Question

Discuss the Physiology of the cardiac cycle

Answer 1

PHYSIOLOGY OF CARDIAC CYCLE
The heart is four chambered organ consisting of upper two chamber known as right and left atria where as lower two chamber known as right and left ventricles .

Atria are entry of blood flow returning from circulatory system . ventricles performs the contraction that eject the blood from the heart to flow through circulatory system.

Circulation is split into two :- Pulmonary circulation and Systemic circulation .

Pulmonary circulation id during which right ventricles pumps oxygenated depleted blood to the lungs through pulmonary arteries

Systemic circulation in which left ventricles pumps blood/ejects newly oxygenated blood throughout the body via aorta and all arteries .

Cardiac Cycle :- as the tricuspid and bicuspid valves are open then the blood from pulmonary veins and the vena cava flows into the left and right ventricle through left and right atria . During this stage semilunar valves are closed .

SA node generates the action potential which stimulates both atria undergo a contraction , this is known as atrial systole.

The action potential is conducted to ventricular side by AV node and AV bundle from where the bundle of HIS or perkinje fibers transmit it through the entire ventricular muscle which causes the ventricles to contract i.e ventricular systole, the atria undergoes relaxation i.e diastole which coincides with ventricular systole

Ventricular systole increases the ventricular pressure which closes the tricuspid and bicuspid valve , as the ventricular pressure increases further , the semilunar valve guarding the pulmonary artery and the aorta are forced open , which allows the blood in the ventricles to flow through these vessels in circulatory pathway .

when the ventricular pressure declines further , the tricuspid and bicuspid valves are pushed open by pressure in the atria exerted by the blood flow which was emptied into them by the veins and then blood moves freely to the ventricles which leads to ventricles and atria in a relaxed state i.e joint diastole .

then again SAN generates a new action potential and all these events are repeated as above mentioned .

During each cardiac cycle two sounds can be heard , the first is lub that is closure of tricuspid and bicuspid valve and where as second sound is dub that is closure of semilunar valves .

Cardiac output is the number of heart beats per minute .

The normal range of cardiac output is 4 to 8 L/min but depends upon body metabolic needs