The Cardiac Cycle

Question 1

The cardiac cycle?

Answer 1

It’s consists of two phases, contraction (systole) and relaxation (diastole).

Question 2

The cardiac cycle order?

Answer 2

• diastole (relaxed): the atria and ventricles relax, the pressure in the aorta / pulmonary artery is greater then on ventricles. Semi lunar valves close, blood flows into the atria and into ventricles from the body and lungs.
• atrial systole (contraction): both the atria contract which increases pressure in the atria, blood is forced into ventricles and AV valves open.
• ventricular systole (contraction): both the ventricles contract which increases pressure in the ventricles. Blood is forced into the pulmonary artery / aorta. The semi lunar valves open.

Question 3

What occurs in the diastole stage?

Answer 3

• the atrioventricular valves open and pressure in the ventricle drops lower than the atria filling the atria and ventricles with blood.
• the semilunar valves are closed and pressure in the aorta is greater than the ventricles and it prevents back flow of blood into ventricles.

Question 4

What occurs in the atrial systole stage?

Answer 4

• the atrioventricular valves are open and pressure in the ventricle drops lower than the atria filling the ventricles with blood.
• the semilunar valves are closed and pressure in the aorta is greater than the ventricles.

Question 5

What occurs in the ventricular systole stage?

Answer 5

• atrioventricular valves are closed and pressure in the ventricle is higher than the atria, it prevents back flow into the atria.
• semilunar valves are open and pressure in the ventricles is greater than the aorta which allows blood flow in aorta.

Question 6

Cardiac output =

Answer 6

Heart rate X stroke volume

Question 7

Heart rate =

Answer 7

 Minutes

Question 8

Stroke volume =

Answer 8

Beats

Question 9

Heart at rest?

Answer 9

The heart is myogenic this means it generates its own electrical impulse. The impulse that it generates spreads throughout the heart and causes it to contract. This is known as the cardiac impulse.

Question 10

Sinoatrial nodes (SAN) fires?

Answer 10

A wave of electrical activity spreads through both atria which causes them to contract. Electrical activity can’t travel beyond the atria due to the atrioventricular septum, often known as the bodies natural pacemaker.

Question 11

Atrioventricular node (AVN) fires?

Answer 11

Electrical activity then spread down the bundle of his and then up through the ventricle walls via the fibres causing the ventricles to contract.