What is an advantage of a change in pulse rate after exercising?
(1) the heart needs to produce more energy to supply the active muscle cells and maintain homeostasis.
(2) an increased blood flow carries excess waste products away from the active muscle cells.
(3) the blood is removing oxygen from muscle cells that were not active and carrying it to muscle cells that
are active.
(4) the blood is supplying the active muscle cells with carbon dioxide to neutralize wastes in those cells.