Question

Describe the pressure changes in the atria and ventricles during a cardiac cycle

Answer 1

Answer:

It is a cycle of contraction and relaxation of atria and ventricles.

Explanation:

The cardiac cycle is the sequence of electrical, mechanical, sound and pressure events, related to the flow of blood through the cardiac cavities, the contraction and relaxation of each of them (atria and ventricles), the closure and opening of Valves and noise production. This process takes place in less than a second. The reciprocal of the duration of a cycle is the heart rate (as usually expressed in beats per minute, multiply by 60 if the duration is measured in minutes).

Answer 2

Answer: The  cardiac cycle is the period of time that begins with contraction of the atria and ends with ventricular relaxation. The period of contraction that the heart undergoes while it pumps blood into circulation is called systole. The period of relaxation that occurs as the chambers fill with blood is called diastole.

Pressure differences between the atria and ventricles results in blood flow through the heart, in through the atria and out through the ventricle.

Explanation:

The cardiac cycle comprises a complete relaxation and contraction of both the atria and ventricles, and lasts approximately 0.8 seconds.  At the start of a cycle, the two chambers are in diastole and blood flows passively from the veins into the atria and past the atrioventricular valves into the ventricles. The atria begin to contract (atrial systole), following depolarization of the atria, and pump blood into the ventricles. The ventricles begin to contract (ventricular systole), raising pressure within the ventricles. When ventricular pressure rises above the pressure in the atria, blood flows toward the atria, producing the first heart sound, S1 or lub. As pressure in the ventricles rises above two major arteries, blood pushes open the two semilunar valves and moves into the pulmonary trunk and aorta in the ventricular ejection phase. Following ventricular repolarization, the ventricles begin to relax (ventricular diastole), and pressure within the ventricles drops. As ventricular pressure drops, there is a tendency for blood to flow back into the atria from the major arteries closing the two semilunar valves. The second heart sound, S2 or dub, occurs when the semilunar valves close. When the pressure falls below that of the atria, blood moves from the atria into the ventricles, opening the atrioventricular valves and marking one complete heart (cardiac) cycle.