NEET2026BiologyChapterActual
Read the following statements and select the incorrect one regarding the human cardiac cycle.
Options
- AThe first heart sound (lub) is associated with the closure of the tricuspid and bicuspid valves.
- BAtrial systole accounts for the flow of approximately 30 percent of the total blood into the ventricles.
- CThe semilunar valves open when the ventricular pressure falls below the pressure in the aorta and pulmonary ar
- DThe action potential generated by the sino-atrial node (SAN) causes simultaneous contraction of both the atria
Correct answer
C. The semilunar valves open when the ventricular pressure falls below the pressure in the aorta and pulmonary ar
Step-by-step solution
The semilunar valves open when the ventricular pressure exceeds the pressure in the aorta and pulmonary artery, allowing blood to be pumped from the ventricles into these vessels. When the ventricular pressure falls below the pressure in the aorta and pulmonary artery, the semilunar valves close to prevent the backflow of blood into the ventricles, producing the second heart sound (dub). The first heart sound (lub) is produced by the closure of the tricuspid and bicuspid valves during ventricular systole. During jo