1. Chapter 2 Control of the Internal Environment
EXERCISE PHYSIOLOGY
Theory and Application to Fitness and Performance, 6th edition
Scott K. Powers & Edward T. Howley

2. Objectives Define the terms homeostasis and steady state
Diagram and discuss a biological control system
Give an example of a biological control system
Explain negative feedback
Define what is meant by the gain of a control system

3. Homeostasis: Dynamic Constancy
Maintenance of a constant internal environment
Steady state
Balance between the demands placed on a body and the physiological response to those demands

4. Body Core Temperature During Exercise
Fig 2.2

5. Blood Pressure at Rest
Fig 2.3

6. Control Systems of the Body
Goal
To regulate some physiological variable at or near constant value

7. Non-Biological Control System
 in room
Temperature
below 200 C
Room Temperature
Signals thermostat
To turn off heat
Room
temperature
Returns to 200 C
Thermostat set
at 200 C
Heating System
Fig 2.4

8. Biological Control Systems
Series of interconnected components that serve to maintain a physical or chemical parameter at or near constant
Receptor
Capable of detecting changes
Integrating center
Assesses input and initiates response
Effector
Corrects changes to internal environment

9. Components of a Biological Control System
Fig 2.5

10. Negative Feedback Most biological control systems
Response reverses the initial disturbance in homeostasis

11. Gain of a Control System
Gain of the system
Degree to which the control system maintains homeostasis
System with large gain is more capable of maintaining homeostasis

12. Example: Regulation of Blood Pressure
Fig 2.6

13. Example: Regulation of Blood Glucose
Fig 2.7

14. Example: Cellular Stress Response
Fig 2.8

15. Exercise: A Test of Homeostatic Control
Submaximal exercise in a cool environment
The body’s control systems can maintain steady state
Maximal exercise or exercise in a hot/humid environment
May not be able to maintain steady state
Severe disturbances in homeostasis can occur

16. Chapter 2 Control of the Internal Environment