Chapter 15

Frank-Starling Law

The principle that the contractile force of a muscle fiber increases with an increase in muscle fiber length, to a certain extent.

Cardiac Cycle

The mechanical and electrical events that occur during one heartbeat, including phases like atrial systole and ventricular ejection.

Parasympathetic Stimulation

Division of the autonomic nervous system that decreases heart rate and cardiac output.

Sympathetic Stimulation

Division of the autonomic nervous system that increases heart rate, cardiac output, and vasoconstriction.

Isovolumetric Ventricular Contraction

A phase of the cardiac cycle where the ventricles contract with no change in volume due to closed AV valves.

P Wave

Represents atrial depolarization and contraction in an EKG.

QRS Complex

Represents ventricular depolarization and contraction in an EKG.

T Wave

Represents ventricular repolarization and relaxation in an EKG.

SA Node

Sinoatrial node, the pacemaker of the heart that initiates the heartbeat.

Capillaries

Small blood vessels where gas and nutrient exchange occurs.

Tunica Intima

The inner layer of a blood vessel, providing a smooth surface.

Tunica Media

The middle layer of a blood vessel, composed of smooth muscle that controls vasoconstriction and dilation.

Tunica Externa

The outer layer of a blood vessel, made of connective tissue.

Atria

The upper chambers of the heart that receive blood.

Ventricles

The lower chambers of the heart that pump blood out.

Tricuspid Valve

Right atrioventricular valve between the right atrium and right ventricle.

Mitral Valve

Left atrioventricular valve between the left atrium and left ventricle.

Pulmonary Valve

Semilunar valve between the right ventricle and pulmonary trunk.

Aortic Valve

Semilunar valve between the left ventricle and aorta.