cardiovascular phys

Direction of Blood Flow Through Heart

Right Atrium -> Tricuspid Valve -> Right Ventricle -> Pulmonary Valve -> Pulmonary Arteries -> Lungs -> Pulmonary Veins -> Left Atrium -> Mitral (Bicuspid) Valve -> Left Ventricle -> Aortic Valve -> Aorta -> Systemic Circulation.

Locations of Oxygenated Blood

Pulmonary veins, left atrium, left ventricle, aorta, and systemic arteries/arterioles.

Locations of Deoxygenated Blood

Systemic veins, superior/inferior venae cavae, right atrium, right ventricle, and pulmonary trunk/arteries.

Atrioventricular (AV) vs Semilunar Valves

AV valves (Tricuspid/Mitral) open during diastole and close during systole to prevent backflow into atria. Semilunar valves (Pulmonary/Aortic) open during systole and close during diastole to prevent backflow into ventricles.

AV and Semilunar Valves Simultaneous State

FALSE. AV and semilunar valves can NEVER be open at the same time during any phase of the cardiac cycle.

Isovolumic Ventricular Contraction

Early ventricular systole; all valves closed; ventricular pressure rises rapidly without volume change; ventricular blood volume is at its HIGHEST (EDV ~135 mL); S1 heart sound ("lub") detected.

Isovolumic Ventricular Relaxation

Early ventricular diastole; all valves closed; ventricular pressure falls rapidly without volume change; ventricular blood volume is at its LOWEST (ESV ~65 mL); S2 heart sound ("dub") detected.

End-Diastolic Volume (EDV) vs End-Systolic Volume (ESV)

EDV: Volume of blood in ventricles at end of filling / start of contraction (~135 mL). ESV: Volume of blood remaining in ventricles after ejection (~65 mL).

Stroke Volume (SV) Equation & Calculation

SV = EDV - ESV (e.g., 135 mL - 65 mL = 70 mL/beat).

Cardiac Output (CO) Equation & Calculation

CO = Stroke Volume (SV) x Heart Rate (HR) (e.g., 70 mL/beat x 75 BPM = 5250 mL/min or 5.25 L/min).

Frank-Starling Mechanism

Increased venous return stretches cardiac muscle myocytes, increasing EDV and optimal sarcomere overlap, resulting in increased Stroke Volume.

ECG: P Wave

Represents atrial depolarization, which triggers atrial contraction (systole).

ECG: PR Segment

Represents the slight electrical conduction delay through the AV node, allowing complete ventricular filling.

ECG: QRS Complex

Represents ventricular depolarization (precedes ventricular contraction) and masks atrial repolarization.

ECG: ST Segment

Period when ventricles are fully depolarized and actively contracting (systole).

ECG: T Wave

Represents ventricular repolarization, preceding ventricular relaxation (diastole).

Sinoatrial (SA) Node

The primary pacemaker of the heart that spontaneously initiates electrical action potentials spreading via gap junctions.

Functional Syncytium

Cardiomyocytes connected via intercalated discs (desmosomes + gap junctions), allowing synchronized electrical and mechanical contraction as a single unit.