Plants and other things that make food for themselves and use the sun to make food
Your answer would be B
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Oxygen and carbon dioxide travels to and from tiny air sacs in the lungs, through the walls of the capillaries, into the blood. Blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs.
Smooth muscles depolarize as a result of a transmembrane current of Calcium ions. When an action potential depolarizes the muscle cell membrane, it also travels into the body of the cell via the t-tubules. Unlike skeletal muscle, smooth muscle is dependent in two sources of calcium in order to intiate contraction. These two sources are calcium sequestered in the S.R. of the smooth muscle cell.
