3. Dr FARZANA SALMAN ASSOSIATE PROFESSOR PHYSIOLOGY DEPARTMENT PMC
HOMEOSTASIS
Dr FARZANA SALMAN
ASSOSIATE PROFESSOR
PHYSIOLOGY DEPARTMENT
PMC

4. The Internal Environment
The internal environment or milieu interieur
-Blood plasma
-Intracellular fluid
-Extracellular fluid
The maintenance of a steady state in these fluids is essential to living things

5. HOMEOSTASIS Greek word for ‘same’ and ‘steady’
Any process that living things use to actively maintain fairly stable conditions necessary for survival.

6. Homeostasis
Maintenance of nearly constant conditions of internal environment
Maintenance of environment compatible with life
Essential for survival of each cell
Each cell contribute its part in homeostasis

7. Examples of Homeostasis
Body water regulation by osmoreceptors and kidneys
Excretion of waste products by kidneys and respiration
Temperature regulation
Blood glucose regulation
Maintenance of pH

8. REGULATORY MECHANISM
Intrinsic Control
Extrinsic Control

9. REGULATORY MECHANISM Intrinsic (local)controls
Built in or inherent to an organ e.g CO2 in exercising muscles increase blood flow in the muscle
Extrinsic controls
Initiated outside the organ
Nervous system
Endocrine system

10. REGULATORY MECHANISM Action can be voluntary 1.Drink when thirsty
2.Eat when hungry
3.Put on clothing when cold
4.Open a window when one is too warm
Action can be Involuntary
1.Shivering
2.Sweating

11. SECTIONS OF HOMEOSTASIS
External environment
The Internal environment
Control system

12. Control Systems have two components:
Sensor which detects the change
Effector which corrects the change
Most physiological systems in the body use feedback to maintain the body's internal environment exactly balanced

13. Control of homeostasis
Feedback Systems in Homeostasis
Negative feed back system
Positive feed back system

14. Regulatory Mechanism Negative feed back control
Change in controlled variable triggers a response opposite to the change.
Positive feed back control
Change in controlled variable continues to move in the direction of the change enhancing the change

15. Feedback Systems in Homeostasis
Negative feedback
Used by most of the body's systems
The response caused by the feedback is opposite to the change (stimulus).
↑ Thyroxin → → → → ↓ TSH → ↓ Thyroxin
↓ Thyroxin → → → → ↑ TSH → ↑ Thyroxin

16. -ve feed back control of thyroxin

17. Feedback Systems in Homeostasis
Positive feedback
Control is used in some cases.
The response caused by the feedback is in the direction of the change (stimulus).
Input increases or accelerates the response.
Labor
Oxytocin →↑ uterine contraction →↑Oxytocin

18. Pathophysiology Disruption of Homeostasis Disease
Failure of homeostasis
Death

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