What are the Different Phases of Cardiac Cycle?

Nov 14


Dr Carl Stephens

Dr Carl Stephens

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In order to know about the entire functioning of the heart sound, it is important to know about the phases of the cardiac cycle as well. Knowing about the whole process of the cardiac cycle will help you to figure out the scenario in which aorta, ventricle, atrium and cardiac valves are working.

Phases of the Cardiac Cycle – Systole & Diastole

Mechanical events are occurring during diastole and one systole.

One cardiac cycle = 1 systole + 1 diastole

In order to know the whole scenario of different Phases of the Cardiac Cycle,What are the Different Phases of Cardiac Cycle? Articles one should know about what happens within the atrium, cardiac valves, and ventricle in that phase. Events which are occurring in the left chambers of the heart are quite similar to the one which is occurring in the right chamber of the human heart.

Definition of Heart sounds (S1, S2, S3, S4)
  • S1 Heart Sound

Over the beginning of ventricle systole, tricuspid valves and mitral will produce a specific sound. This is basically the first heart sound.

  • S2 Heart Sound

Closure over the aortic along with the pulmonary valve which is at the end of the ventricle systole will produce a certain sound. This is the second heart sound.

  • S3 Heart Sound

As we are concerned about the rapid passive ventricular filling phase, the heart does often produce a specific sound. This is the third heart sound.

  • S4 Heart Sound

As we are concerned about the rapid passive ventricular filling phase, the heart does often produce a specific sound. This is the fourth heart sound.

For your convenience, you can also check out the graphical representation of the heart cycle to gain better access.

The first phase of the heart cycle will start from the atrial contraction in which the pressure of atrial will rise and let the bicuspid valve to get opened. Into the second phase, ventricles will begin to get into contracting. Just because the whole pressure of the ventricle has been high, mitral valves get closed too.

Rapid ventricular ejection is another most common phase of this whole cycle processing. As the pressure of ventricle gets higher as in comparison with the aortic pressure, the semilunar valve gets close to itself.

Quick Guide on Different Phases of Cardiac Cycle
  1. Atrial contraction

The first phase of the cycle is known as atrial contraction! 80% of the ventricular filling is completed through the onset of atrial contraction, whereas 20% of the ventricular filling is taking place because of atrial contraction. Ventricles active filling is extremely important during physical activity. 

  1. Isovolumetric Contraction

This is acknowledged to be the beginning section of the ventricular systole! Because the ventricles will contract, there'll be a sequence of modern amplification inside the intraventricular pressure. This is among the most important phases in any cardiac cycle.

This can also cause the bicuspid valve to face closure.  This closure of the bicuspid valve is going to be producing the very first sound of the guts. A contact set of bulging over the bicuspid valve proper interior the atrium will purpose a type of moderate make bigger inside the "c" wave and atrial pressure.

  1. Rapid Ventricular Ejection

As the strain will attain 81mmHg, the semilunar valve will begin to open up. This is regularly the cause when the 1/3 cycle of the cardiac has all started. Ventricles are going to be contracting, and there will be a crew of innovative increases inside the intraventricular stress of around 120mmHg.

  1. Slow Ventricular Ejection

Right into this phase, the atrium has been behaving due to the fact the reservoir of blood and consequently the timeline of the stress wave "v" is already building. The bicuspid valve is moreover closed.

Ventricles are nonetheless on its direction of contraction; however, due to the fact the blood intraventricular strain has been ejected, the stress will begin falling.  This is among the most important phases in any cardiac cycle. Plus the stress inside the aorta will begin to gall; however, the intraventricular stress is always higher as compared to the aortic pressure.

  1. Isovolumetric Relaxation

As the fifth segment comes in, the ventricles will begin to loosen up down! Intraventricles will get into the stress, which can begin to fall rapidly. Within the beginning stages, due to the fact the ventricular stress will subside than the stress inside the aorta, the aortic valves will close.

Even though at that point, the strain over the ventricles has been falling, it may be nonetheless excessive as in contrast to the stress interior of the atrium. During this phase, the atrium is behaving a bit like the reservoir of blood.

  1. Rapid Passive Ventricular Filling

When the left ventricles are inside the area of relaxation, the strain inside the left ventricles will begin to drop swiftly due to the fact it reaches over the reason when the stress of the ventricles is a smaller quantity as in contrast to the strain inside the atrium. This may additionally reason the opening of the bicuspid valve.

  1. Slow Passive Ventricular

Once the opening of the heart valve takes place, blood starts through the atrium and rushes directly into the ventricle. This is among the most important phases in any cardiac cycle. At this moment, the atrium is not actually working as being a reservoir.

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