Cardiac Output & Stroke Volume – Key Vocabulary

25 vocabulary flashcards summarizing the essential terms and definitions related to cardiac output, stroke volume, and their regulatory factors as presented in the lecture.

Cardiac Output (CO)

Volume of blood ejected by the left ventricle in one minute; calculated as Heart Rate × Stroke Volume and expressed in L/min.

Stroke Volume (SV)

Volume of blood ejected by the left ventricle with each heartbeat; measured in mL/beat.

Heart Rate (HR)

Number of heartbeats per minute; one of the two variables that determine cardiac output.

End-Diastolic Volume (EDV)

Amount of blood in a ventricle at the end of filling (diastole); determines preload.

End-Systolic Volume (ESV)

Amount of blood remaining in a ventricle after contraction (systole).

Preload

The pressure (tension) on the ventricular wall at the end of diastole, produced by EDV; affects sarcomere stretch and SV.

Afterload

Arterial pressure the ventricle must overcome to open the semilunar valve and eject blood; higher afterload lowers SV.

Contractility

Change in ventricular force of contraction for a given EDV, produced mainly by sympathetic stimulation (norepinephrine/epinephrine).

Frank–Starling Effect

Intrinsic property whereby increased EDV stretches cardiac muscle, optimizes sarcomere length, and raises stroke volume.

Intrinsic Control

Regulation originating within the heart itself (e.g., Frank–Starling effect) independent of neural/hormonal input.

Extrinsic Control

Regulation of cardiac function by external signals such as autonomic nerves and circulating hormones.

Sympathetic Activity

Autonomic input that raises heart rate and contractility via norepinephrine (nerve) and epinephrine (blood).

Norepinephrine

Sympathetic neurotransmitter that increases heart rate and contractility.

Epinephrine

Adrenal medulla hormone that mirrors norepinephrine’s cardiac effects when released into the blood.

Venous Return

Volume of blood returning to the right atrium per minute; major determinant of EDV and preload.

Filling Time

Interval between heartbeats during which ventricles fill; shortened when heart rate rises.

Length–Tension Relationship

Principle that muscle force varies with sarcomere length; basis for the Frank–Starling effect in the heart.

Sarcomere

Contractile unit of muscle fibers; its length changes with ventricular stretch and influences force output.

Isovolumetric Contraction

Early phase of systole when ventricles contract with no volume change while building pressure to open semilunar valves.

Fight-or-Flight Response

Sympathetic reflex that raises HR and SV to boost cardiac output during stress or exercise.

Arterial Blood Pressure

Pressure within large arteries (e.g., aorta); major component of afterload.

Hypertension

Chronically elevated arterial pressure that increases afterload and can reduce stroke volume.

Heart Failure

Condition of weakened cardiac muscle where even normal afterload markedly lowers stroke volume.

Cardiac Cycle

Sequence of mechanical and electrical events in one heartbeat, including diastole and systole.

Blood Volume

Total quantity of blood in circulation (~5 L in an average adult male); equals average resting cardiac output per minute.