Cardiac Electrophysiology and Cardiac Cycle

Vocabulary flashcards covering the intrinsic conduction system of the heart, action potentials of SA nodal cells and ventricular myocytes, ECG waves, and phases of the cardiac cycle.

Sinoatrial Node (SA Node)

The pacemaker located in the right atrium that depolarizes fastest among the intrinsic conduction network and sets the speed of the heart's electrical activity.

Atrioventricular Node (AV Node)

A node located at the junction between the atria and ventricles on the right side of the heart that receives electrical signals from the SA node and introduces a slight time delay.

Bundle of His

A conducting tract that receives the electrical signal from the AV node and carries it into the septum separating the ventricles.

Bundle Branches

Conducting structures extending down the ventricular septum that carry the electrical signal to the apex of the heart.

Purkinje Fibers

Conducting fibers running along the inside of the myocardial wall that distribute the electrical signal directly to ventricular contracting myocytes.

Ventricular Contracting Myocytes

The muscle cells of the ventricles that receive signals from Purkinje fibers and perform the mechanical contraction of the heart.

Pacemaker Potential

Phase 1 of the SA nodal cell action potential characterized by gradual depolarization up to $-40\,\text{mV}$ driven by sodium influx.

iFunny Channels

Voltage-gated sodium channels in SA nodal cells that open in response to repolarization, initiating the pacemaker potential.

SA Nodal Depolarization Phase

Phase 2 of the SA nodal cell action potential occurring when voltage-gated calcium channels open at $-40\,\text{mV}$, allowing calcium influx to bring membrane potential to nearly $10\,\text{mV}$.

SA Nodal Repolarization Phase

Phase 3 of the SA nodal action potential where voltage-gated calcium channels close and voltage-gated potassium channels open, allowing potassium efflux down to $-60\,\text{mV}$.

Plateau Phase

Phase 2 of the ventricular contracting myocyte action potential where membrane potential levels off due to simultaneous calcium influx and potassium efflux.

P Wave

The deflection on an ECG representing the electrical depolarization of both atria preceding atrial contraction.

QRS Complex

The deflection on an ECG representing ventricular depolarization, which masks simultaneous atrial repolarization.

T Wave

The deflection on an ECG representing ventricular repolarization as all ventricular cells return to rest.

Mid to Late Ventricular Diastole

A period of ventricular relaxation in the cardiac cycle that consists of two subphases: ventricular filling and atrial contraction.

Ventricular Systole

The contraction period of the cardiac cycle consisting of two phases: isovolumetric contraction and ejection.

Early Ventricular Diastole

The initial period of ventricular relaxation following contraction, which includes isovolumetric relaxation.