The Heart 1

Diastole

Blood filling the heart, which occurs during relaxation.

Systole

Blood leaving the heart, which occurs during contraction.

Pulmonary valve

Semilunar valve located on the right side of the heart that prevents backflow into the right ventricle during diastole.

Aortic valve

Semilunar valve located on the left side of the heart that prevents backflow into the left ventricle during diastole.

AV valves

Atrioventricular valves that separate atria from ventricles; they prevent backflow into atria during contraction.

SA Node

Sinoatrial node, a group of specialized cardiac muscle cells that acts as the heart's natural pacemaker.

AV Node

Atrioventricular node that slows down electrical impulses from the SA node; acts as a backup pacemaker.

S1 (Lub)

The sound produced by the closing of AV valves at the start of systole.

S2 (Dub)

The sound produced by the closing of semilunar valves at the start of diastole.

Pacemaker system

The system that controls the heart rhythm, including the SA node, AV node, Bundle of His, and Purkinje fibers.

Action Potential in Cardiac Muscle

The rapid depolarization and repolarization of cardiac muscle cells, crucial for heart contraction.

Plateau phase

A phase in cardiac action potentials characterized by prolonged depolarization due to Ca2+ influx.

ECG (Electrocardiogram)

A test that records the electrical activity of the heart to identify irregularities in heart function.

P wave

The wave in the ECG representing atrial depolarization.

QRS complex

The segment in the ECG indicating ventricular depolarization.

T wave

The wave in the ECG showing ventricular repolarization.

QT interval

The period in the ECG covering ventricular contraction and subsequent relaxation.

Murmurs

Abnormal heart sounds caused by turbulent blood flow or backflow, indicating possible heart problems.