The Cardiovascular System: Anatomy, Conduction, Mechanics, and Regulation

Vocabulary practice flashcards covering cardiovascular anatomy, circuits, cardiac muscle histology, electrical conduction, ECG components, mechanics of the cardiac cycle, stroke volume determinants, and autonomic regulation.

Systemic Circuit

The cardiovascular circuit that carries oxygenated blood from the left ventricle into the aorta to body tissues and returns deoxygenated blood to the right atrium.

Pulmonary Circuit

The cardiovascular circuit that carries deoxygenated blood from the right ventricle into the pulmonary trunk to the lungs for oxygen reloading and returns oxygenated blood to the left atrium.

Cardiac Output

The volume of blood pumped by a ventricle per unit of time, calculated as $\text{CO} = \text{SV} \times \text{HR}$, averaging approximately $5\,L/min$ at rest and increasing up to $30\,L/min$ during maximal exercise.

Bicuspid Valve

An atrioventricular valve (also known as the mitral valve) located between the left atrium and left ventricle, consisting of two cusps.

Tricuspid Valve

An atrioventricular valve located between the right atrium and right ventricle, consisting of three cusps.

Chordae Tendinae

Tendinous cords attached to the cusps of atrioventricular valves that connect to papillary muscles, preventing valve prolapse into the atria during ventricular contraction.

Papillary Muscles

Specialized muscular projections in the ventricular walls that contract simultaneously with the ventricles to regulate tension in the chordae tendinae.

Right Coronary Artery

A major vessel originating on the ascending aorta that gives rise to the marginal and posterior interventricular branches, supplying the SA node, AV node, right atrium, interventricular septum, and both ventricles.

Left Coronary Artery

A major vessel originating on the ascending aorta that gives rise to the circumflex and anterior interventricular branches, supplying the SA node, left atrium, interventricular septum, and both ventricles.

Coronary Sinus

A large venous channel on the posterior aspect of the heart that receives blood from the great and middle cardiac veins and empties directly into the right atrium.

Intercalated Discs

Microscopic structural junctional sites between adjacent cardiac muscle fibers containing desmosomes for physical cohesion and gap junctions for electrical impulse transmission.

Gap Junctions

Small protein channels located within intercalated discs that allow electrical impulses and ions to pass rapidly from one cardiac muscle cell to the next.

Sinoatrial (SA) Node

The natural pacemaker of the heart located in the right atrial wall, which spontaneously discharges action potentials at an intrinsic rate of $100\text{--}120\,bpm$, modified to ~$70\,bpm$ at rest by autonomic nerves.

Atrioventricular (AV) Node

A node of poorly conducting tissue at the AV border that delays the cardiac electrical impulse by approximately $0.1\,s$, giving the atria time to fully empty before the ventricles contract.

Purkinje Fibers

Specialized conduction fibers in the subendocardial conducting network that distribute electrical excitation rapidly throughout the ventricular myocardium.

Absolute Refractory Period

The duration during an action potential (lasting about $250\,ms$ in heart muscle) when a cell will not respond to any electrical stimulus regardless of strength.

Pacemaker Potential

An unstable resting membrane potential in autorhythmic cardiac fibers characterized by slow spontaneous depolarization driven by slow inward $\text{Na}^+$ flux.

P Wave

The initial wave of an electrocardiogram (ECG) trace representing atrial depolarization.

QRS Complex

The ECG wave deflection representing ventricular depolarization while masking simultaneous atrial repolarization.

T Wave

The component of an ECG trace representing ventricular repolarization.

Ventricular Systole

The period of ventricular muscle contraction initiated by depolarization, causing a rise in intraventricular pressure, rapid closure of AV valves, and ejection of blood into the major arteries.

Ventricular Diastole

The period of ventricular relaxation initiated by muscle repolarization, leading to a drop in intraventricular pressure, rapid closure of semilunar valves, and passive filling of the ventricles.

Preload

The end-diastolic volume or degree of stretch on cardiac muscle fibers prior to contraction, which directly influences stroke volume.

Afterload

The pressure in the aorta or pulmonary trunk that ventricles must overcome in order to open the semilunar valves and eject blood.

Frank-Starling Mechanism

The intrinsic property of cardiac muscle where an increase in preload stretches cardiac sarcomeres closer to an optimal resting length ($2.2\,\mu m$), systematically increasing stroke volume.

Active Contractility

An increase in the force of cardiac muscle contraction driven by sympathetic nerve stimulation and norepinephrine release via cyclic AMP second-messenger pathways.

Chronotropic Effects

Mechanisms or factors that modify heart rate by changing the frequency of action potential discharge in pacemaker cells.

Cardioacceleratory Center

A region in the medulla oblongata that projects sympathetic neurons to the SA node, AV node, and myocardium to increase heart rate and force of contraction.

Cardioinhibitory Center

A region in the medulla oblongata that projects parasympathetic signals via the vagus nerve (CN X) to the SA and AV nodes to decrease heart rate.

Hyperkalemia

An excess concentration of ionic potassium in the blood that leads to heart block and cardiac arrest.

Hypercalcemia

An excess concentration of ionic calcium in the blood that dramatically increases heart irritability and leads to spastic contractions.