Extrinsic Regulation of Heart in animals
Heart regulates its cardiac output based on the functional blood requirement of different parts of the body by adjusting its rate. Heart rate is directly proportional to metabolic activity, but inversely proportional to the size of the animal. Large animals have a slower heart rate than smaller ones. Athletic animals (Hare) and animals trained for exercise (Greyhound) has slower heart rate than rabbit or untrained animals of the same species.
Heart rate is also slow in male and adult animals than in female and young ones. Extrinsic regulation of heart may be achieved by two means- Nervous regulation and and Chemical regulation.