1. Homeostasis

2. At the end of presentation,students should be able to
Describe homeostatic mechanisms of the major functional systems.
Describe control systems of the body
Examples of control mechanisms
Characteristics of control mechanism

3. Homeostasis
Homeostasis, from the Greek words for "same" and "steady," refers to any process that living things use to actively maintain fairly stable conditions necessary for survival.

4. Homeostasis
Homeostasis mean maintenance of nearly constant conditions in the internal environment.
60% of adult human body is fluid,1/3 is ECF, contains ions and nutrients,internal environment of the body.
Concept by Claude Bernard, French physiologist of 19th century
Name- American physiologist Walter B. Cannon.

5. THE INTERNAL ENVIRONMENT
The internal environment or milieu interieur
Extracellular fluid
Importance

7. ECF fluid transport and mixing system: 2 stages: 1
ECF fluid transport and mixing system: 2 stages: 1. Movement of blood in the blood vessels 2. Fluid movement in between blood capillaries and the intercellular spaces between the tissue cells.

9. Blood circulates once each min throughout the body at rest and six times each min when active. Large amount of fluid and dissolved constituents diffuse back and forth between blood and tissue spaces.

10. Origin of nutrients in the ECF
Respiratory system:
Blood picks up O2 in the alveoli
Alveolar membrane 4-2 micrometers thick
GIT:
Carb, fatty acid, amino acids absorbed from the ingested food into the ECF of the blood.
Liver:
Change chemical composition of many absorbed substances to more usable forms.

12. Removal of metabolic end products
Removal of carbon dioxide by the lungs
Removal of urea, uric acid by the kidneys and also excess of ions and water.

13. COMPOSITION OF BODY FLUIDS

15. COMPOSITION OF BODY FLUIDS
CATIONS (mmol/l)
Plasma
Interstitial
Intracellular Na
142
139 14 K
4.2
4.0
140 Ca
1.3
1.2 Mg
0.8
0.7 20
ANIONS (mmol/l) Cl
108
HCO3
24.0
28.3 10
Protein
0.2
HPO4
2.0 11 O2

16. Essentials of homeostasis
Conc of oxygen and carbon dioxide
pH of the internal environment
Concentration of nutrients and waste products
Conc of salts and electrolytes
volume and pressure of ECF
Temperature regulation

17. EXAMPLES OF HOMEOSTASIS
Body water regulation by osmoreceptors and kidneys.
Excretion of waste products by kidneys and respiration
Temperature regulation
Blood glucose regulation
Constant supply of nutrients
Maintenance of pCO2 and pO2
Maintenance of pH

18. Homeostasis is
Essential for survival of each cell
Each cell contribute its part in homeostasis
Interdependent relationship of all cells, body systems and homeostasis

19. Regulation of body functions by the major systems

20. The major systems Cardiovascular system Transportation
O2, CO2, nutrients, waste products, hormones etc
Digestive system
Digestion, Absorption of nutrients, excretion of wastes
Transfer of materials from external environment to internal environment
Respiratory System :
Supply O2 of & elimination of CO2
Acid base balance

21. The major systems Urinary System Elimination of waste products
Water & electrolytes balance
Acid base balance
Blood pressure regulation
Skeletal system
Support & protection
Movement
Reservoir for calcium

22. The major systems Muscular system
Movements towards or away from different elements
Most of the voluntary movements by skeletal muscles
Integumentary system
Protection
Temperature regulation
Immune System
Defense against foreign invaders
Defense against Cancer

23. The major systems Nervous System Control system of the body
Coordination of body activities
Quick response to stimuli
Consciousness, memory and intellectual functions
Endocrine System
Another major control system
Control of metabolism
Control of nutrients supply, storage and utilization
Reproductive system
Reproduction – continuation of life

25. Regulatory Mechanism
Most physiological systems in the body use feedback to maintain the body's internal environment exactly balanced

26. EXAMPLES of control mechanism
Oxygen buffering function of hemoglobin
Baroreceptor system as rapidly acting mechanism to decrease high blood pressure
Regulation of Carbon dioxide conc in ECF

27. Normal ranges and physical characteristics of important ECF constituents:
Increase in body temperature by 11 degrees F (7 degrees C)___Increase in cellular metabolism----cell destroys. pH K+ Ca Gl

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

29. Regulatory Mechanism Negative feed back control
System reacts in such a way as to arrest the change or reverse the change.
Positive feed back control
System reacts in such a way as to enhance or amplify the change in the same direction.

30. 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

31. Negative feed back control of thyroxin

32. Examples of negative feed back control:
High conc. of carbon dioxide initiates events that decrease the concentration towards normal.
High AP causes a series of reactions that lead to lowered pressure. This effect is negative with respect to the initiating stimulus.

33. 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.

35. Positive feed back
Labor Oxytocin →↑ uterine contraction →↑Oxytocin
Clotting
Generation of nerve impulses
Useful positive feedback itself is part of an overall negative feedback process.

36. Feed forward control
Sensory nerve signals from the moving parts apprise the brain whether movement is performed correctly. If not , the brain corrects the feed forward signals that it sends to the muscles the next time the movement is performed. This is called adaptive control and is a delayed negative feedback.

37. Pathophysiology Disruption of Homeostasis Failure of homeostasis
Disease Death