Cardiac Cycle Flashcards
(54 cards)
What is the cardiac cycle?
The sequence of alternating contraction and relaxation of the atria and ventricles to pump blood throughout the body.
When does the cardiac cycle start and end?
It starts at the beginning of one heartbeat and ends at the beginning of another.
At what gestational week does the heart begin to contract?
The 4th gestational week.
What are the two main phases of the cardiac cycle?
Diastole (filling phase) and systole (pumping phase).
What is the function of the sinoatrial (SA) node?
It acts as the pacemaker of the heart, setting the rhythm of contraction.
Where is the SA node located?
Near the opening of the superior vena cava on the superior lateral wall of the right atrium.
What is the atrioventricular (AV) node’s primary function?
It delays impulse transmission, allowing the atria to contract before the ventricles depolarize.
Where is the AV node located?
Medial and posterior to the tricuspid valve.
What is the bundle of His?
A network of fibers that transmit electrical signals from the AV node to the ventricles.
What are Purkinje fibers?
Fibers that supply the ventricular myocardium, ensuring coordinated contraction.
What happens during atrial diastole?
The atria relax and passively fill with blood from the veins.
What happens when atrial pressure exceeds ventricular pressure?
The atrioventricular valves open, allowing blood to flow into the ventricles.
What initiates atrial systole?
An action potential from the SA node.
What is the purpose of atrial systole?
To push residual blood from the atria into the ventricles.
What happens during early ventricular diastole?
Both atrioventricular and semilunar valves are closed, and intraventricular pressure falls.
What is isovolumetric relaxation?
A phase in early ventricular diastole where no blood flows into or out of the ventricles.
What is diastasis?
The middle phase of ventricular diastole, where passive filling slows before atrial contraction.
What is the end-diastolic volume (preload)?
The total volume of blood in the ventricles at the end of diastole.
What happens during ventricular systole?
The ventricles contract and eject blood into the arteries.
What is isovolumetric contraction?
The phase in ventricular systole where pressure builds, but no blood is ejected.
When do the semilunar valves open?
When ventricular pressure exceeds arterial pressure.
What is the ejection phase?
The period during ventricular systole when blood is pushed into the arteries.
What is end-systolic volume (afterload)?
The volume of blood remaining in the ventricle after contraction (~40-50 mL).
What is stroke volume?
The amount of blood ejected from the ventricle per heartbeat.
