How does elevation help in controlling bleeding?

Elevation helps control bleeding primarily by slowing it down through the process of raising the affected extremity above the level of the heart. When an injured limb is elevated, gravity assists in reducing the blood flow to the area, aiding in the constriction of blood vessels. This elevation can mitigate blood loss by reducing hydrostatic pressure in the vessels of the injured area, allowing blood coagulants to work more effectively.

The other options do not accurately capture the mechanism by which elevation affects bleeding. Stopping all blood flow is not feasible with elevation alone; it may reduce flow but does not completely halt it. Increasing blood pressure is not a direct effect of elevation and can actually lead to increased bleeding in some scenarios if the injury involves significant trauma. Finally, elevation does not directly reduce heart rate; heart rate may vary based on a multitude of factors including the body's response to injury, but elevation itself primarily impacts bleeding through changes in blood flow.