The rate of the triggering S-A impulses is regulated by the autonomic nervous system, which operates without conscious control. In this way the heartbeat accelerates or slows in response to physical activity and other factors. The action of the heart can be heard through a listening device, called a stethoscope, placed against the chest. Murmurs may indicate that blood is leaking through an imperfectly closed valve and may signal the presence of a serious heart problem. Cardiovascular Disease Cardiovascular disease disease of the heart or blood vessels can develop in any part of the circulatory system.
Problems can occur with the valves, the sinoatrial node, the heart muscle, or the blood vessels.
Arteriosclerosis, commonly called hardening of the arteries, includes a variety of conditions in which artery walls thicken and lose elasticity. There is evidence that heredity and a high cholesterol level in the blood can lead to atherosclerosis, the most common form of arteriosclerosis Hypertension. The force of the blood being pumped through the arteries exerts pressure on the arterial walls. When this pressure is too high it is an unhealthy condition called hypertension, or, simply, high blood pressure. If left untreated, it can lead to heart attack, stroke, kidney disease, or other illnesses.