The Circulatory System: The Heart – Key Vocabulary (Chapter 19)

Vocabulary flashcards covering major terms and concepts from the lecture notes on the heart and cardiovascular system.

Pulmonary circuit

Right side of the heart; carries blood to the lungs for gas exchange and back to the heart.

Systemic circuit

Left side of the heart; supplies oxygenated blood to all body tissues and returns it to the heart.

Pericardium

Double-walled sac that encloses the heart; allows beating with minimal friction and prevents excessive expansion.

Parietal pericardium

Outer layer of the pericardial sac.

Visceral pericardium (epicardium)

Serous membrane covering the heart.

Pericardial cavity

Space inside the pericardial sac filled with 5 to 30 mL of pericardial fluid.

Endocardium

Smooth inner lining of the heart and blood vessels; covers valve surfaces and is continuous with endothelium.

Epicardium

Visceral pericardium; serous membrane covering the heart.

Myocardium

Layer of cardiac muscle responsible for contraction; muscle spirals to wring the heart; thicker in ventricles.

Fibrous skeleton of the heart

Framework of collagenous and elastic fibers; provides structural support, valve attachment, and electrical insulation.

Atria

Two superior chambers that receive blood returning to the heart; have auricles; thin-walled.

Ventricles

Two inferior chambers that pump blood into arteries.

Interatrial septum

Wall that separates the atria.

Interventricular septum

Muscular wall that separates the ventricles.

Atrioventricular (AV) valves

Valves between the atria and ventricles; right AV valve is tricuspid; left AV valve is mitral.

Tricuspid valve

Right AV valve with three cusps.

Mitral valve (bicuspid)

Left AV valve with two cusps.

Chordae tendineae

Tendinous cords connecting AV valves to papillary muscles to prevent inversion during ventricular contraction.

Papillary muscles

Muscles attached to chordae; anchor valves and coordinate contraction; distribute stress.

Semilunar valves

Valves that control flow into the great arteries; open and close due to blood flow and pressure.

Pulmonary semilunar valve

Valve between the right ventricle and the pulmonary trunk.

Aortic semilunar valve

Valve between the left ventricle and the aorta.

Coronary circulation

5% of blood pumped by the heart; about 250 mL/min; nourishes the myocardium.

Right coronary artery (RCA)

Branch off the ascending aorta; supplies the right atrium, SA node, and right ventricle.

Left coronary artery (LCA)

Branches include the anterior interventricular (LAD) and circumflex; supplies left atrium and ventricles.

Anterior interventricular artery (LAD)

Supplies both ventricles and the anterior two-thirds of the interventricular septum.

Circumflex artery

Curves around the left side of the heart; supplies left atrium and posterior wall of the left ventricle.

Posterior interventricular artery

Supplies the posterior walls of the ventricles; branch of the RCA.

Coronary sinus

Main venous drainage into the right atrium; receives great cardiac vein, posterior interventricular vein, left marginal veins.

Thebesian veins

Small veins that drain coronary blood directly into heart chambers.

Angina pectoris

Chest pain from partial obstruction of coronary blood flow; ischemia with lactate production.

Myocardial infarction (MI)

Sudden death of a patch of myocardium due to prolonged obstruction of coronary blood flow.

Conduction system

Internal pacemaker and nerve-like pathways coordinating heartbeat.

Sinoatrial (SA) node

Modified cardiomyocytes; natural pacemaker; initiates heartbeat; located in the right atrium.

Atrioventricular (AV) node

Electrical gateway to the ventricles; located near the right AV valve; part of the conduction pathway.

Bundle of His (AV bundle)

Pathway that splits into right and left bundle branches; conducts impulses to the ventricles.

Subendocardial conducting network

Network distributing excitation through the ventricular myocardium.

Electrocardiogram (ECG/EKG)

Record of the composite electrical activity of nodal and myocardial cells.

P wave

Atrial depolarization and onset of atrial systole.

QRS complex

Ventricular depolarization; mask of ventricular excitation.

T wave

Ventricular repolarization and relaxation.

Isovolumetric contraction

Phase where ventricles contract with all valves closed; volume remains the same.

Ventricular ejection

Phase when ventricular pressure exceeds arterial pressure; semilunar valves open.

End-diastolic volume (EDV)

Volume in the ventricles at the end of diastole; about 130 mL.

End-systolic volume (ESV)

Volume remaining in the ventricles after systole; about 60 mL.

Stroke volume (SV)

Volume ejected by each ventricle per beat; about 70 mL.

Cardiac output (CO)

Volume ejected by each ventricle per minute; CO = heart rate × SV; about 4–6 L/min at rest.

Heart rate (HR)

Number of heartbeats per minute; typical resting ~70–80 bpm; can be tachycardic or bradycardic.

Chronotropic effects

Factors that raise or lower heart rate; autonomic nerves, hormones, electrolytes.

Norepinephrine (NE)

Sympathetic neurotransmitter; increases heart rate and contraction by increasing Ca2+ influx.

Acetylcholine (ACh)

Parasympathetic transmitter; slows heart rate by opening K+ channels in nodal cells.

Vagal tone

Baseline parasympathetic effect that keeps resting heart rate around 70–80 bpm.

Baroreceptors

Pressure sensors in the aorta and carotids; regulate heart rate via reflexes.

Chemoreceptors

Sensors of pH, CO2, and O2; influence heart rate especially during metabolic changes.

Preload

Tension in ventricular myocardium just before contraction; related to EDV.

Frank-Starling law

SV is proportional to EDV; the more the ventricle is stretched, the stronger it contracts.

Contractility

Intrinsic strength of cardiac muscle contraction; positive and negative inotropes.

Afterload

All forces opposing ejection of blood from the ventricle; largely arterial pressure.

Digitalis (foxglove)

Drug that increases intracellular Ca2+ to strengthen contraction; used in heart failure.

Congestive heart failure (CHF)

Failure of either ventricle to eject blood effectively; leads to edema.

Atherosclerosis

Hardening of arteries due to plaques (atheromas) restricting blood flow.

LDL (low-density lipoprotein)

Cholesterol-carrying particles; high levels with defective receptors raise CAD risk.

Coronary bypass surgery

Surgical revascularization using veins or arteries to bypass blocked coronary arteries.

Balloon angioplasty

Procedure to open narrowed arteries with a balloon catheter.

Stent

Mesh tube inserted to keep an artery open and prevent restenosis.

Mediastinum

Central compartment of the thoracic cavity where the heart sits.

Base of the heart

Wide, superior portion where great vessels attach.

Apex of the heart

Tapered inferior end that tilts to the left.

Quiescent period

Phase when all four chambers are in diastole, about 0.4 seconds.

Dicrotic notch

brief rise in arterial pressure when the aortic valve closes.

Systole

Contraction phase; ventricles eject blood.

Diastole

Relaxation phase; ventricles fill with blood.

S1 (first heart sound)

Lubb; closure of AV valves during ventricular contraction.

S2 (second heart sound)

Dupp; closure of semilunar valves at the start of diastole.