Heart Anatomy and Physiology

Comprehensive vocabulary flashcards covering the anatomical structures, circuits, electrical conduction pathway, cardiac cycle phases, volumes, and regulatory mechanisms of the human heart.

Pericardium

The double-walled sac enclosing the heart, consisting of a superficial fibrous pericardium and a deep two-layered serous pericardium (parietal layer and visceral layer) separated by the pericardial cavity.

Pericardial Cavity

A fluid-filled space between the parietal and visceral layers of the serous pericardium that decreases friction during heartbeats.

Auricles

Small, wrinkled, ear-shaped appendages protruding from the atria that function to increase atrial volume.

Pectinate Muscles

Parallel muscular ridges located along the internal walls of the atria.

Trabeculae Carneae

Irregular muscular ridges that crisscross the internal surfaces of the ventricular walls.

Papillary Muscles

Cone-like muscular projections in the ventricular cavities that anchor the chordae tendineae to prevent valve cusp eversion.

Pulmonary Circuit

The low-pressure, short blood pathway pumped by the right side of the heart that transports oxygen-poor blood to the lungs for gas exchange and returns oxygen-rich blood to the heart.

Systemic Circuit

The long, high-resistance pathway pumped by the left side of the heart that delivers oxygenated blood to all body tissues and returns deoxygenated blood to the heart.

Interventricular Septum

The thick internal muscular wall that divides the right and left ventricles, whose thickness reflects the higher pressures generated by the left ventricle compared to the right.

Coronary Circulation

The functional blood supply of the heart wall itself, which branches from the base of the aorta via the right and left coronary arteries and empties into the right atrium via cardiac veins and the coronary sinus.

Atrioventricular (AV) Valves

Valves positioned between the atria and ventricles (the tricuspid valve on the right and the mitral valve on the left) that prevent backflow into the atria when the ventricles contract.

Chordae Tendineae

Collagenous cords referred to as 'heart strings' that anchor the cusps of the atrioventricular valves to papillary muscles in the ventricular walls.

Semilunar (SL) Valves

The aortic and pulmonary valves each made of three pocket-like cusps that prevent arterial blood backflow into the ventricles during ventricular relaxation (diastole).

Intercalated Discs

Specialized junctional complexes between adjacent cardiac muscle cells containing desmosomes that prevent separation during contraction and gap junctions that allow direct ion passage.

Functional Syncytium

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

Automaticity

The intrinsic ability of approximately $1\%$ of specialized cardiac muscle cells to initiate their own action potentials spontaneously and rhythmically without nervous stimulation.

Plateau Phase

A prolonged depolarization phase in cardiac contractile cells lasting approximately $175\text{ msec}$, caused by an influx of $\text{Ca}^{2+}$ through slow calcium channels that balances potassium efflux.

Sinoatrial (SA) Node

The primary intrinsic pacemaker of the heart located in the right atrium that spontaneously depolarizes to initiate impulses setting the heart's normal sinus rhythm.

Atrioventricular (AV) Node

A cluster of specialized conduction cells located near the interatrial septum that delays the electrical impulse before transmitting it to the atrioventricular bundle.

Purkinje Fibers

The terminal conducting fibers that branch through the interventricular septum and into the ventricular walls to stimulate synchronous ventricular contraction.

P Wave

The first deflection wave on an electrocardiogram (ECG) representing atrial depolarization initiated by the SA node.

QRS Complex

The large spike deflection on an ECG produced by ventricular depolarization, preceding ventricular contraction.

T Wave

The deflection wave on an ECG that represents ventricular repolarization occurring prior to ventricular relaxation.

Junctional Rhythm

An abnormal cardiac rhythm occurring when the SA node is nonfunctional, characterized by absent P waves and paced by the AV node at $40\text{--}60\text{ beats/min}$.

Ventricular Fibrillation

A chaotic, grossly irregular ECG deflection pattern marked by rapid and uncoordinated ventricular contractions, typically seen during acute heart attacks or electrical shock.

Systole

The contraction period of a heart chamber during the cardiac cycle that drives blood forward.

Diastole

The relaxation period of a heart chamber during the cardiac cycle when the chamber fills with blood.

Isovolumetric Contraction Phase

The split-second period during ventricular systole when the ventricles are contracting, all four valves are completely closed, and ventricular blood volume remains unchanged.

Cardiac Output (CO)

The total volume of blood pumped by each ventricle in one minute, calculated as the product of heart rate and stroke volume ($\text{CO} = \text{HR} \times \text{SV}$).

Stroke Volume (SV)

The volume of blood ejected by a single ventricle with each heartbeat, calculated as the difference between end diastolic volume and end systolic volume ($\text{SV} = \text{EDV} - \text{ESV}$).

End Diastolic Volume (EDV)

The volume of blood collected in a ventricle at the end of diastole, just before contraction begins.

End Systolic Volume (ESV)

The volume of blood remaining in a ventricle at the end of systole, after contraction is complete.

Cardiac Reserve

The difference between an individual's resting cardiac output and their maximum cardiac output.

Preload

The degree of stretch experienced by cardiac muscle fibers immediately prior to contraction, governed by the Frank-Starling law of the heart.

Frank-Starling Law of the Heart

The physiological relationship stating that within physiological limits, greater stretch of ventricular myocardium caused by increased venous return produces greater contractile force and increased stroke volume.

Contractility

The intrinsic contractile strength of cardiac muscle at a given muscle fiber length, independent of muscle stretch and end diastolic volume.

Afterload

The back pressure exerted by arterial blood that the ventricles must overcome to open the semilunar valves and eject blood.

Cardioacceleratory Center

A cluster of neurons located in the medulla oblongata that projects via sympathetic fibers to increase heart rate and force of contraction.

Cardioinhibitory Center

A regulatory center located in the medulla oblongata that projects parasympathetic signals via the vagus nerve to slow heart rate.

Vagal Tone

The continuous inhibitory resting influence exerted by parasympathetic fibers of the vagus nerve that maintains resting heart rate lower than the SA node's intrinsic rate.

Tachycardia

An abnormally rapid resting heart rate exceeding $100\text{ bpm}$ that, if persistent, can lead to fibrillation.

Bradycardia

A slow resting heart rate below $60\text{ bpm}$, which can indicate inadequate circulation or be a healthy adaptation in endurance athletes.

Atherosclerosis

A vascular disease characterized by the buildup of fatty deposits inside arterial walls, narrowing the lumen and potentially causing coronary artery blockage and myocardial infarction.

Foramen Ovale

A fetal vascular shunt in the interatrial septum allowing blood to bypass the nonfunctional pulmonary circuit by traveling directly from the right atrium to the left atrium.

Fossa Ovalis

A shallow depression in the adult interatrial septum that marks the site of the closed fetal foramen ovale.

Ductus Arteriosus

A fetal vascular shunt connecting the pulmonary trunk directly to the aorta, diverting most blood away from the immature lungs.

Ligamentum Arteriosum

The fibrous ligamentous remnant in the adult heart connecting the pulmonary trunk to the aortic arch, formed by the closure of the fetal ductus arteriosus.