Cardiovascular System - The Heart and Circulation

A comprehensive vocabulary review of the cardiovascular system covering heart anatomy, circulation pathways, ECG waves, heart sounds, cardiac cycle phases, and blood pressure regulation.

Mediastinum

The anatomical region in between the two lungs where the heart is situated.

Sinoatrial (SA) node

The pacemaker of the heart located in the right atrium that produces cardiac impulses.

Atrioventricular (AV) node

The component situated in the right atrium that conducts cardiac impulses from the atria to the ventricles.

Tricuspid valve

The right atrioventricular valve formed by three cusps that allows communication between the right atrium and right ventricle.

Mitral (Bicuspid) valve

The left atrioventricular valve formed by two cusps that allows blood flow from the left atrium to the left ventricle.

Interatrial septum

The fibrous septum that separates the right and left atria from one another.

Interventricular septum

The septum separating the right and left ventricles, consisting of a membranous upper part and a muscular lower part.

Pericardium

The outer covering of the heart made of two layers: the outer parietal pericardium and the inner visceral pericardium.

Myocardium

The middle layer of the heart wall formed by cardiac muscle fibers (cardiac myocytes), responsible for the heart's pumping action.

Endocardium

The innermost layer of the heart wall, a thin glistening membrane formed by a single layer of endothelial cells.

Semilunar valves

Valves located at the openings of the systemic aorta and pulmonary artery, known as the aortic and pulmonary valves respectively.

Chordae tendineae

Fibrous cords that attach the cusps of atrioventricular valves to the papillary muscles.

Chronotropic action

Refers to the frequency of the heartbeat or heart rate; classified as tachycardia (increase) or bradycardia (decrease).

Inotropic action

Refers to the force of contraction of the heart; can be positive (increase) or negative (decrease).

Dromotropic action

Refers to the velocity of conduction of the impulse through the heart.

Bathmotropic action

Refers to the excitability of the cardiac muscle.

Resistance vessels

A term for arterioles because they offering peripheral resistance to blood flow.

Capacitance vessels

A term for venules because they can hold a large quantity of blood at one time.

Arteriosclerosis

A disease of the arteries associated with hardening, thickening, and loss of elasticity in the vessel walls.

Atherosclerosis

A progressive disease marked by the narrowing of the arterial lumen due to the deposition of cholesterol (atherosclerotic plaques).

Systemic circulation

Also known as greater circulation; the path of oxygenated blood from the left ventricle through the body and back to the right atrium as venous blood.

Pulmonary circulation

Also known as lesser circulation; the path of deoxygenated blood from the right ventricle to the lungs and back to the left atrium as oxygenated blood.

Coronary sinus

A large vascular sinus in the coronary sulcus where most deoxygenated blood from the myocardium drains before entering the right atrium.

Intercalated discs

Irregular transverse thickenings of the sarcolemma that connect the ends of cardiac muscle fibers.

Gap junctions

Components of intercalated discs that allow muscle action potentials to conduct from one muscle fiber to its neighbors for coordinated contraction.

Bundle of His

The atrioventricular (AV) bundle which conducts action potentials from the AV node toward the bundle branches.

Purkinje fibers

Large-diameter fibers that rapidly conduct action potentials from the heart apex upward to the ventricular myocardium.

Refractory period

The time interval during which a second contraction cannot be triggered; in cardiac muscle, it lasts longer than the contraction itself.

P wave

A small upward deflection in an ECG representing atrial depolarization as it spreads from the SA node through the atria.

QRS complex

An ECG component representing rapid ventricular depolarization.

T wave

An ECG wave indicating ventricular repolarization, which occurs more slowly than depolarization.

P-Q interval

The time required for an action potential to travel through the atria, AV node, and the remaining conduction system fibers.

End-diastolic volume (EDV)

The amount of blood remaining in each ventricle at the end of its relaxation period, approximately $130\,mL$ to $150\,mL$.

End-systolic volume (ESV)

The volume of blood remaining in each ventricle at the end of systole, approximately $60\,mL$.

Stroke volume (SV)

The volume of blood ejected per beat from each ventricle, calculated as $SV = EDV - ESV$, normally $70\,mL$ at rest.

Ejection fraction

The fraction of end-diastolic volume ejected per beat, normally $60\%$ to $65\%$.

Auscultation

The act of listening to sounds within the body, typically performed with a stethoscope.

Cardiac output (CO)

The volume of blood ejected from the left or right ventricle into the aorta or pulmonary trunk each minute.

Preload

The degree of stretch on the heart before it contracts, proportional to the end-diastolic volume.

Afterload

The pressure that must be exceeded (aortic or pulmonary pressure) before ejection of blood from the ventricles can occur.

Mean arterial pressure (MAP)

The average blood pressure in the arteries, calculated as the diastolic pressure plus one-third of the pulse pressure.

Vasomotor tone

A moderate state of tonic contraction or vasoconstriction that sets the resting level of systemic vascular resistance.

Baroreceptors

Sensory receptors in the carotid sinus and aorta wall that monitor changes in blood pressure and stretch.

Chemoreceptor reflex

A sensory mechanism that monitors chemical compositions of blood, specifically levels of $O_2$, $CO_2$, and $H^+$.

Renin-angiotensin-aldosterone (RAA) system

A hormonal system where kidneys release renin to ultimately produce angiotensin II, a potent vasoconstrictor that also stimulates aldosterone secretion.

Angina pectoris

Chest pain or discomfort resulting from myocardial ischemia where the heart muscle receives insufficient oxygenated blood.

Myocardial Infarction

Also known as a heart attack; the death of cardiac muscle due to prolonged severe ischemia.