Cardiac Cycle Flashcards
(18 cards)
What is the cardiac cycle?
One complete heartbeat (contraction and relaxation of the heart).
What are the two main phases of the cardiac cycle?
Systole (when the heart muscle contracts) and Diastole (when the heart muscle relaxes).
What occurs during atrial systole?
The top chambers of the heart (atria) squeeze, pushing blood into the bottom chambers (ventricles).
What occurs during ventricular systole?
The bottom chambers of the heart (ventricles) squeeze, pumping blood out to the lungs and the rest of the body.
What occurs during atrial diastole?
The top chambers of the heart (atria) relax and start to fill with blood coming back from the body and lungs.
What occurs during ventricular diastole?
The bottom chambers of the heart (ventricles) relax and start to fill with blood from the atria.
What is isovolumetric contraction?
The ventricles start to squeeze, but all the valves are closed, so no blood is moving yet.
What is isovolumetric relaxation?
The ventricles finish squeezing and start to relax, but all the valves are still closed for a brief moment.
What causes the opening of the atrioventricular (AV) valves?
When the pressure in the top chambers (atria) becomes higher than the pressure in the bottom chambers (ventricles).
What causes the closing of the AV valves?
When the pressure in the bottom chambers (ventricles) becomes higher than the pressure in the top chambers (atria).
What causes the opening of the semilunar valves?
When the pressure in the bottom chambers (ventricles) becomes higher than the pressure in the arteries leading out of the heart.
What causes the closing of the semilunar valves?
When the pressure in the arteries becomes higher than the pressure in the bottom chambers (ventricles).
What is the role of the sinoatrial (SA) node in the cardiac cycle?
It’s the heart’s natural pacemaker, sending out electrical signals that tell the heart muscle to contract and start each heartbeat.
What is the role of the atrioventricular (AV) node in the cardiac cycle?
It receives the electrical signal from the SA node, delays it briefly, and then sends it down to the ventricles, ensuring the atria contract before the ventricles.
What are the ‘lub’ and ‘dub’ sounds of the heartbeat caused by?
The ‘lub’ sound is caused by the closing of the AV valves, and the ‘dub’ sound is caused by the closing of the semilunar valves.
What is stroke volume?
The amount of blood pumped out by one of the bottom chambers (ventricles) with each heartbeat.
What is heart rate?
The number of times the heart beats per minute.
How is cardiac output calculated?
Cardiac Output = Stroke Volume x Heart Rate.
