Angina pectoris: Severe suffocating chest pain, caused by a brief lack of oxygen supply to the heart muscle.
Arteries: Vessels that carry blood away from the heart; they are oxygenated, except for arteries in the pulmonary circulation and umbilical cord of a fetus.
Atria: The two superior receiving chambers of the heart with walls ridged by pectinate muscles, and contain anterior ear-shaped pouches called auricles which increase the atrial volume; their function is to pass blood to the ventricles; the right atrium receives blood from the coronary sinus, superior and inferior vena cava; the left atrium receives blood from the right and left pulmonary veins; they are separated by the interatrial septum.
Atrioventricular valves: The two valves that prevent backflow into the atria when the ventricles are contracting; they are pliable and remain open most of the time; the cusps of the valves are attached to chordae tendineae which are attached to papillary muscles in the ventricles; they include the tricuspid valve between the right atrium and right ventricle of the heart, which consists of three fibrous cusps (also called right AV valve), and the bicuspid valve between the left atrium and left ventricle of the heart, which consists of two fibrous cusps (also called mitral valve, or left AV valve).
Blood circulation: The course of the blood from the heart through the arteries, capillaries, veins, and back to the heart, which is subdivided into three pathways. (1) the pulmonary circulation, in which deoxygenated blood flows from the right ventricle through the pulmonary arteries to the capillaries of the lungs, and oxygenated blood returns through the pulmonary veins to the left atrium. (2) the systemic circulation, in which oxygenated blood flows from the left ventricle to the aorta and through the arteries to the capillaries of the body, and deoxygenated blood returns through the veins and the superior and inferior vena cava to the right atrium. (3) the coronary circulation that supplies the myocardium, in which blood flows from the ascending aorta, through the coronary arteries and capillaries, and returns through the cardiac veins and coronary sinus to the right atrium.
Bradycardia: An abnormally slow, resting heartbeat or pulse rate, that is under 50 beats per minute.
Cardiac arrest: Complete cessation of cardiac activity.
Cardiac centers: Nuclei of the reticular formation in the medulla oblongata that regulate the heart; the cardioacceleratory center innervates the SA and AV nodes, myocardium and coronary arteries through the sympathetic division of the ANS; the cardioinhibitory center sends inhibitory nerve impulses to the SA and AV nodes through the parasympathetic division of the ANS.
Cardiac conduction system: The system of specialized myocardial conducting cells that transmit electrical impulses to the heart muscle; the impulses are initiated at the sinoatrial (SA) node (pacemaker) which innervate the atria, then the impulses are conducted to the atrioventricular (AV) node, the atrioventricular (AV) bundle (bundle of His), the right and left bundle branches, and the Purkinje fibers (subendocardial conducting network) which innervate the ventricles. Also called the intrinsic conducting system of the heart.
Cardiac contractility: A measure of cardiac pump performance; the degree to which cardiac muscle fibers can contract and develop increased tension when activated by a stimulus.
Cardiac cycle: The complete heartbeat consisting of systole (contraction) and diastole (relaxation) of both atria and both ventricles, with the intervals in between.
Cardiac output (CO): Amount of blood pumped out of each ventricle in one minute, in L / min; CO is equal to stroke volume (SV) times heart rate (HR), according to the formula: CO = SV ∙ HR.
Cardiac reserve: The difference between the resting cardiac output (about 5 L/min and the maximal cardiac output (between 15 - 35 L/min), which depends on the physical condition of the person.
Cerebrovascular accident (CVA): Destruction of brain tissue (infarction) resulting from impairment of cerebral circulation. CVA is the third most common cause of death in the U.S.A. Also called a cerebral stroke.
Coronary arteries: First small branches off the ascending aorta that supply the myocardium of the heart.
Coronary artery disease: A condition such as atherosclerosis, that causes narrowing of coronary arteries so that blood flow to the heart is reduced; the result is coronary heart disease (CHD), in which the heart muscle receives inadequate blood flow due to an interruption of its blood supply.
Coronary sinus and cardiac veins: Drains blood from the coronary circulation and returns it to the right atrium.
Coronary sulcus: A groove on the outer surface of the heart that encircles the junction of the atria and ventricles. Also called the atrioventricular groove, or AV groove.
Diastole: In the cardiac cycle, the phase of relaxation or dilation of the ventricles.
Diastolic blood pressure (DBP): The force exerted by blood on arterial walls during ventricular relaxation; the lowest blood pressure measured in the large arteries, normally about 80 mm Hg (torr) in a young adult.
