Chapter 18: The Cardiovascular System - The Heart

Vocabulary flashcards covering heart anatomy, circulation circuits, the conduction system, cardiac cycle, and homeostatic imbalances from Chapter 18.

Pulmonary circuit

The arteries and veins that carry blood to and from the lungs.

Systemic circuit

The blood vessels that carry blood to and from body tissues.

Mediastinum

The location of the heart between the second rib and the fifth intercostal space, on the superior surface of the diaphragm.

Apex

The pointed end of the heart that points toward the left hip; its apical impulse can be palpated between the fifth and sixth ribs.

Pericardium

A double-walled sac that surrounds the heart, consisting of a superficial fibrous layer and a deep two-layered serous layer.

Pericarditis

Inflammation of the pericardium that roughens membrane surfaces and may cause a creaking sound called a pericardial friction rub.

Cardiac tamponade

A condition where excess inflammatory fluid leaks into the pericardial space and compresses the heart, limiting its pumping ability.

Epicardium

The visceral layer of the serous pericardium that forms the external surface of the heart wall.

Myocardium

The bulk of the heart wall, consisting mostly of circular or spiral bundles of contractile cardiac muscle cells.

Cardiac skeleton

A non-excitable network of dense collagen and elastic fibers that anchors muscle fibers, supports valves, and limits the spread of action potentials.

Endocardium

The innermost layer of the heart wall that is continuous with the endothelial lining of blood vessels and lines the heart chambers.

Fossa ovalis

The remnant of the foramen ovale of the fetal heart, located in the interatrial septum.

Auricles

Appendages on the atria that function to increase atrial volume.

Coronary sinus

A systemic vein that returns blood draining from the myocardium into the right atrium.

Trabeculae carneae

Irregular ridges of muscle that mark the internal walls of the ventricles.

Chordae tendineae

Structures that anchor the atrioventricular valve cusps to the papillary muscles.

Atrioventricular (AV) valves

The two valves (tricuspid and mitral) located between the atria and ventricles that prevent backflow into the atria when ventricles contract.

Mitral valve

The left atrioventricular valve, also called the bicuspid valve, made up of two cusps.

Semilunar (SL) valves

The valves (pulmonary and aortic) located between the ventricles and major arteries that prevent backflow from the arteries into the ventricles.

Valvular stenosis

A condition where stiff valve flaps constrict the opening, forcing the heart to work harder to pump blood.

Coronary circulation

The functional blood supply of the heart itself, representing the shortest circulation in the body.

Angina pectoris

Thoracic pain caused by a temporary deficiency in blood delivery to the myocardium, weakening the cells.

Myocardial infarction (MI)

Commonly known as a heart attack; a prolonged coronary blockage that causes myocardial cell death, which is replaced by noncontractile scar tissue.

Intercalated discs

Interlocking junctions between cardiac myocytes containing desmosomes to hold cells together and gap junctions to allow for electrical coupling.

Functional syncytium

The behavior of the myocardium as a single coordinated unit due to electrical coupling via gap junctions.

Automaticity

Also called autorhythmicity; the property of cardiac pacemaker cells to spontaneously depolarize and initiate the depolarization of the entire heart.

Intrinsic cardiac conduction system

A network of noncontractile cells that initiates and distributes impulses to coordinate the heart's depolarization and contraction.

Sinoatrial (SA) node

Known as the heart's pacemaker, located in the right atrial wall; it sets the sinus rhythm at approximately $75$ beats/min.

Atrioventricular (AV) node

Located in the inferior interatrial septum; it delays impulses by about $0.1$ second to allow atria to contract before the ventricles.

Fibrillation

Rapid, irregular, and uncoordinated twitching heart contractions that cause circulation to cease and can result in brain death.

Ectopic focus

An abnormal pacemaker that may appear if the SA node is defective.

Cardioacceleratory center

A center in the medulla oblongata that sends sympathetic signals to increase both heart rate and the force of contraction.

Electrocardiogram (ECG)

A graphic recording of the heart's electrical activity, representing a composite of all action potentials at a given time.

P wave

The ECG wave corresponding to the depolarization of the SA node and the atria.

QRS complex

The ECG feature that represents ventricular depolarization and atrial repolarization.

T wave

The ECG wave corresponding to ventricular repolarization.

Systole

The period of myocardial contraction.

Diastole

The period of myocardial relaxation.

End diastolic volume (EDV)

The volume of blood in each ventricle at the end of ventricular diastole.

End systolic volume (ESV)

The volume of blood remaining in each ventricle after contraction (systole) ends.

Dicrotic notch

A brief rise in aortic pressure caused by the closure of the aortic semilunar valve as blood backflow rebounds off the valve cusps.

Cardiac output (CO)

The amount of blood pumped by each ventricle in $1$ minute; the product of heart rate ($HR$) and stroke volume ($SV$).

Cardiac reserve

The difference between resting and maximal cardiac output.

Preload

The degree to which cardiac muscle cells are stretched just before they contract.

Positive inotropic agents

Substances that increase contractility, such as epinephrine, thyroxine, and high extracellular $Ca^{2+}$.

Afterload

The back pressure exerted by arterial blood that the ventricles must overcome to eject blood.

Tachycardia

An abnormally fast heart rate, defined as more than $100$ beats/min.

Bradycardia

A resting heart rate slower than $60$ beats/min.

Congestive heart failure (CHF)

A progressive condition where cardiac output is so low that blood circulation is inadequate to meet tissue needs.

Foramen ovale

A fetal heart structure that connects the two atria, bypassing pulmonary circulation, and closes at birth.