Regulation of cardiac activity and disorders

The heart's normal activity is regulated from within by nodal tissue, so the heart is called myogenic.

A special neural centre in the medulla oblongata can moderate heart function through the autonomic nervous system (ANS).

Sympathetic nerve signals increase the heart rate, the strength of ventricular contraction and so the cardiac output. Parasympathetic signals decrease the heart rate, the speed of conduction of the action potential and so the cardiac output. Adrenal medullary hormones can also raise the cardiac output.

Hypertension is blood pressure above normal, 120/80: 120 mm Hg is the systolic (pumping) pressure and 80 mm Hg the diastolic (resting) pressure. Repeated readings of 140/90 or higher indicate hypertension, which leads to heart disease and harms vital organs such as brain and kidney.

Coronary artery disease (CAD), often called atherosclerosis, affects the vessels supplying the heart muscle; deposits of calcium, fat, cholesterol and fibrous tissue narrow the lumen of the arteries.

Angina (angina pectoris) is acute chest pain when not enough oxygen reaches the heart muscle. It can occur at any age in men and women but is commoner in the middle-aged and elderly, and results from conditions that affect blood flow.

Heart failure is when the heart does not pump blood effectively enough to meet the body's needs. Because fluid backs up and congests the lungs, a key sign, it is also known as congestive heart failure.

Heart failure is not cardiac arrest, in which the heart stops beating, nor a heart attack, in which a sudden shortfall of blood supply injures part of the heart muscle.