|
The heart beat results in electropotential differences spreading over the heart muscles. These follow a specific pattern. Any change in the pattern indicates an abnormality. The pattern can be recorded using an electrocardiograph. The recorded pattern is called the electrocardiogram (ECG). This is an important diagnostic tool in detecting any defect in the structure and functioning of the heart.
The heart rate fast or slow, is controlled by the brain and is therefore called the nervous control The brain has two sites, cardiac accelerator site and the cardiac inhibitory site. The nerves run from these sites in the brain to the different nodes of the heart.
The number of times the heart beats per minute is called heart rate. For a normal adult human it is about 72 times per minute. For infants, it is a higher figure. It also goes up during physical exercise.
The contractions and relaxations that the heart chambers undergo are felt all along the arteries. If a finger is kept at a spot where an artery runs close to the surface, the rhythmic movement can be felt. This is called the pulse. It is found to be much the same as the heart rate. The number of pulses per minute is called the pulse rate.
There is also hormonal control over the heart rate. The common hormones known to increase the heart rate are the adrenaline and thyroxine. Adrenalin is secreted by the adrenal glands and thyroxine by the thyroid gland.
| 
