The rapid depolarization phase
of myocardial contractile cells is due to the Na+ ions. Sodium ions are essential
for regulation of blood and body fluids, communication of nerve impulses, heart
activity, and metabolic purposes. Physiologically, it survives as an ion in the
body. Sodium is needed by
animals but is not needed by plants. The human prerequisite for sodium<span> must be less
than 500 mg per day. </span>
The Apollo program was designed to land humans on the Moon and bring them safely back to Earth.
The esophagus has a simple but significant functions to animals who has it. These functions can be a) to swallow food and serve as a passageway to the stomach and b) may serve to release the eaten food that might have some harmful compositions or chemicals -the vomit response.
The posterior opening is called the anus
