Heart Anatomy and Electrical Activity

These flashcards cover key terms and concepts related to heart anatomy, electrical activity, and EKG interpretation.

Epicardium

The outermost layer of the heart, where coronary arteries lie.

Myocardium

The middle muscular layer of the heart responsible for contracting.

Endocardium

The innermost layer of the heart that is water-tight, lining the chambers and forming the heart valves.

Interventricular septum

A band of tissue that separates the right and left ventricles.

Interatrial septum

The wall that separates the right and left atria.

AV valves

Atrioventricular valves that open downward to prevent backflow of blood.

Semilunar valves

Valves that open upward to prevent backflow of blood from the arteries into the ventricles.

Superior Vena Cava (SVC)

A large vein that returns deoxygenated blood from the upper body to the heart.

Inferior Vena Cava (IVC)

A large vein that returns deoxygenated blood from the lower body to the heart.

Diastole

The phase of the cardiac cycle where ventricles relax and fill with blood.

Systole

The phase of the cardiac cycle where ventricles contract and expel blood.

Blood flow through the heart

The path taken by blood as it moves through the heart: SVC/IVC -> RA -> Tricuspid Valve -> RV -> Pulmonary Valve -> PA -> Lung -> Pulmonary Veins -> LA -> Mitral Valve -> LV -> Aorta -> Body.

Action Potential

What happens to a cardiac cell when stimulated by an electrical charge, consisting of several phases.

Refractory Periods

Periods where a cardiac cell resists responding to depolarization; includes absolute, relative, and supernormal periods.

Automaticity

The ability of cardiac cells to create electrical impulses.

Excitability

The ability of cardiac cells to respond to electrical impulses by depolarizing.

Sinus node

The normal pacemaker of the heart.

Escape rhythm

Occurs when a lower pacemaker takes control over the primary pacemaker, resulting in a slower heart rate.

Arrhythmia

An abnormal heart rhythm.

12-lead EKG

A printout of the heart’s electrical activity from 12 different angles.

Einthoven’s Law

Lead I + Lead III = Lead II; indicates the relationship between bipolar leads.

Electrocardiogram (EKG)

The printed record of the heart's electrical impulses.

P-wave

Represents atrial depolarization on an EKG.

QRS complex

Represents ventricular depolarization on an EKG.

T-wave

Represents ventricular repolarization on an EKG.

First Degree AV Block

A delay in impulse transmission between atria and ventricles where all impulses are transmitted.

Second Degree AV Block - Mobitz Type I (Wenckebach)

Some impulses get through to ventricles; some do not, with a gradual prolongation of PR interval.

Second Degree AV Block - Mobitz Type II

Some impulses get through to the ventricles while others do not, with constant PR intervals on conducted beats.

Third Degree AV Block

No impulses are transmitted from the atria to the ventricles; an escape pacemaker must take over.