Cardiac Cycle Mechanics Lecture

Vocabulary flashcards reviewing essential terms and principles related to the mechanical aspects of the cardiac cycle as discussed in the lecture.

Cardiac Cycle

The complete sequence of electrical and mechanical events occurring in one heartbeat, including atrial contraction, ventricular contraction, and the relaxation period between beats.

Systole

The phase of the cardiac cycle during which a heart chamber contracts, decreasing its volume and raising its internal pressure.

Diastole

The phase of the cardiac cycle during which a heart chamber relaxes, increasing its volume and lowering its internal pressure.

Atria (sing. Atrium)

The two upper heart chambers that receive blood from the veins and help fill the ventricles.

Ventricles

The two lower heart chambers whose contractions propel blood through the pulmonary and systemic circuits.

Poiseuille’s (Poussouet’s) Law (simplified)

Fluid (blood) flows from regions of higher pressure to regions of lower pressure; flow stops if no pressure gradient exists.

Boyle’s Law (cardiac application)

In a closed chamber, pressure varies inversely with volume: decreasing chamber volume raises pressure, increasing volume lowers pressure.

Pressure Gradient

The difference in fluid pressure between two points that drives blood flow from high to low pressure.

Atrioventricular (AV) Valve

One-way valve between an atrium and its ventricle (tricuspid on the right, mitral/bicuspid on the left) that prevents backflow into the atria when ventricles contract.

Semilunar (SL) Valve

One-way valve between a ventricle and its connecting artery (pulmonary and aortic) that prevents arterial blood from re-entering the heart when ventricles relax.

Isovolumetric Contraction

The initial part of ventricular systole when all valves are closed; ventricular pressure rises rapidly while volume stays constant.

Ventricular Ejection

The second part of ventricular systole in which rising ventricular pressure opens the semilunar valves and blood is expelled into the arteries.

Isovolumetric Relaxation

The early part of ventricular diastole when all valves are closed; ventricular pressure falls rapidly while volume remains unchanged.

Ventricular Filling

Phase of ventricular diastole during which the AV valves are open and blood enters the ventricles from the atria.

Passive Filling

Portion of ventricular filling that occurs while all chambers are relaxed, accounting for ~80 % of ventricular volume.

Active Filling (Atrial Kick)

Portion of ventricular filling produced by atrial contraction that contributes the final ~20 % of ventricular blood volume.

SA (Sinoatrial) Node

The heart’s natural pacemaker that initiates each cardiac cycle by generating an electrical impulse across the atria.

Pulmonary Circuit

Pathway in which the right ventricle pumps deoxygenated blood to the lungs and returns oxygenated blood to the left atrium.

Systemic Circuit

Pathway in which the left ventricle pumps oxygenated blood through the body and returns deoxygenated blood to the right atrium.