Cardiovascular System – Lecture Set #1

Vocabulary flashcards covering the main structures, proteins, electrophysiology, and functional concepts discussed in the Cardiovascular System lecture.

Cardiovascular System

Body system whose primary role is transport of fuels, gases, hormones, waste, and heat via blood, driven by the heart through blood vessels.

Mean Arterial Pressure (MAP)

Average arterial blood pressure that drives blood through the systemic circulation, critical for homeostasis.

Systemic Circulation

High-pressure circuit that carries oxygen-rich blood from the left heart to the body and returns oxygen-poor blood to the right heart.

Pulmonary Circulation

Low-pressure circuit that carries oxygen-poor blood from the right heart to the lungs and returns oxygen-rich blood to the left heart.

Blood Plasma

Liquid portion (~60 % of blood) composed mostly of water plus ions, glucose, gases, hormones, and plasma proteins.

Formed Elements

Cellular portion of blood including red blood cells, leukocytes, and platelets.

Erythrocytes (Red Blood Cells)

Biconcave, nucleus-free cells packed with hemoglobin; transport O₂, CO₂, and H⁺; lifespan ≈120 days.

Leukocytes (White Blood Cells)

Immune cells that defend the body; make up a small fraction of formed elements.

Platelets

Cell fragments from megakaryocytes that participate in plug formation during hemostasis.

Albumin

Most abundant liver-derived plasma protein; major contributor to colloid osmotic pressure.

Globulins

Plasma proteins that include transport globulins (α,β) and immune antibodies (γ-globulins).

Fibrinogen

Plasma protein converted to fibrin during clotting to stabilize platelet plugs.

Hemostasis

Physiological process that stops bleeding via vascular spasm, platelet plug, and coagulation (fibrin clot).

Atrioventricular (AV) Valves

Valves between atria and ventricles (tricuspid & mitral) that prevent backflow during ventricular contraction.

Semilunar Valves

Valves between ventricles and arteries (pulmonary & aortic) that prevent arterial blood from re-entering ventricles.

Chordae Tendineae

Tendon-like cords that anchor AV valve cusps to papillary muscles, preventing prolapse.

Papillary Muscles

Ventricular muscles that contract with ventricles to tension chordae tendineae and stabilize AV valves.

Fibrous Skeleton of the Heart

Dense connective tissue that electrically isolates atria from ventricles and provides valve anchorage.

Cardiac Myocytes

Striated, branched muscle cells responsible for heart contraction; connected by intercalated discs.

Intercalated Discs

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

Gap Junctions

Channels within intercalated discs allowing direct electrical coupling between adjacent cardiac myocytes.

Desmosomes

Anchoring junctions within intercalated discs that provide strong mechanical attachment between cells.

Autorhythmic Cells

~1 % of cardiac cells that spontaneously generate and conduct action potentials (pacemaking & conductive cells).

Sinoatrial (SA) Node

Primary pacemaker located in the right atrium; initiates each cardiac cycle.

Pacemaker Potential

Slow spontaneous depolarization (Phase 4) in SA-node cells leading to threshold and an action potential.

HCN (If) Channels

Hyperpolarization-activated cyclic nucleotide-gated Na⁺ channels responsible for initial slow depolarization in pacemaker cells.

T-Type Ca²⁺ Channels

Voltage-gated Ca²⁺ channels that contribute to late Phase 4 depolarization in pacemaker cells.

L-Type Ca²⁺ Channels

Voltage-gated Ca²⁺ channels responsible for Phase 0 upstroke in pacemaker cells and plateau phase in myocytes.

Atrioventricular (AV) Node

Node that receives impulses from atria, imposes the AV-nodal delay, and relays signals to ventricles.

AV-Nodal Delay

~100 ms pause in impulse conduction at the AV node that allows ventricles to fill before they contract.

Bundle of His

Fast conductive pathway in the interventricular septum transmitting impulses from AV node to bundle branches.

Purkinje Fibers

Large-diameter conductive fibers that rapidly spread impulses through ventricular myocardium.

Cardiac Action Potential – Phase 0

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

Cardiac Action Potential – Phase 1

Brief initial repolarization caused by transient outward K⁺ efflux.

Cardiac Action Potential – Phase 2 (Plateau)

Prolonged depolarized state (~200 ms) from balanced Ca²⁺ influx via L-type channels and K⁺ efflux via delayed rectifier channels.

Cardiac Action Potential – Phase 3

Repolarization as Ca²⁺ channels inactivate and K⁺ efflux continues through delayed rectifier channels.

Cardiac Action Potential – Phase 4

Resting membrane potential (in myocytes) maintained primarily by K⁺ permeability until the next depolarization.

Dihydropyridine Receptor (DHPR)

L-type Ca²⁺ channel in the sarcolemma that triggers Ca²⁺ entry during Phase 2.

Ryanodine Receptor (RyR)

Ca²⁺ release channel on the sarcoplasmic reticulum that opens in response to incoming Ca²⁺ (CICR).

Ca²⁺-Induced Ca²⁺ Release (CICR)

Process where Ca²⁺ entry via DHPR activates RyR to release more Ca²⁺ from the SR, initiating contraction.

Cardiac Refractory Period

~250 ms period during which a second action potential cannot be initiated, preventing tetanus.

Ohm’s Law for Blood Flow

Flow (Q) equals pressure gradient (ΔP) divided by resistance (R): Q = ΔP/R.

Electrocardiogram (ECG/EKG)

Surface recording of the summed electrical activity of the heart over time.

P-Wave

ECG deflection representing atrial depolarization.

QRS Complex

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

T-Wave

ECG deflection representing ventricular repolarization.

PR Interval

Time from start of P-wave to start of QRS; reflects atrial depolarization plus AV-nodal conduction (0.12–0.22 s).

PR Segment

Flat section from end of P-wave to start of QRS; represents delay between atrial and ventricular depolarization.

QT Interval

Time from start of QRS to end of T-wave; duration of ventricular depolarization and repolarization (0.31–0.41 s).

Colloid Osmotic Pressure

Osmotic pressure generated by plasma proteins (especially albumin) that draws water into the bloodstream.