NEET BIOLOGY

Detailed explanation-1: -At the start of atrial systole, the ventricles are normally filled with approximately 70–80 percent of their capacity due to inflow during diastole. Atrial contraction, also referred to as the “atrial kick, ” contributes the remaining 20–30 percent of filling (see the image below).

Detailed explanation-2: -Approximately 80% (80 percent) of ventricular filling occurs passively before atrial contraction (or atrial systole). The remaining 20 percent ventricular filling occurs after the beginning of atrial systole.

Detailed explanation-3: -As a result of atrial contraction, much of the remaining atrial blood is ejected through the AV valves into the ventricles. At rest, this atrial ‘kick’ accounts for only 10% of ventricular filling: 90% of the blood flows into the ventricle passively.

Detailed explanation-4: -In the systole phase, blood is forced to flow from the two atria into their respective ventricles as the atrial muscles contract due to the depolarization of the atria.

Detailed explanation-5: -The two atrioventricular valves, the tricuspid and mitral valves, are both open, so blood flows unimpeded from the atria and into the ventricles. Approximately 70–80 percent of ventricular filling occurs by this method.