Copyright © 2008 Thomson Delmar Learning CHAPTER 18 Exercise and Its Effects on the Cardiopulmonary System
Copyright © 2008 Thomson Delmar Learning VENTILATION
Copyright © 2008 Thomson Delmar Learning CONTROL OF VENTILATION
Copyright © 2008 Thomson Delmar Learning Mechanisms by Which Exercise Stimulates Ventilation Fig Mechanisms by which exercise stimulates ventilation. (1) Collateral fibers form the motor neurons travel to the medulla; (2) sensory signals from the exercising limbs are sent to the medulla; the increase in body temperature during exercise may also increase ventilation.
Copyright © 2008 Thomson Delmar Learning ALVEOLAR VENTILATION
Copyright © 2008 Thomson Delmar Learning Exercise and Ventilation Fig The relationship of exercise and ventilation. Note the abrupt increase in ventilation at the outset of exercise (A) and the even larger, abrupt decrease in ventilation at the end of exercise (B).
Copyright © 2008 Thomson Delmar Learning OXYGEN CONSUMPTION
Copyright © 2008 Thomson Delmar Learning Oxygen Consumption (VO 2 ) and Alveolar Ventilation Fig There is a linear relationship between oxygen consumption (VO 2 ) and alveolar ventilation as the intensity of exercise increases.
Copyright © 2008 Thomson Delmar Learning Oxygen Consumption When anaerobic threshold is reached during strenuous exercise –Linear relationship between VO 2 and alveolar ventilation will no longer exist. When the anaerobic threshold is reached –Abrupt increase in alveolar ventilation with little or no increase in VO 2.
Copyright © 2008 Thomson Delmar Learning Arterial Blood Gas Levels During Exercise Fig The effect of oxygen consumption on PaO 2 and PaCO 2 as the intensity of exercise increases.
Copyright © 2008 Thomson Delmar Learning OXYGEN DIFFUSION CAPACITY
Copyright © 2008 Thomson Delmar Learning Oxygen Diffusion Capacity Fig Oxygen diffusion capacity increases linearly in response to increased oxygen consumption as the intensity of exercise increases.
Copyright © 2008 Thomson Delmar Learning Alveolar-Arterial PO 2 Difference Fig The alveolar- arterial oxygen tension difference P(A-a)O 2 begins to increase when approximately 40 percent of the maximal VO 2 is exceeded.
Copyright © 2008 Thomson Delmar Learning Circulation During exercise, three essential physiologic responses must occur for the circulatory system to supply working muscles with an adequate amount of blood: 1.Sympathetic discharge 2.Increase in cardiac output 3.Increase in arterial blood pressure
Copyright © 2008 Thomson Delmar Learning At the onset of exercise, the brain transmits signals to the vasomotor center, which has two circulatory effects: –The heart is stimulated to increase its rate and strength of contraction. –Blood vessels of the peripheral vascular system constrict, except for blood vessels of the working muscles. Sympathetic Discharge
Copyright © 2008 Thomson Delmar Learning Cardiac Output Increased oxygen demands during exercise are met almost entirely by an increased cardiac output.
Copyright © 2008 Thomson Delmar Learning Cardiac Output Fig A linear relationship exists between cardiac output and the intensity of exercise.
Copyright © 2008 Thomson Delmar Learning Cardiac Output Increased cardiac output during exercise results from: 1.Increased stroke volume 2.Increased heart rate, or 3.Combination of both
Copyright © 2008 Thomson Delmar Learning Increased Heart Rate An individual’s maximum heart rate (MHR) is estimated as follows:
Copyright © 2008 Thomson Delmar Learning Increased Heart Rate Thus, the maximum heart rate for a 45-year-old person is about 175:
Copyright © 2008 Thomson Delmar Learning Arterial Blood Pressure There is an increase in arterial blood pressure during exercise because of the: 1.Sympathetic discharge 2.Increased cardiac output 3.Vasoconstriction of the blood vessels in the nonworking muscle areas
Copyright © 2008 Thomson Delmar Learning Venous Vascular Pressure An oxygen consumption and cardiac output increase during exercise Mean pulmonary arterial and wedge pressure also increase linearly
Copyright © 2008 Thomson Delmar Learning Pulmonary Arterial and Wedge Pressure Fig The systolic, diastolic, and mean pulmonary arterial and wedge pressure increase linearly as oxygen consumption and cardiac output increase.
Copyright © 2008 Thomson Delmar Learning Muscle Capillaries At rest, about 20 to 25 percent of the muscle capillaries are dilated During heavy exercise, capillaries dilate to facilitate distribution of blood This reduces the distance that oxygen and other nutrients must travel from the capillaries to the muscle fibers
Copyright © 2008 Thomson Delmar Learning INTERRELATIONSHIPS BETWEEN MUSCLE WORK, OXYGEN CONSUMPTION, AND CARDIAC OUTPUT
Copyright © 2008 Thomson Delmar Learning Muscle Work, Oxygen Consumption, and Cardiac Output Fig Relationship between muscle work, oxygen consumption, and cardiac output.
Copyright © 2008 Thomson Delmar Learning THE INFLUENCE OF TRAINING ON THE HEART AND CARDIAC OUTPUT
Copyright © 2008 Thomson Delmar Learning Stroke Volume Versus Heart Rate and Cardiac Output Fig Approximate changes in stroke volume and heart rate that occur when the cardiac output increases from about 5 L/min to 30 L/min in a marathon runner.
Copyright © 2008 Thomson Delmar Learning BODY TEMPERATURE/ CUTANEOUS BLOOD FLOW RELATIONSHIP
Copyright © 2008 Thomson Delmar Learning Cardiopulmonary Rehabilitation Phase I Phase II Phase III