-    CIRCULATORY - NERVOUS

-        - The heart rate is controlled by the nervous system. The sympathetic nerves are the ones that increase the heart rate while exercise and the parasympathetic nerves slow the heart rate when the body is calmed.

-       - The sympathetic nerves, carry nerve impulses from the brain to the heart. And the hear responds by increasing both the rate of contractions and the strength of the contraction.

-      -  The normal heart rate for an average adult is 60 to 100  beats per minute. This number can increase to a maximum heart rate during exercise that varies with age.