Cardiovascular System – Lecture Set #1

Vocabulary flashcards summarizing key terms, structures, and physiological concepts from the Cardiovascular System Lecture Set #1.

Cardiovascular System

Body system responsible for transport, homeostasis, and protection via blood, heart, and vasculature.

Systemic Circulation

Circuit that carries oxygen-rich blood from the left heart to the body and returns oxygen-poor blood to the right atrium.

Pulmonary Circulation

Circuit that carries oxygen-poor blood from the right heart to the lungs and returns oxygen-rich blood to the left atrium.

Blood

Transport medium composed of plasma and formed elements (erythrocytes, leukocytes, platelets).

Plasma

Liquid portion (~60 % of blood) mostly water, containing ions, glucose, gases, proteins (albumin, globulins, fibrinogen).

Albumin

Abundant liver protein that helps maintain colloid osmotic pressure of plasma.

Globulins

Plasma proteins; α and β globulins act as transport proteins, γ globulins are immunoglobulins (antibodies).

Fibrinogen

Plasma clotting protein that is converted to fibrin during clot formation.

Erythrocyte

Red blood cell; biconcave, anucleate cell packed with hemoglobin for O2/CO2 transport.

Leukocyte

White blood cell; part of immune defense, present in buffy coat.

Platelet

Megakaryocyte fragment that participates in hemostatic plug formation at vessel injury.

Hemostasis

Process that stops bleeding via vasoconstriction, platelet plug, and clot (fibrin) formation.

Mean Arterial Pressure (MAP)

Average arterial pressure that drives blood flow and supports homeostasis.

Ohm’s Law for Circulation

Blood flow = ΔP / R, where ΔP is pressure gradient and R is resistance.

Heart

Muscular pump that generates pressure to drive blood through pulmonary and systemic circuits.

Atrium

Upper chamber of heart that receives blood from veins.

Ventricle

Lower chamber of heart that pumps blood into arteries.

Fibrous Skeleton

Connective tissue barrier that electrically insulates atria from ventricles and anchors valves and muscle.

Atrioventricular (AV) Valve

Valve between atrium and ventricle; prevents backflow into atria (e.g., tricuspid, mitral).

Semilunar Valve

Valve between ventricle and artery (pulmonary or aortic); prevents backflow into ventricles.

Cardiac Myocyte

Striated, branching muscle cell joined by intercalated discs; performs contractile work of heart.

Intercalated Disc

Specialized junction containing gap junctions and desmosomes that electrically and mechanically link cardiac cells.

Autorhythmic Cell

Non-contractile cardiac cell (≈1 %) that spontaneously generates or conducts action potentials.

Sinoatrial (SA) Node

Primary pacemaker located in right atrium that initiates each heartbeat.

Pacemaker Potential

Slow depolarization (Phase 4) of autorhythmic cells caused by Na⁺ (If), Ca²⁺ influx, and reduced K⁺ efflux, leading to spontaneous action potentials.

HCN (If) Channel

Hyperpolarization-activated cyclic nucleotide-gated channel carrying the ‘funny’ Na⁺ current in pacemaker cells.

Atrioventricular (AV) Node

Node that slows impulse conduction (AV-nodal delay) before it enters ventricles.

AV-Nodal Delay

~100 ms pause at AV node allowing atria to complete contraction before ventricles contract.

Bundle of His

Fast-conducting pathway through interventricular septum that carries impulses from AV node to bundle branches.

Purkinje Fibers

Rapidly conducting fibers that distribute impulse to ventricular myocardium for coordinated contraction.

Cardiac Action Potential

Five-phase electrical event (0–4) in myocytes featuring rapid depolarization, brief repolarization, plateau, and final repolarization.

Phase 0 (Cardiac AP)

Rapid depolarization due to voltage-gated Na⁺ (and some Ca²⁺) influx.

Phase 1 (Cardiac AP)

Brief repolarization from transient K⁺ efflux via Ito channels.

Phase 2 (Plateau)

~200 ms balance of Ca²⁺ influx through L-type channels and K⁺ efflux through delayed rectifier channels.

Phase 3 (Repolarization)

Return to resting potential as Ca²⁺ channels inactivate and K⁺ efflux continues.

Phase 4 (Resting)

Resting membrane potential maintained mainly by K⁺ conductance in myocytes.

Calcium-Induced Calcium Release (CICR)

Process where Ca²⁺ entering via L-type channels triggers further Ca²⁺ release from SR through ryanodine receptors (RyRs).

Cardiac Refractory Period

~250 ms period during which new AP cannot be initiated, preventing tetanus.

Electrocardiogram (ECG)

Surface recording of summed cardiac electrical activity.

P-Wave

ECG deflection representing atrial depolarization.

QRS Complex

ECG waveform representing ventricular depolarization (and atrial repolarization hidden).

T-Wave

ECG deflection representing ventricular repolarization.

PR Interval

Start of P to start of QRS (0.12–0.22 s); indicates conduction time from atrial to ventricular depolarization.

PR Segment

End of P to start of QRS; reflects AV-nodal delay.

