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NEET UG 2026 » NEET UG Study Material » Biology » Joint Diastole
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Joint Diastole

Joint diastole occurs when the heart's four chambers are all relaxed. This article will be your ultimate guide to joint diastole.

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The heart’s principal role is to pump blood throughout the body in a repeating rhythm. Electrical impulses govern the filling and emptying of the heart’s blood by contracting and relaxing the muscles. 

The heart beats 100,000 times a day on average. The heart’s pumping phase, known as the systole, is followed by a resting phase, known as the diastole, during which the heart rests. The atria constrict forces blood through the atrioventricular valves into the ventricles. A trill-like “lub” sound is created when the atrioventricular valves are shut off completely. There is a “dub” sound created while closing the semilunar valves. 

Now, let’s go into the nitty-gritty of joint diastole and its many roles.

What is Joint Diastole?

  • The cardiac cycle is the time the heart takes to get from one beat to the next. There are two distinct phases: diastole, during which the heart muscle relaxes and replenishes its blood supply, and systole when the heart muscle contracts and pumps blood forcefully.

  • When all the chambers are relaxed, it is referred to as “joint diastole.” Blood goes to the auricles of each joint at this time through a vein.

  • Bicuspid and Tricuspid valves open when the joint is dilated, enabling blood to pass from the atrium to the ventricles, although semilunar valves stay closed.

  • Diastole occurs simultaneously in the ventricles and the auricles. The pressure in the heart’s aorta falls in the major arteries as diastole progresses. Semilunar valves close quickly to prevent the backflow of blood from large arteries into the ventricles. The “dup” sound is produced by the fast closure of the semilunar valves in the ventricular diastole.

The sounds the heart produces can be used to assess the health of the heart valves. Blood can overflow from the ventricles to the auricles or from the aorta to the ventricles because of damaged or malfunctioning cardiac valves. It is possible to discover these defects by listening for a distinct “murmur”. A damaged valve can be removed surgically or repaired. Rheumatic fever and syphilis both cause wheezing as a symptom. 

An amplifier and recorder of heartbeat sounds are known as the Phonocardiogram.

Joint Diastole: Meaning and Function

Diastole, or the beginning of relaxation and dilation, occurs as the heart’s four chambers — two atria and two ventricles — approach in unison. The atria fill up with different blood volumes returning from the vena cavae to the right atrium and the left atrium, respectively (from the lungs). The mitral and tricuspid valves open when chamber and back pressures are equal, and returning blood flows through the atria and into the ventricles. To force blood into the ventricles, the atria begin to contract, which results in the ventricles filling to capacity. The mitral and tricuspid valves now close when the pressure in the ventricles increases.

To put it another way, as blood pressures in the ventricles continue to rise, so does “back pressure” in the arteries. The heart’s aortic and pulmonary valves open, allowing blood to flow out of it. Ventricle pressure decreases due to ejection, which also causes a rise in heart rate when the atria refill (atrial diastole). Ventricle pressures fall below the back pressures in the aortic and respiratory arteries’ trunks, and the valves on both vessels close. As the ventricles relax, the mitral and tricuspid valves open, and the cycle repeats. 

Finally, the atria relax and collect returning blood when the ventricles are contracting, and in the systole phase—the atria contract in late diastole when the ventricles are fully dilated. 

These pumps never run out of blood because the atria serve as a reservoir for the ventricles and provide a constant flow of blood. As a result, blood is pumped and circulated more efficiently throughout the body – thanks to this coordination.

Conclusion

Joint diastole occurs when the heart’s four chambers are all relaxed. As a result, the heart’s ventricles and atria are in a state of relaxation. Venous blood flows into the auricles during joint diastole. Two-thirds filling of ventricles occurs because the right and left atriums receive blood, opening the right and left atrial valves, allowing blood to flow into the ventricles.

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Frequently asked questions

Get answers to the most common queries related to the NEET UG Examination Preparation.

What happens when all the chambers of the heart are in diastole?

Ans. Following the ventricular systole, the auricles are already in the diasto...Read full

What are cardiomyocytes?

Ans. Cardiomyocytes, the cells that make up the heart muscle, are responsible for pumping the heart. Unlike skeletal...Read full

How does the internal pacemaker work?

Ans. It all begins at the sinoatrial (SA) node, positioned on the right atrium’s inner wall. One or both of th...Read full

What happens in late ventricular diastole?

Ans. The atrial and ventricular chambers are suctioned together during early diastole. The two atrial chambers then ...Read full

Ans. Following the ventricular systole, the auricles are already in the diastole; therefore, all heart chambers are in the diastole.

The greater the fall in pressure in the great arteries during diastole, the more significant the decrease in pressure in the ventricles. As a result, semilunar valves close quickly to prevent blood from flowing backwards.

The second sound, dubbed “dub,” is the result of this. The atria receive blood from the great veins and coronary arteries at this point.

Ans. Cardiomyocytes, the cells that make up the heart muscle, are responsible for pumping the heart. Unlike skeletal muscle cells, which contract involuntarily and rhythmically, cardiomyocytes have intercalated discs, unique to cardiac muscle. Isolated cardiomyocytes will beat if given the proper ratio of nutrients and electrolytes because they are self-stimulated for a while.

Ans. It all begins at the sinoatrial (SA) node, positioned on the right atrium’s inner wall. One or both of the atria contract in unison when electrical charges from the SA node suddenly pulse. As it passes through the atrioventricular (AV) node, the pulse slows for a fraction of a second before continuing to the right atrium and right ventricle walls. They are connected to the AV node’s left and right interventricular septum branches and carry electrical impulses from there. Finally, the Purkinje fibres transport the impulse from the apex of the heart up to the ventricular myocardium, and then the ventricles contract. The ventricles take a short break before starting to pump blood again to ensure a complete ventricle to atrioventricular exchange.

Ans. The atrial and ventricular chambers are suctioned together during early diastole. The two atrial chambers then contract (atrial systole) in late ventricular diastole, creating a rise in blood pressure in both atria and increased blood flow into the ventricles. As seen in Wiggers ‘ illustration, atrial systole begins with an atrial kick. The atrium does not supply as much flow as the ventricles during the cardiac cycle, which gets roughly 80% of the collected blood volume during the active suction period.

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