Electrical Conducting System of the Heart

Vocabulary flashcards covering the components, pathways, autonomous mechanisms, and EKG wave representations of the heart's electrical conducting system.

Electrical conducting system of the heart

The internal preprogrammed system of specialized tissues that coordinates the heart's contractions so the atria and ventricles do not contract randomly.

Sinoatrial (SA) node

The pacemaker of the heart located in the right atrium that receives sympathetic and parasympathetic potentials and initiates spontaneous depolarization to control cardiac contractions.

Depolarization (in muscular activity)

The electrical event in heart muscle tissue that is synonymous with contraction or the beginning of a contraction.

Atrioventricular (AV) node

A bundle of fibers that receives depolarization from the atria and delays the electrical impulse for a fraction of a second, allowing time for blood to travel into the ventricles.

Bundle fibers (Bundle branches)

Conducting pathways running down the center of the heart near the septum that carry action potentials toward the apex.

Purkinje fibers

Fibers that branch off from the bundle branches and run superiorly back up into the ventricular walls to stimulate upward contraction from the apex.

Intrinsic contraction

The heart's ability to depolarize and contract automatically without nervous system stimulation, occurring at an average rate of $80$ to $100$ beats per minute (usually $80$).

Spontaneous depolarization

The automatic depolarization of the SA node $80$ to $100$ times a minute without external stimulus, caused by leaky sodium channels.

Parasympathetic impulses

Impulses sent from the brain that tell the SA node to fire less often, slowing down the heart rate.

Sympathetic impulses

Impulses sent from the brain that tell the SA node to fire more often, speeding up the heart rate.

EKG (ECG)

Electrocardiogram; a diagnostic tool that measures voltage changes and action potential signatures traveling through the heart to evaluate its electrical conducting system.

P wave

The initial portion of an EKG wave representing atrial depolarization and the resulting contraction of the atria.

QRS complex

The large central deflection on an EKG representing ventricular depolarization and contraction, whose large signal simultaneously masks atrial repolarization.

T wave

The signature on an EKG wave representing ventricular repolarization and the beginning of the ventricular relaxation period.

Repolarization (in muscular activity)

The electrical resetting of muscle tissue that is synonymous with relaxation.