Transcript Unit One: Introduction to Physiology: The Cell and

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
Blood Flow Regulation in Skeletal Muscle
• Rate of Blood Flow Through the Muscles
a. Blood flow through muscle contractions
b. Increased blood flow in muscle capillaries during
exercise
Fig. 21.1
Blood Flow Regulation in Skeletal Muscle
• Control of Blood Flow in Skeletal Muscles
a. Local regulation-decreased oxygen in muscle
greatly enhances flow
b. Nervous control of muscle blood flow-sympathetic
vasoconstrictor nerves
Blood Flow Regulation in Skeletal Muscle
•Total Body Circulatory Readjustments During Exercise
a. Effects of mass sympathetic discharge
1. Heart is stimulate to an increased rate and increased
pumping strength
2. Most of the arterioles of the peripheral circulation
are contracted (except those of the active muscles)
3. Muscle walls of the veins are contracted which
increases the mean systemic filling pressure
Blood Flow Regulation in Skeletal Muscle
•Total Body Circulatory Readjustments During Exercise
a. Increase in arterial pressure due to sympathetic
stimulation
1. Vasoconstriction of the arterioles and small
arteries in tissues other than the active muscles
2. Increased pumping activity of the heart
3. Great increase in mean systemic filling pressure
Blood Flow Regulation in Skeletal Muscle
•Importance of Increase in CO During Exercise
Fig. 21.2 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
Coronary Circulation
• Physiologic Anatomy of the Coronary Blood Supply
Fig. 21.3 The coronary arteries
Coronary Circulation (cont.)
•
Normal Coronary Blood Flow-- about 5% of CO
a. Phasic changes in coronary blood flow during systole
and diastole—effect of cardiac muscle compression
Fig. 21.4
Coronary Circulation (cont.)
b. Epicardial vs. subendocardial coronary blood flow—
effect of intramyocardial pressure
Fig. 21.5
Control of Coronary Blood Flow
•
Local Muscle Metabolism is the Primary Controller
a. Oxygen demand is a major factor in local coronary
blood flow regulation
•
Nervous Control of Coronary Blood Flow
a. Direct effects of nervous stimuli on the coronary
vasculature
b. Sympathetic greater effects than parasympathetic