Ductus arteriosus: Fetal heart structure; a fetal vessel connecting the pulmonary trunk to the aortic arch, which acts like a shunt to allow fetal blood to bypass the lungs; it closes after birth, and the fibrous remnants are called the ligamentum arteriosum.
Electrocardiogram: Graphic record of the heart's electrical activity, displayed as voltage changes over time; the initial deflection of the cardiac cycle is the P wave that represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization. Also called ECG or EKG.
Fibrillation: Rapid contractions or twitching of muscular fibrils. Atrial fibrillation is the rapid irregular twitchings of atrial muscle that results in the cessation of atrial pumping. Ventricular fibrillation is the rapid irregular twitchings of ventricular muscle that causes heart failure and death, unless reversed by defibrillation.
Fibrous skeleton of heart: A complex framework of fibrous tissue that anchors cardiac muscle fibers, supports the heart valves and openings to the great vessels, and acts as an electrical insulator to limit the spread of action potentials to specific paths.
Foramen ovale: Fetal heart structure; an opening in the interatrial septum that allows blood entering the right atrium to flow directly into the left atrium; closes after birth and remnants are seen as an oval depression on the lower part of the septum of the right atrium, which is called the fossa ovalis.
Frank-Starling law of the heart: The greater the volume of blood in the heart during diastole, the greater the force of contraction during systole.
Heart block: Impaired transmission of electrical impulses from atria to ventricles, resulting in dysrhythmia. In first-degree heart block, there is prolongation of AV conduction time (PR interval). In second-degree heart block, some atrial impulses fail to reach the ventricles, thus some ventricular beats are missing. In third degree heart block, complete atrioventricular dissociation occurs, thus atria and ventricles beat independently.
Heart murmur: Abnormal heart sound; usually resulting from valve problems.
Heart rate (HR): The number of beats per minute (bpm) for the heart.
Heart wall and coverings: The heart wall consists of three layers: the endocardium is the endothelial membrane that lines the interior of the heart chambers and is continuous with the endothelial lining of the blood vessels; the myocardium is the middle layer composed of cardiac muscle tissue and constitutes the bulk of the heart; the epicardium is the visceral layer of the serous pericardium that covers the external surface of the heart; the parietal layer of the serous pericardium lines the internal surface of the fibrous pericardium, which is the superficial layer of the heart that protects, anchors, and prevents overfilling
Interventricular sulcus: A groove on the surface of the heart, marking the location of the septum between the two ventricles. Also called interventricular groove, or IV groove.
Myocardial infarction (MI): Prolonged blockage of coronary blood flow that causes necrosis of myocardial tissue. MI is the most common cause of death in the U.S.A. Also called a heart attack.
Semilunar valves: The two valves that prevent blood return back to the ventricles after systole (contraction); they are rigid and remain closed most of the time, and consist of three fibrous semilunar cusps; they include the aortic valve between the left ventricle and the ascending aorta (also called left SL valve), and the pulmonary valve between the right ventricle and the pulmonary trunk (also called right SL valve).
Stroke volume (SV): Amount of blood pumped out of a ventricle during one contraction; SV is equal to end diastolic volume (EDV) minus end systolic volume (ESV), according to the formula: SV = EDV ─ ESV.
Systole: In the cardiac cycle, the phase of contraction of the ventricles.
Systolic blood pressure (SBP): The force exerted by blood on arterial walls during ventricular contraction; the highest blood pressure measured in the large arteries, normally about 120 mm Hg (torr) in a young adult.
Tachycardia: An abnormally rapid, resting heartbeat or pulse rate, that is over 100 beats per minute.
Vascular anastomoses: Connecting channels that allow blood to be supplied to arteries, or drained from veins, even if one channel is blocked; many are found in the brain and heart.
Veins: Vessels that carry blood toward the heart; they are formed where venules converge, and have thin walls, large lumens, and valves to prevent backflow of blood; they are capacitance vessels that act as blood reservoirs and contain up to 60% of the blood supply.
Venous sinuses: Flattened veins with thin walls; found in heart (coronary sinus) and brain (dural sinuses).
Ventricles: The two inferior discharging chambers of the heart that are separated internally by the interventricular septum; their walls are ridged by trabeculae carneae, and papillary muscles project into the ventricular cavities; they function as the major blood pumps; the right ventricle pumps blood into the pulmonary trunk; the left ventricle pumps blood into the aorta.
Ventricular afterload: The back pressure exerted by the aorta and pulmonary trunk that the ventricles must overcome to eject blood.
Ventricular preload: The degree of stretch of muscles in the ventricles prior to contraction.