1. Unit Four: The Circulation
Chapter 21: Muscle Blood Flow and Cardiac Output During Exercise; Coronary Circulation and Ischemic Heart Disease
Guyton and Hall, Textbook of Medical Physiology, 12 edition

2. Blood Flow Regulation in Skeletal Muscle
Rate of Blood Flow Through the Muscles
Blood flow through muscle contractions
Increased blood flow in muscle capillaries during
exercise
Fig. 21.1

3. Blood Flow Regulation in Skeletal Muscle
Control of Blood Flow in Skeletal Muscles
Local regulation-decreased oxygen in muscle
greatly enhances flow
Nervous control of muscle blood flow-sympathetic
vasoconstrictor nerves

4. Blood Flow Regulation in Skeletal Muscle
Total Body Circulatory Readjustments During Exercise
Effects of mass sympathetic discharge
Heart is stimulate to an increased rate and increased
pumping strength
Most of the arterioles of the peripheral circulation
are contracted (except those of the active muscles)
Muscle walls of the veins are contracted which
increases the mean systemic filling pressure

5. Blood Flow Regulation in Skeletal Muscle
Total Body Circulatory Readjustments During Exercise
Increase in arterial pressure due to sympathetic
stimulation
Vasoconstriction of the arterioles and small
arteries in tissues other than the active muscles
Increased pumping activity of the heart
Great increase in mean systemic filling pressure

6. Blood Flow Regulation in Skeletal Muscle
Importance of Increase in CO During Exercise
Fig Graphic analysis of change in CO and right atrial pressure with onset of stenuous exercise
Black curve is normal and red cure is strenuous exercise

7. Physiologic Anatomy of the Coronary Blood Supply
Coronary Circulation
Physiologic Anatomy of the Coronary Blood Supply
Fig The coronary arteries

8. Coronary Circulation (cont.)
Normal Coronary Blood Flow-- about 5% of CO
Phasic changes in coronary blood flow during systole
and diastole—effect of cardiac muscle compression
Fig. 21.4

9. Coronary Circulation (cont.)
Epicardial vs. subendocardial coronary blood flow—
effect of intramyocardial pressure
Fig. 21.5

10. Control of Coronary Blood Flow
Local Muscle Metabolism is the Primary Controller
Oxygen demand is a major factor in local coronary
blood flow regulation
Nervous Control of Coronary Blood Flow
Direct effects of nervous stimuli on the coronary
vasculature
b. Sympathetic greater effects than parasympathetic