In the cardiac cycle, when pressure increases while volume remains constant, which phase is this?& x20; - INI-CET EXAM -2025

INI-CET EXAM -2025

Applied Physiology

Easy

Appeared in: INI-CET EXAM -2025

Explanation

Isovolumetric contraction is the initial phase of ventricular systole, occurring right after the atrioventricular (AV) valves close.
During this phase, the ventricles contract as a closed chamber because both the AV valves and the semilunar (aortic/pulmonary) valves are shut.
This contraction against a fixed volume of blood causes a sharp and rapid increase in intraventricular pressure.
The term 'isovolumetric' itself means 'constant volume,' which is the key feature of this phase along with rising pressure.

Option B: During isovolumetric relaxation, the ventricles relax, causing pressure to decrease rapidly, although the volume does remain constant because all valves are closed.
Option C: During rapid ventricular filling, the volume of blood in the ventricles is actively increasing as blood flows in from the atria. Pressure remains low during this phase.
Option D: During ventricular ejection, blood is actively pumped out of the ventricles, so the volume is decreasing, not remaining constant.

Visual 1: Wiggers Diagram. This diagram is essential for understanding the cardiac cycle as it graphically displays the relationship between ventricular pressure, ventricular volume, aortic pressure, atrial pressure, ECG, and heart sounds all on a common time axis. It clearly shows the 'isovolumetric contraction' phase as a vertical line on the pressure-volume loop, indicating a sharp pressure rise with no change in volume.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Phases of the Cardiac Cycle as background academic context rather than a clinical decision trigger.
Understanding isovolumetric contraction is crucial for comprehending cardiac hemodynamics. The pressure generated during this phase must be high enough to overcome the 'afterload' (the pressure in the aorta) to open the aortic valve and eject blood.
In conditions like hypertension, the afterload is high, forcing the left ventricle to generate even greater pressure during isovolumetric contraction. Over time, this can lead to left ventricular hypertrophy (thickening of the heart muscle).
What if a patient has aortic stenosis (narrowing of the aortic valve)? The ventricle must generate an extremely high pressure during isovolumetric contraction to force the stiff valve open, significantly increasing the workload on the heart and prolonging this phase.

How to Approach the Question

First, identify the key conditions given in the question stem: 1) pressure increases, and 2) volume remains constant.
Next, break down the terminology in the options. The prefix 'iso-' means 'same' or 'constant'. 'Volumetric' refers to volume. Therefore, 'isovolumetric' means 'constant volume'.
Evaluate the options based on this breakdown. 'Isovolumetric contraction' implies a contraction (which increases pressure) at a constant volume. 'Isovolumetric relaxation' implies relaxation (which decreases pressure) at a constant volume.
Compare this with the question's conditions. The question asks for increasing pressure and constant volume, which directly matches the definition of 'isovolumetric contraction'.
Eliminate the other options: 'Ventricular filling' involves increasing volume, and 'ventricular ejection' involves decreasing volume.

Concept Tested & Keywords

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