Cardiovascular: The Cardiac Cycle and Cardiac Output

These flashcards cover key vocabulary and definitions related to the cardiovascular system, specifically the cardiac cycle and cardiac output.

Heart Rate (HR)

The number of cardiac cycles (beats) per minute.

Stroke Volume (SV)

The volume of blood ejected into the artery during each cardiac cycle (mL/beat).

End Diastolic Volume (EDV)

The volume of blood in the ventricle at the end of diastole (120 mL at rest).

End Systolic Volume (ESV)

The volume of blood remaining in the ventricle after contraction (approximately 50 mL at rest).

Ejection Fraction

The percentage of EDV that is ejected during the contraction phase.

Cardiac Output (CO)

The volume of blood moved through the heart into the systemic circuit in a given time (mL/min). CO = HR x SV.

Isometric Contraction

A phase where the heart ventricles contract with no change in volume; all valves are closed.

Isometric Relaxation

A phase where the heart ventricles relax with no change in volume; all valves are closed.

Preload

The degree of stretch of the ventricular myocardium at the end of diastole, influenced by EDV.

Afterload

The pressure the ventricles must overcome to eject blood, influenced by arterial pressure.

Contractility

The strength of heart muscle contraction for a given amount of preload.

Frank-Starling Law

An increase in EDV results in an increase in stroke volume due to stretching of the ventricles.

Venous Return

The volume of blood that returns to the right atrium during the cardiac cycle.

Filling Time

The duration of ventricular diastole, which determines how long the AV valves are open.

Atrial Reflex

Adjustments in heart rate in response to increases in venous return as detected by stretch receptors in the atrium.