Cardiac Anatomy and Physiology Vocabulary Flashcards

Vocabulary flashcards covering key terms in cardiac anatomy, histology, electrophysiology, excitation-contraction coupling, cardiac signaling, and physical exam findings from the lecture notes.

Pericardium

A fibroserous sac enclosing the heart and roots of the great vessels, composed of visceral and parietal layers filled with pericardial fluid to allow minimal-friction beating.

Intercalated Discs

Microscopic identifying features of cardiac muscle (also called lines of Eberth) occurring at the Z line that connect individual myocardial cells into a functional syncytium.

Desmosomes

Cell junction structures within intercalated discs that anchor the cell membrane to the intermediate filament network, preventing cell separation during contraction.

Fascia Adherens

Anchoring sites for actin within intercalated discs that connect to the closest sarcomere.

Gap Junctions

Junctions within intercalated discs that connect the cytoplasms of neighboring cells electrically, allowing passage of ions and propagation of action potentials.

Area Composita

The single functional unit formed by the combination of desmosomes, fascia adherens junctions, and gap junctions within the intercalated disc.

Titin

A large cardiac protein (also called connectin) that tethers myosin to the Z line of the sarcomere and provides elasticity.

T Tubules

Invaginations of the sarcolemma oriented at right angles at terminal cisternae sacs that increase cell surface area for ion transport and electrical transmission.

Sinoatrial (SA) Node

The natural pacemaker of the heart located at the junction of the right atrium and superior vena cava at the crista terminalis, with an intrinsic rate of $60\text{--}100\text{ bpm}$.

Atrioventricular (AV) Node

Conduction structure that delays electrical impulses to allow atrial contraction prior to ventricular contraction, with an intrinsic rate of $45\text{--}50\text{ bpm}$.

Purkinje Fibers

Specialized, rapidly conducting ventricular cardiac fibers with an intrinsic firing rate of $15\text{--}40\text{ bpm}$.

Fast Response Action Potential

Electrical response in normal atrial, ventricular, and Purkinje cells characterized by rapid depolarization via fast voltage-dependent $Na^+$ channels and a sustained plateau.

Slow Response Action Potential

Electrical response occurring in SA and AV nodes characterized by spontaneous phase 4 depolarization driven by inward calcium current ($I_{\text{Ca,L}}$).

Absolute Refractory Period

The period during phases 0, 1, 2, and part of 3 of the action potential during which a second action potential cannot be initiated by any stimulus.

Relative Refractory Period

The period during phase 3 after reaching threshold potential during which an action potential can be triggered, but requires a larger than normal stimulus.

Supernormal Excitatory Period

A vulnerable zone extending from the end of phase 3 to the beginning of phase 4 where a small stimulus can trigger an action potential and precipitate dysrhythmias.

Troponin T (TnT)

The subunit of the troponin complex that links the complex to the actin and tropomyosin molecules.

Troponin I (TnI)

The subunit of the troponin complex that inhibits the ATPase activity of the actin-myosin interaction, measured in clinical heart tests.

Troponin C (TnC)

The subunit of the troponin complex responsible for binding calcium ions to regulate the contractile process.

Phospholamban

A major regulator of the SERCA pump that inhibits $Ca^{2+}$ uptake into the sarcoplasmic reticulum in its dephosphorylated state.

Bezold-Jarisch Reflex

A cardiac reflex characterized by increased vagal tone secondary to myocardial ischemia, commonly seen in inferior STEMI.

First Heart Sound (S1)

A high-pitched sound heard best at the apex, caused by the closure of the mitral and tricuspid valves at the beginning of systole.

Second Heart Sound (S2)

A high-pitched sound heard best at the base, caused by the closure of the aortic ($A_2$) and pulmonic ($P_2$) valves at the end of systole.

S3 Heart Sound

A low-pitched diastolic ventricular gallop sound ("Lub de BOOM") during rapid ventricular filling, indicating heart failure or volume overload in adults.

S4 Heart Sound

A low-pitched diastolic atrial gallop sound ("Bulubdub") caused by atrial contraction into a stiff left ventricle.

Pericardial Knock

An extra diastolic sound resulting from the abrupt cessation of ventricular filling when the expanding ventricle hits a rigid pericardium in constrictive pericarditis.

Jugular Venous a Wave

A transient jugular venous distension caused by back pressure from right atrial contraction.

Jugular Venous v Wave

A jugular venous pressure elevation resulting from passive filling of the right atrium during systole while the tricuspid valve is closed.

Jugular Venous y Descent

A drop in right atrial pressure following the opening of the tricuspid valve in early diastole as blood rapidly empties into the right ventricle.

Cardiac Murmur

A sound generated by turbulent blood flow caused by flow across obstructions, high-output states, dilated chambers, regurgitant valves, or abnormal shunts.