Question

In p-v graph of cardiac cycle S3 and S4 will be heard between which points?

Answer 1

Answer:

Explanation:

DESIGN AND PHYSIOLOGY OF THE HEART | Physiology of Cardiac Pumping

A.P. Farrell, in Encyclopedia of Fish Physiology, 2011

The Flow Events: Cardiac Chamber Filling and Emptying

Figure 1 illustrates the sequential filling and emptying of the cardiac chambers during a cardiac cycle.

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Figure 1. A schematic diagram of the three main phases of filling and emptying of four cardiac chambers of the fish heart. (a) Both the atrium and ventricle are filling due the venous blood pressure. (b) The atrium contracts (as shown by the small arrows), further expanding and completing the filling of the ventricle. (c) The ventricle contracts, ejecting fluid into the bulbus arteriosus. At the same time, the atrium begins to fill.

The cardiac cycle begins with the atrium and ventricle in a relaxed state. During diastole, blood flowing from central veins fills the atrium and partially fills the ventricle, passing through the sinus venosus, the sino-atrial (SA) canal and the atrio-ventricular (AV) canal. Atrial contraction (atrial systole) then ejects blood from the atrium and into the ventricle, which is still in diastole, and this completes ventricular filling. The contributions of these two phases of ventricular filling vary among species, with sometimes only ∼50% occurring via atrial contraction. In addition, the contribution of passive ventricular filling may decrease at high heart rates when the diastole is shorter.

Atrial relaxation (atrial diastole) occurs while the ventricle is contracting (ventricular systole). However, before ventricular contraction starts, the propagation of the action potential from the atrium is briefly delayed in the AV canal. This AV delay ensures that blood has sufficient time to move from the atrium and complete ventricular filling. Ventricular contraction ejects blood into the outflow tract past an opened bulbo-ventricular (BV) valve. The cardiac cycle is completed when the ventricle relaxes (ventricular diastole).