The contraction phase of heart which leads to the ejection of blood into the arteries is called \ \ \ . - MP NHM CHO-2024 (Shift-1)

MP NHM CHO-2024 (Shift-1)

Applied Physiology

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Appeared in: MP NHM CHO-2024 (Shift-1)

Explanation

Systole is the phase of the cardiac cycle when the heart muscle contracts.
Specifically, ventricular systole involves the contraction of the ventricles.
This contraction increases pressure inside the ventricles, forcing the aortic and pulmonary valves to open.
The opening of these valves allows blood to be ejected from the ventricles into the aorta and pulmonary artery.

Option A: Ventricular repolarization is an electrical event (T wave on ECG) that signals the start of ventricular relaxation (diastole), not contraction.
Option B: Atrial depolarization is an electrical event (P wave on ECG) that causes the atria to contract, which helps fill the ventricles. It does not cause ejection of blood into the arteries.
Option D: Diastole is the relaxation phase of the cardiac cycle when the heart chambers fill with blood. It is the opposite of systole.

Visual 1: Diagram of the Cardiac Cycle. A diagram showing the two main phases, systole (contraction/ejection) and diastole (relaxation/filling), with the corresponding valve positions and blood flow direction.
Visual 2: ECG Waveform. An image of a normal ECG trace, labeling the P wave (atrial depolarization), QRS complex (ventricular depolarization), and T wave (ventricular repolarization) to differentiate electrical events from mechanical phases.

Clinical Relevance

Nursing practice connection: Knowing Cardiac Cycle Phases helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding systole and diastole is fundamental for measuring and interpreting blood pressure. The systolic pressure is the peak pressure in the arteries during ventricular contraction, and the diastolic pressure is the lowest pressure during ventricular relaxation.
Abnormalities in systole or diastole are central to many heart conditions. For example, heart failure can be classified as systolic dysfunction (impaired contraction and ejection) or diastolic dysfunction (impaired relaxation and filling).
What if? If a patient has a very high heart rate (tachycardia), the duration of diastole shortens significantly more than systole. This can compromise ventricular filling time, leading to decreased stroke volume and potentially reduced cardiac output, which can cause symptoms like dizziness or fainting.

How to Approach the Question

First, identify the key terms in the question: 'contraction phase' and 'ejection of blood into arteries'.
Recall the two main phases of the cardiac cycle: systole (contraction) and diastole (relaxation).
Directly match the term 'contraction phase' with 'systole'.
Consider the other options. 'Diastole' is the opposite (relaxation). 'Ventricular repolarization' and 'atrial depolarization' are electrical events that trigger mechanical actions, not the mechanical actions themselves.
Eliminate the incorrect options based on these definitions to confirm that systole is the only term that describes the mechanical contraction and ejection of blood.

Concept Tested & Keywords

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