pairs to produce movement at the joints (see Display 20-1 for a description of various types of movement). As one muscle, the prime mover, contracts, an opposing muscle, the antagonist, must relax. For example, when the biceps brachii on the anterior surface of the upper arm contracts to flex the arm, the triceps brachii on the posterior surface must relax (Fig. 20-2). When the arm is extended, these actions are reversed. In a given movement, the point where the muscle is attached to a stable part of the skeleton is the origin; the point where a muscle is attached to a moving part of the skeleton is the insertion.

Was this article helpful?

0 0
From PMS To PPD

From PMS To PPD

The Stages Of A Woman’s Life Are No Longer A Mystery. Get Instant Access To Valuable Information On All The Phases Of The Female Body From Menstruation To Menopause And Everything In Between.

Get My Free Ebook


Post a comment