Heart beat

Mechanism?

The cardiac muscle is myogenic.

The heart beat starts at sinoatrial node/pacemaker.

The impulse from the pacemaker spread across both atria.

Both atria contract.

The impulse reach atrioventricular node.

Impulse travel through bundle of His to purkinje tissues/purkyne tissues.

And then spread to all parts of both ventricles.

Both ventricles contract/ventricular systole.

Control?

Cardiovascular centre is located in the medulla oblongata.

The heart is supplied by two nerves : vagus/parasympathetic and sympathetic nerves.

Impulse from cardiac inhibitory centre is transmitted to sinoatrial node through vagus nerve.

Vagus/parasympathetic nerve slows down the rate of heart beat.

Impulse from cardiac acceleratory transmitted to sinoatrial node through sympathetic nerves.

Sympathetic nerves increase/speed up the rate of heart beat.

Adrenaline/Epinepherine/Thyroxine also increases/speeds up the rate of heart beat.