During exercise, metabolic activity in skeletal muscles incr…

During exercise, metabolic activity in skeletal muscles increases substantially. At the same time, sympathetic stimulation constricts blood vessels supplying some less-active organs. How do these responses help the cardiovascular system meet the body’s changing demands?

Blood returning from the body enters the heart and is then p…

Blood returning from the body enters the heart and is then pumped toward the lungs before eventually returning to the heart and being pumped to the body again. Which principle best explains how arteries and veins are classified within this continuous pathway?