1. Control of the Internal Environment
Chapter 2
Control of the Internal Environment

2. Homeostasis: Dynamic Constancy
Maintenance of a constant or unchanging “normal” internal environment
Few / mild demands so few responses

3. Homeostasis: Dynamic Constancy
Steady state
Constant internal environment, but not necessarily “normal”
Balance achieved between demands placed on body and the response to those demands

4. Some Examples:

5. Changes in Blood Pressure at Rest

6. Changes in Body Core Temperature During Exercise

8. What controls the system?

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

10. Nature of Control Systems
Most control systems act via negative feedback
Response reverses the initial disturbance in homeostasis

11. Components of a Biological Control System

12. Regulation of Room Temperature: a Non-Biological Control System

13. Example of Homeostatic Control: Regulation of Blood Pressure
Stimulus
Increased blood pressure from HR
Receptors
Baroreceptors in carotid arteries and aorta
Integrating center
Medulla of the brain
Effector
Heart
Response
Decreased blood pumped from heart

14. Example of Homeostatic Control: Regulation of Blood Pressure

15. Example of Homeostatic Control: Regulation of Blood Glucose

17. Nature of Control Systems
Gain of the system
Degree to which the control system maintains homeostasis
System with large gain is more capable of maintaining homeostasis
Large gain = narrow limits
Small gain = wide limits

18. Example of Homeostatic Control: Regulation of Blood Glucose

19. Questions?

20. END