Chapter 20 A& P 2

Heart

A four-chambered muscular organ responsible for pumping blood through the body's blood vessels.

Pericardium

The sac that encases the heart, providing structural support and protection.

Pulmonary circulation

The movement of blood from the right side of the heart to the lungs and back to the left side.

Systemic circulation

The movement of blood from the left side of the heart to the body tissues and back to the right side.

Epicardium

The outer layer of the heart wall, also known as the visceral pericardium.

Myocardium

The middle layer of the heart wall, made up of cardiac muscle responsible for contraction.

Endocardium

The smooth inner surface of the heart chambers.

Atrioventricular valve (AV valve)

Valves located between the atria and ventricles of the heart, allowing blood flow from atria to ventricles.

Semilunar valve

Valves located between the ventricles and the arteries, preventing backflow into the ventricles.

SA node (Sinoatrial node)

The natural pacemaker of the heart that initiates action potentials for heart contractions.

Action potential

An electrical impulse that triggers muscle contractions in the heart.

Cardiac output (CO)

The amount of blood pumped by the heart per minute, calculated as stroke volume multiplied by heart rate.

Preload

The initial stretching of the heart's ventricular walls, directly related to the volume of blood returning to the heart.

Afterload

The pressure that the contracting ventricles must overcome to eject blood into the aorta.

Stroke volume (SV)

The amount of blood pumped by the heart with each beat, calculated as end-diastolic volume minus end-systolic volume.

Mean Arterial Pressure (MAP)

An average arterial blood pressure during a single cardiac cycle.

Cardiac reserve

The difference between cardiac output at rest and the maximum cardiac output during activity.

Epinephrine

A hormone released from the adrenal medulla that increases heart rate and force of contraction.

Norepinephrine

A hormone that increases heart rate and contractility, released by sympathetic nerve fibers.