By studying this chapter, you should be able to do the following:
Provide an overview of the design and function of the circulatory system.
Describe the cardiac cycle and the associated electrical activity recorded via the electrocardiogram.
Discuss the pattern of redistribution of blood flow during exercise.
Outline the circulatory responses to various types of exercise.
Identify the factors that regulate local blood flow during exercise.
List and discuss those factors responsible for regulation of stroke volume during exercise.
Discuss the regulation of cardiac output during exercise.
Organization of the Circulatory System
Heart: Myocardium and Cardiac Cycle
Physical Characteristics of Blood
Relationships among Pressure, Resistance, and Flow
Sources of Vascular Resistance
Changes in Oxygen Delivery to Muscle during Exercise
Changes in Cardiac Output during Exercise
Changes in Arterial-Mixed Venous O2 Content during Exercise
Redistribution of Blood Flow during Exercise
Regulation of Local Blood Flow during Exercise
Circulatory Responses to Exercise
Regulation of Cardiovascular Adjustments to Exercise
atrioventricular node (AV node)
cardiac accelerator nerves
cardiovascular control center
diastolic blood pressure
electrocardiogram (ECG or EKG)
heart rate variability
mixed venous blood
sinoatrial node (SA node)
systolic blood pressure
One of the major challenges to homeostasis posed by exercise is the increased muscular demand for oxygen. During heavy exercise, the demand may be 15 to 25 times greater than at rest. The primary purpose of the cardiorespiratory system is to deliver adequate amounts of oxygen and remove wastes from body tissues, according to momentary need. Further, the circulatory system also transports nutrients and aids in temperature regulation. It is important to remember that the respiratory system and the circulatory system function together as a “coupled unit”; the respiratory system adds oxygen and removes carbon dioxide from the blood, while the circulatory system is responsible for the delivery of oxygenated blood and nutrients to tissues in accordance with their needs. In simple terms, the “cardiorespiratory system” works as a unit to maintain oxygen and carbon dioxide homeostasis in body tissues. A British physician, William Harvey, proposed the first complete theory about how the cardiovascular system works in humans (see A Look Back—Important People in Science).
A LOOK BACK—IMPORTANT PEOPLE IN SCIENCE William Harvey Developed the First Complete Theory of the Circulatory System
William Harvey (1578–1657) was born in England and was educated at both King’s College and the University of Cambridge. He ...