Muscular pump sending blood to all parts of the body through a highly intricate network of blood vessels called capillaries.
Weight: less than 0.45 kg (one pound)
Length: 13 cm (5 inches)
Width: 9 cm (3 1/2 inches)
The heart beats on average 70 times a minute and 100,000 times a day without rest. Your heart is actually two pumps joined together. Each one has an upper chamber, or atrium, into which blood enters. Blood then passes on to a lower, thick-walled chamber, or ventricle, which pumps blood out of the heart. The pump on the right side pushes blood to your lungs. It then returns to the pump on the left, which pushes it around your body.
Your heart pumps blood around your body supplying it with oxygen for energy. The rate at which your hert beats is adjusted automatically by the autonomic nervous system. During exercise, your demand for energy increases and the sympathetic nervous system causes your heart to beat faster. When you stop exercising, the demand for energy is reduced and the parasympathetic system slows your heart down. At rest, the two systems work together to maintain a steady heart rate.
EXERCISING – THE HEART
Your heart can pump up to five times more blood to the body every minute when you exercise. The amount of blood leaving the heart each time it pumps increases by 10 to 35 percent. Also, the number of times the heart beats per minute (the heart rate) can more than double its normal count.