ATP

ATP powers all the activity of muscles. Muscles move because of the continual and instantaneous breakdown of ATP. The release of energy from ATP is a small thing, but essential to life itself. Muscle is an excitable tissue that it can be stimulated to produce an action potential. An action potential is an electrical change across the membrane. Muscle contraction requires a great deal of energy. The aerobic energy of a resting muscle comes two- …

…is to “absorb glucose molecules and used to rebuild their glycogen reserves” (Martini P. 301) in order to increase the output of the heart to meet the demands of energy and oxygen. The cardiac muscle is the greatest beneficiary. With this adaptation, the heart grows stronger. It draws more blood and oxygen through the coronary arteries and increases the amount of blood it pumps with each beat (stroke volume). This potentially adds years to its life-span.