Cardiac cycle

One Cardiac cycle= 1 systole and 1 diastole

      The normal systole pressure is 120mmhg

       The normal diastole pressure is 80mmhg

Systolic pressure

•    When the left ventricle contracts. the pressure ejected, into aorta from the ventricle. This pressure Is called systolic pressure. 120mmhg is the systolic pressure.

Diastolic pressure

• After ventricle relaxation. the aortic valve gets closes, inorder to stop back flow of the blood. The pressure which remained in the aorta is called diastolic pressure. The diastolic pressure is 80mmhg.

 The total cardiac cycle or heart beat, takes about 0.8 seconds.

     Stroke volume: 

 The amount of blood pumps into the aorta, by the left ventricle in one contraction is called stroke volume.

 The cardiac cycle under goes 7 phases.

 1. Atrial contraction

• When the atrium starts contraction, the mitral valve opens into ventricle. While the atrium contracting, The pressure in left atrium makes a small wave, this wave is called 'A' wave. This wave indicates 'P' wave in ecg. While atrium contracting, the blood falls from atrium to ventricle. In the end of this phase atrium and ventricle act as a same chambers, the pressure in both chamber are same.

2. Iso volumetric contraction  

•  This phase is defined as time between the closing of mitral valve and opening of aortic valve. Before the ventricle contracts, The pressure in ventricle is 0. After the blood falls in ventricle from atrium, The pressure raised 0 to 5mmhg, but due to increased of pressure in ventricle, more then the atrium. The mitral valve closes.
• During ventricle contraction the pressure in left ventricle gives a upward jerk to mitral valve, that makes formation of ' C' wave in atrium.

3. Rapid ventricular ejection phase

•  When the ventricle contracts more. The pressure reaches to 120mmhg, then the aorta valve opend. Here the aortic chamber and left ventricle act as a same chamber. The pressure in these two chamber are same 120mmhg

4. Slow ventricular filling phase

• In this phase the ventricles are still contacting, the intra ventricular pressure and aortic pressure starts falling. But still the pressure in ventricle is more then the aortic pressure, so  the aorta valves are opened.

5. Iso volumetric relaxing phase 

• In this phase both the aortic and mitral valves closed. The heart relaxes iso volumetric, both the outflow and inflow valves were closed, So no fluid cross over them. Thus the ventricle goes under diastole.

6.Rapid passive ventricular filling phase

• After the ventricle pumps the blood into aorta, some amount of blood remained in ventricle, this blood volume is called end systolic volume. After the ventricle complete relaxes, The pressure in ventricle no more. Then mitral valve opening takes place. Then the rapid fall of blood takes place in ventricle from atrium.

7. Slow passive ventricular filling phase

• In this phase, the mitral valve opens.
•  The atrium acts as a pipe to flow the blood into ventricle.
• In this way cardiac cycle completes.

 Cardiac cycle explained in wiggers diagram

 * Atrial contraction

 pressure in atrium creates 'A' wave in the atrium. 

 * Iso volumetric contraction

 the ventricle raises it's pressure upto 80mmhg, But here the ventricle pressure is lower then aortic pressure. So the aorta valve not opened. And due to the jerk of ventricle pressure, 'c' wave formed in atrium. 

* Rapid ventricular ejection phase

in this phase  the ventricles raises it's pressure from 80 to 120mmhg. Then the aortic valve opens and the blood flows to aorta.

* Slow ventricular filling phase

The ventricle starts falling it's it's pressure slowly from 120 mmHg to 80mmHg.

* Iso volumetric relaxing phase.

The complete falling of pressure in the ventricle takes place. In this phase the ventricle pressure is falls to 0mmhg.

* Rapid ventricular filling phase

In this the phase the ventricle pressure is lower then the atrium and aorta .

Heart sounds

• Heart sounds are 4types
• There are S1 and S2 and S3 and S4

* S1. Beginning of ventricle systol, the intra ventricular pressure goes up and the closure of both mitral valve and tricuspid valve. At onset of the ventricle systol the first heart sound is recorded as S1. 

* S2. during the ventricle diastole the pressure in the ventricles is falls down than the aorta. So the aortic valve and pulmonary valve closes. By this second heart is recorded as S2.

* S3. In younger people after exercise, The atrium pumps more blood to the ventricle. That produces the sound S3.

 * S4. It is an abnormality of heart sound. The patient with hypertrophy. The atrium pumps blood to the stiffened ventricle with very hard pressure. It may produce the sound S4.