Chapter 1: Functional Organization of the Human
Body and Control of the “Internal Environment”
Guyton and Hall, Textbook of Medical Physiology, 12 edition
Human Physiology
The attempt to explain the specific characteristics and
mechanisms of the human body that make it a living being.
1. Cells: the living units of the body
•Each organ is an aggregate of many different cells held
together by intercellular supporting structures
•All cells have certain basic characteristics
•Almost all cells have the ability to reproduce
2. Extracellular Fluid—The “Internal Environment”
• Intracellular Fluid-fluid within the cell
• Extracellular Fluid-found in the spaces outside the cells
a) Constant motion throughout the body
b) Contains the ions and nutrients cells need
c) Called the “internal environment”
Differences Between Intracellular and Extracellular Fluids
Extracellular Fluid:
•Contains large amounts of Na+, Cl-, and bicarbonate ions
•Contains nutrients such as oxygen, glucose, fatty acids,
and amino acids
•Contains carbon dioxide and other cellular wastes
Intracellular Fluid:
•Contains large amounts of K+, Mg+, and phosphate ions
Homeostatic Mechanisms
The maintenance of nearly constant conditions
in the internal environment.
•
Extracellular fluid transport and mixing
system:
a. Blood Circulatory System
•
Origin of nutrients in the extracellular fluid
a. Respiratory system
b. Gastrointestinal tract
c. Liver and other metabolic organs
d. Musculoskeletal system
Homeostatic Mechanisms (cont.)
• Removal of metabolic end products
a. Removal of carbon dioxide by the lungs
b. Kidneys
c. GI tract and the liver
• Regulation of body functions
a. Nervous system
b. Endocrine system
•
Protection of the body
a. Immune system
b. Integumentary system
•
Reproduction
Control Systems of the Body
•
Examples of control systems
a. Regulation of oxygen and carbon dioxide in the
extracellular fluid
b. Regulation of arterial blood pressure
c. Normal ranges and physical characteristics of
extracellular fluid components
Normal Value
Range
Non-lethal
Limits
Unit
Oxygen
40
35-45
10-1000
mm Hg
Carbon dioxide
40
35-45
5-80
mm Hg
Sodium ion
142
138-146
115-175
mmol/L
Potassium ion
4.2
3.8-5.0
1.5-9.0
mmol/L
Calcium ion
1.2
1.0-1.4
0.5-2.0
mmol/L
Chloride ion
108
103-112
70-130
mmol/L
Bicarb. Ion
28
24-32
8-45
mmol/L
Glucose
85
75-95
20-1500
mg/dl
Body Temp.
37
37
18.3-43.3
C
Acid-Base
7.4
7.3-7.5
6.9-8.0
pH
Control Systems of the Body (cont.)
•
Characteristics of control systems
a. Negative feedback
b. Positive feedback
c. Adaptive control