Human Heart Physiology and Cardiac Control

The contraction phase of the heart is called systole.

Diastole is the relaxation phase of the heart.

This phase is called ventricular diastole and is known as general phase.

At each heart beat ventricles pump about 70 ml of blood. This volume is called stroke volume.

Mammalian heart is myogenic heart, i.e heartbeat originates from muscle. The specialised area where impulses for contraction originate is called SA node.

Heartbeat originates from a muscular patch in the right auricle known as SA node. Thus, heartbeat originates from a muscle.

AV node picks up the wave of contraction propagated by SA node. The waves then pass through the Bundle of His, which passes down the intraventricular septum and divides into two branches, one of which is distributed to each ventricle through a fine network of Purkinje fibres. In this way, wave of contraction travels up to the ventricles.

The specialised tissue called SA is present close to the entrance of superior vena cava in the right auricle.

Bundle of His is the only direct muscular communication link between the auricle and ventricle.

Our heart pumps approx. 5040 ml of blood per minute. This is known as cardiac output.

Purkinje fibres run on the interior surface of the ventricles to join the working cardiomyocytes.

The bundle of His is an important part of the electrical conduction system of the heart as it transmits impulses from the atrioventricular node.

Both acetylcholine and pilocarpine lower the heart rate.

The cardiac centre lies in the medulla of the brain and is formed of cardioinhibitor and cardioacclerator.

The difference is that pulse is expansion and contraction of artery, whereas heart rate is contraction and relaxation of heart muscles.