The diagram given below represents a section of the human heart. Answer the questions that follow: The diagram given below represents a section of the human heart. Answer the questions that follow:
Which parts of heart are in the diastolic phase? Give a reason to support your answer.
Topic: Ventricular diastole
Answer
The VENTRICLES are in the diastolic phase.
Reason: the arrows in the diagram show blood flowing FROM THE ATRIA INTO THE VENTRICLES, which means the tricuspid and bicuspid (atrioventricular) valves are OPEN. Blood can only enter the ventricles when the pressure within them has fallen — that is, when they are relaxed. So the ventricles are in diastole.
Give the answer AND the visible reason — the reason must describe what can be SEEN in the diagram, not what you remember about the cardiac cycle.
SYSTOLE means contraction, DIASTOLE means relaxation.
THE VALVE POSITIONS ARE THE PROOF, because they are OPPOSITE in the two phases: VENTRICULAR DIASTOLE — AV valves OPEN (blood entering), semilunar valves CLOSED VENTRICULAR SYSTOLE — AV valves CLOSED, semilunar valves OPEN (blood leaving)
The single rule that decides every valve question: blood moves from HIGH pressure to LOW, and a valve opens in the direction of flow and closes against it.