Q11. What are the four phases of the cardiac cycle and their events?

Background

Topic: Cardiac Cycle

This question tests your understanding of the sequence of events that occur during one heartbeat, including the contraction and relaxation of the atria and ventricles, and the associated changes in blood flow and valve positions.

Key Terms:

• Systole: Contraction phase of the heart chambers.

• Diastole: Relaxation phase of the heart chambers.

• AV valves: Valves between atria and ventricles (tricuspid and mitral).

• Semilunar valves: Valves at the base of the aorta and pulmonary artery.

Key Concepts:

• The cardiac cycle consists of alternating periods of systole and diastole for both atria and ventricles.

• Blood flow is regulated by the opening and closing of heart valves in response to pressure changes.

Step-by-Step Guidance

1. Identify the first phase: Atrial systole, where the atria contract and push blood into the ventricles. AV valves are open, semilunar valves are closed.

2. Next, recognize ventricular systole (first phase): Ventricles begin to contract, AV valves close to prevent backflow, but semilunar valves are still closed.

3. Then, ventricular systole (second phase): Pressure rises, semilunar valves open, and blood is ejected into the arteries.

4. After ejection, ventricular diastole begins: Semilunar valves close, ventricles relax, and blood flows into the atria. AV valves open as pressure drops.

5. Finally, late ventricular diastole: Chambers relax fully, and blood fills the ventricles passively from the atria.

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Q12. Describe the pulmonary and systemic blood circulation.

Background

Topic: Circulatory System

This question tests your knowledge of the two main circuits of blood flow in the body: pulmonary circulation (between heart and lungs) and systemic circulation (between heart and rest of the body).

Key Terms:

• Pulmonary circulation: Carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium.

• Systemic circulation: Carries oxygenated blood from the left ventricle to the body and returns deoxygenated blood to the right atrium.

• Arteries: Vessels carrying blood away from the heart.

• Veins: Vessels carrying blood toward the heart.

Key Concepts:

• The heart acts as a double pump, sending blood to the lungs for oxygenation and then to the rest of the body for nutrient delivery.

• Blood flow direction is determined by pressure gradients and valve positions.

Step-by-Step Guidance

1. Start with pulmonary circulation: Deoxygenated blood enters the right atrium, moves to the right ventricle, and is pumped through the pulmonary arteries to the lungs.

2. In the lungs, blood picks up oxygen and releases carbon dioxide.

3. Oxygenated blood returns to the left atrium via the pulmonary veins.

4. Systemic circulation begins: Oxygenated blood moves from the left atrium to the left ventricle, then is pumped out through the aorta to the body.

5. After delivering oxygen and nutrients, deoxygenated blood returns to the right atrium via the systemic veins.

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