4. Regulation of Heart Rate and Blood Flow

Heart Rate

The number of times the heart normally beats per minute in an adult.

Systemic Circulation

The process of pumping blood from the heart into the systemic circulation.

Resistance to Blood Flow

The force that opposes the movement of blood as it travels through blood vessels.

Arterial Pressure

The pressure that increases as resistance to blood flow develops.

Blood Pressure

The pressure of blood against the walls of the arteries.

Peripheral Resistance and Cardiac Output

The two main factors that determine arterial blood pressure.

Cardiac Output

The volume of blood expelled from the heart in one minute.

Heart Rate × Stroke Volume

The formula used to calculate cardiac output.

Average Cardiac Output (4–8 L/min)

The average amount of blood pumped by the heart in one minute.

Stroke Volume

The amount of blood ejected from the left ventricle with each heartbeat.

Stroke Volume (70 mL/beat)

The approximate amount of blood ejected by the left ventricle with each heartbeat.

Preload, Contractility, and Afterload

The three factors that determine stroke volume.

Preload

The force of blood flow that stretches the ventricle at the end of diastole.

Increased Preload Increases Stroke Volume

The effect of increased preload on stroke volume.

Decreased Preload Decreases Stroke Volume

The effect of decreased preload on stroke volume.

Contractility

The force of ventricular contraction.

Afterload

The resistance to ventricular ejection of blood caused by opposing pressures in the aorta and systemic circulation.

Increased Afterload Decreases Stroke Volume

The effect of increased afterload on stroke volume.

Decreased Afterload Increases Stroke Volume

The effect of decreased afterload on stroke volume.

Cardiovascular Drugs

Drugs that can increase or decrease preload and afterload, affecting stroke volume and cardiac output.

Vasodilators

Drugs that widen blood vessels and usually decrease preload and afterload.

Decrease Arterial Pressure and Cardiac Output

The effect of most vasodilators on arterial pressure and cardiac output.

Cardiac Glycosides, Antianginals, and Antidysrhythmics

The three groups of drugs discussed in the chapter that regulate heart contraction, heart rate, rhythm, and blood flow to the myocardium.

Myocardium

The muscle of the heart.

Cardiac Output

The volume of blood pumped by the heart in one minute, calculated by multiplying heart rate by stroke volume.

Peripheral Resistance

The resistance in the blood vessels that affects blood pressure and the amount of blood the heart pumps.