QT Interval

Start of QRS to end of T (0.31–0.41 s); total time of ventricular depolarization and repolarization, inverse to heart rate.

Cardiovascular System

Body system responsible for transport, homeostasis, and protection via blood, heart, and vasculature.

Systemic Circulation

Circuit that carries oxygen-rich blood from the left heart to the body and returns oxygen-poor blood to the right atrium.

Pulmonary Circulation

Circuit that carries oxygen-poor blood from the right heart to the lungs and returns oxygen-rich blood to the left atrium.

Blood

Transport medium composed of plasma and formed elements (erythrocytes, leukocytes, platelets).

Plasma

Liquid portion (~60 % of blood) mostly water, containing ions, glucose, gases, proteins (albumin, globulins, fibrinogen).

Albumin

Abundant liver protein that helps maintain colloid osmotic pressure of plasma.

Globulins

Plasma proteins; α and β globulins act as transport proteins, γ globulins are immunoglobulins (antibodies).

Fibrinogen

Plasma clotting protein that is converted to fibrin during clot formation.

Erythrocyte

Red blood cell; biconcave, anucleate cell packed with hemoglobin for O2/CO2 transport.

Leukocyte

White blood cell; part of immune defense, present in buffy coat.

Platelet

Megakaryocyte fragment that participates in hemostatic plug formation at vessel injury.

Hemostasis

Process that stops bleeding via vasoconstriction, platelet plug, and clot (fibrin) formation.

Mean Arterial Pressure (MAP)

Average arterial pressure that drives blood flow and supports homeostasis.

Ohm’s Law for Circulation

Blood flow = ΔP / R, where ΔP is pressure gradient and R is resistance.

Heart

Muscular pump that generates pressure to drive blood through pulmonary and systemic circuits.

Atrium

Upper chamber of heart that receives blood from veins.

Ventricle

Lower chamber of heart that pumps blood into arteries.

Fibrous Skeleton

Connective tissue barrier that electrically insulates atria from ventricles and anchors valves and muscle.

Atrioventricular (AV) Valve

Valve between atrium and ventricle; prevents backflow into atria (e.g., tricuspid, mitral).

Semilunar Valve

Valve between ventricle and artery (pulmonary or aortic); prevents backflow into ventricles.

Cardiac Myocyte

Striated, branching muscle cell joined by intercalated discs; performs contractile work of heart.

Intercalated Disc

Specialized junction containing gap junctions and desmosomes that electrically and mechanically link cardiac cells.

Autorhythmic Cell

Non-contractile cardiac cell (≈1 %) that spontaneously generates or conducts action potentials.

Sinoatrial (SA) Node

Primary pacemaker located in right atrium that initiates each heartbeat.

Pacemaker Potential

Slow depolarization (Phase 4) of autorhythmic cells caused by Na⁺ (If), Ca²⁺ influx, and reduced K⁺ efflux, leading to spontaneous action potentials.

HCN (If) Channel

Hyperpolarization-activated cyclic nucleotide-gated channel carrying the ‘funny’ Na⁺ current in pacemaker cells.

Atrioventricular (AV) Node

Node that slows impulse conduction (AV-nodal delay) before it enters ventricles.

AV-Nodal Delay

~100 ms pause at AV node allowing atria to complete contraction before ventricles contract.

Bundle of His

Fast-conducting pathway through interventricular septum that carries impulses from AV node to bundle branches.

Purkinje Fibers

Rapidly conducting fibers that distribute impulse to ventricular myocardium for coordinated contraction.

Cardiac Action Potential

Five-phase electrical event (0–4) in myocytes featuring rapid depolarization, brief repolarization, plateau, and final repolarization.

Phase 0 (Cardiac AP)

Rapid depolarization due to voltage-gated Na⁺ (and some Ca²⁺) influx.

Phase 1 (Cardiac AP)

Brief repolarization from transient K⁺ efflux via Ito channels.

Phase 2 (Plateau)

~200 ms balance of Ca²⁺ influx through L-type channels and K⁺ efflux through delayed rectifier channels.

Phase 3 (Repolarization)

Return to resting potential as Ca²⁺ channels inactivate and K⁺ efflux continues.

Phase 4 (Resting)

Resting membrane potential maintained mainly by K⁺ conductance in myocytes.

Calcium-Induced Calcium Release (CICR)

Process where Ca²⁺ entering via L-type channels triggers further Ca²⁺ release from SR through ryanodine receptors (RyRs).

Cardiac Refractory Period

~250 ms period during which new AP cannot be initiated, preventing tetanus.

Electrocardiogram (ECG)

Surface recording of summed cardiac electrical activity.

P-Wave

ECG deflection representing atrial depolarization.

QRS Complex

ECG waveform representing ventricular depolarization (and atrial repolarization hidden).

T-Wave

ECG deflection representing ventricular repolarization.

PR Interval

Start of P to start of QRS (0.12–0.22 s); indicates conduction time from atrial to ventricular depolarization.

PR Segment

End of P to start of QRS; reflects AV-nodal delay.

QT Interval

Start of QRS to end of T (0.31–0.41 s); total time of ventricular depolarization and repolarization, inverse to heart rate.