In: Anatomy and Physiology
1) Distinguish between blood flow rate and blood flow velocity. When an expert in the field uses the term blood flow, does that term usually mean rate or velocity?
2) Explain why a heart can keep beating after it has been removed from a living body.
Ans 1) Blood flow rate is the rate of movement of the blood through a vessel, organ or tissue within a given time interval and the rate at which the blood flows depend on many factors. It depends on the blood pressure as well as the resistance in the blood flow that can be caused by the blood vessels. Generally, the blood flow rate is the total volume of blood that flows per unit of time. The cardiac output is one of the major factors which influences the blood flow rate.
The blood flow velocity is the measurement of rate of movement of the blood through a vessel and rate of the blood flow is one of the important factors. So basically the blood flow velocity is the rate of blood which is transported per unit time within a vessel. The difference between blood flow rate and blood flow velocity is that when the blood flow is constant, the velocity of blood flow is inversely proportional to the blood vessel cross sectional area.
When the expert uses the term blood flow, it basically means the rate of the blood flow through a vessel. Hence it is basically the rate at which the blood is able to enter a given vessel and into an organ and tissue.
Ans 2) The heart continues to beat even after it is removed from a living person as the nerve cells that are present in the heart continue to fire the electrical or nerve impulse for a longer period. The heart continues to beat till there is ATP present which powers the nerve cells to continue firing the impulse. In presence of oxygen and till ATP source is not exhausted the nerve cells fire impulse and hence the heart can continue beating. Gradually when the blood supply completely stops and ATP is depleted, it will stop beating. The pacemaker cells in the heart are able to generated their own electrical impulse and hence it continues to beat.