The Question is from neet-zoology body-fluids-and-circulation cardiac-cycle, and it was created by the author T SAILAJA

Question

During isovolumetric contraction, which of the following statements regarding the pressure changes in the atria, ventricles, and aorta is MOST accurate?

T SAILAJA · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
	**Primary Concept**: Cardiac Cycle - Isovolumetric Contraction
	**Related Topics**: Heart Valves, Pressure-Volume Loop, Wiggers Diagram
	**Prerequisites**: Basic heart anatomy and physiology
## SOLUTION PATHWAY
**Given Information**:
	Isovolumetric contraction phase of the cardiac cycle.
	Need to determine pressure changes in atria, ventricles, and aorta.
**Method & Steps**:
	1. **Ventricular Contraction Begins**: Ventricles begin to contract, increasing ventricular pressure.
		Reasoning: Muscle contraction decreases chamber volume, increasing pressure.
	2. **AV Valves Close**: The rising ventricular pressure exceeds atrial pressure, causing the atrioventricular (AV) valves (mitral and tricuspid) to close.
		Working: This marks the beginning of isovolumetric contraction.  'Isovolumetric' means constant volume – all valves are closed.
		Key Point:  Blood cannot flow in or out of the ventricles during this phase.
	3. **Aortic Valve Remains Closed**:  Initially, the ventricular pressure is still less than the aortic pressure, keeping the aortic valve closed.
		Result:  As the ventricle continues to contract, aortic pressure may fall slightly due to the elastic recoil of the aorta from the previous ejection phase.  Once ventricular pressure surpasses aortic pressure, the aortic valve opens and ejection begins.
		Verification:  The closure of the AV valves produces the first heart sound (S1).  The aortic valve opening marks the end of isovolumetric contraction.
 ## OPTION ANALYSIS
[A] :x: Ventricular pressure rises (correct), atrial pressure rises (incorrect - it falls slightly as ventricular pressure rises and the AV valves close), and aortic pressure rises (incorrect - initially falls slightly then rises sharply when the aortic valve opens).
[B] ✓: Ventricular pressure rises (correct), atrial pressure falls (correct - due to AV valve closure and reduced blood flow from the pulmonary veins), and aortic pressure initially falls slightly (correct - due to aortic elastic recoil) then rises when the aortic valve opens (this part is beyond isovolumetric contraction).
[C] :x: Ventricular pressure falls (incorrect - it rises during contraction), atrial pressure rises (partially correct, atrial pressure rises during ventricular systole after the initial dip when the AV valves close), and aortic pressure falls (partially correct initially, but only until the aortic valve opens).
[D] :x: Ventricular pressure falls (incorrect - it rises), atrial pressure falls (partially correct initially, but then rises during ventricular systole), and aortic pressure rises (incorrect initially, but it rises once the aortic valve opens).
 ## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing isovolumetric contraction with isovolumetric relaxation:  During isovolumetric relaxation, all valves are closed and ventricular pressure falls. 
		2.  Not understanding the sequence of valve closures and openings: Remember that the AV valves close before the aortic valve opens.
	**Quick Tips**:
		1. 'Isovolumetric' means constant volume - no blood is entering or leaving the ventricles.
		2. Visualize the pressure-volume loop or Wiggers Diagram to understand the pressure changes during the cardiac cycle.

T SAILAJA · Answer

Ventricular pressure rises, atrial pressure rises, and aortic pressure rises.

T SAILAJA · Answer

The correct Option is "Ventricular pressure rises, atrial pressure falls, and aortic pressure initially falls slightly."

T SAILAJA · Answer

Ventricular pressure falls, atrial pressure rises, and aortic pressure falls.

T SAILAJA · Answer

Ventricular pressure falls, atrial pressure falls, and aortic pressure rises.

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