Myosin can only bind to actin when the binding sites on actin are exposed by calcium ions. Actin molecules are bound to the Z line, which forms the borders of the sarcomere. Other bands appear when the sarcomere is relaxed. A muscle fiber from a biceps muscle may contain 100,000 sarcomeres.uscle fibers are composed of tubular myofibrils. Myofibrils are composed of repeating sections of sarcomeres, which appear under the microscope as dark and light bands. Sarcomeres are composed of long, fibrous proteins as filaments that slide past each other when a muscle contracts or relaxes.
Even people with binge-eating disorder who are overweight are acutely aware of their body shape and appearance, and berate themselves after eating binges. The constant reinforcement of thinness may worsen her self-image and actually lead to more frequent bingeing as a woman seeks relief from feelings of shame.
Medications may be used to help with some of the associated symptoms. At five years about 70% of people with anorexia and 50% of people with bulimia recover. Recovery from binge eating disorder is less clear and estimated at 20% to 60%. Both anorexia and bulimia increase the risk of death. In the developed world binge eating disorder affects about 1.6% of women and 0.8% of men in a given year. Anorexia affects about 0.4% and bulimia affects about 1.3% of young women in a given year. During the entire life up to 4% of women have anorexia, 2% have bulimia, and 2% have binge eating disorder. Anorexia and bulimia occur nearly ten times more often in females than males.