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U N I T I
Textbook of Medical Physiology, 11th Edition
GUYTON & HALL
Copyright © 2006 by Elsevier, Inc.
Chapter 1:Functional Organization of the Human Bodyand Control of the “Internal Environment”
Slides by John E. Hall, Ph.D.
Copyright © 2006 by Elsevier, Inc.
Physiology
The science that is concerned with the functionof the living organism and its parts, and of the physical and chemical processes involved.
• Human Physiology
Copyright © 2006 by Elsevier, Inc.
• The study of disordered body function (i.e. disease)
• The basis for clinical medicine
Pathophysiology
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The Human Body - A ComplexSociety of Differentiated Cells
• Cells: the basic structural and functional unit(~ 100 trillion)
• Tissues: (e.g. muscles, epithelial, nervous )
• Organs: (e.g. kidney, heart, liver, pancreas)
• Organ systems: (e.g. cardiovascular, urinary)
Copyright © 2006 by Elsevier, Inc.
Regulation and Integration
• Exists at all levels of organization
• Cells: e.g., genes, operons, repressor proteins, transcription factors, membrane transport
• Tissues: e.g., autacoids, paracrines• Organ systems: e.g., nervous and endocrine
systems
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Homeostasis
The maintenance of a stable“ milieu interieur”
Claude Bernard (1813 - 1878)
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Figure 1-1;Guyton & Hall
General Organizationof the Circulatory
System
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Figure 1-2; Guyton & Hall
Exchange Between the Capillaries and Interstitial Fluid
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Feedback Control
• Negative feedback: promotes stability
• Feed-forward: anticipates change
• Positive feedback: promotes a change in one direction, instability, disease
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Negative Feedback Control of ArterialPressure Promotes Stability
Art. Pressure SympatheticActivity
Heart RateVasoconstriction
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Baroreceptor Reflex : Negative Feedback System - Promotes Stability
Blood vessels, Heart
Baroreceptors
Set-point
Error signal
VasomotorCenters
Sympathetic System
Effectors
BloodPressure
SensorControlled Variable
+
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Cardiopulmonary Reflexes:Feed-Forward Control of Blood Pressure –Anticipates a Change
Blood vessels, Heart
Baroreceptors
Error signal
VasomotorCenters
Sympathetic System
Effectors
BloodPressure
SensorControlledVariable
Set-point
Cardiopulmonary Receptors
Cardiopulmonary Pressures
+
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Feedback Gain
A measure of the effectiveness of a feedback system
Gain =Correction
Error
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What is the feedback gain in this example ?
Hemorrhage 1.5 liters
100
50
75Arterial Pressure
feedback “correction”
= - 25
“ error ”= + 25
Gain =Correction
Error=
- 25
25= - 1.0
Copyright © 2006 by Elsevier, Inc.
Feedback and Feed-Forward Control
• Negative feedback: promotes stability
• Feed-forward: anticipates change
• Positive feedback: promotes a change in one direction, instability, disease
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Positive Feedback of Hemorrhagic Shock
Figure 1-3;Guyton & Hall
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Hemorrhagic Shock:Positive Feedback
Severe Hemorrhage
Venous ReturnCardiac Output
Blood Pressure
Coronary Blood Flow
Cardiac Contractility
+
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Action Potential:Positive Feedback
Cell Depolarization
Cell Na Permeability
Na Influx
Cell Membrane Potential
+