1. HomeostasisHomeostasis

2.  Physiology: study the functions of living things

3. Body Fluid Compartments
 Cells contained in watery
internal environment: life-
sustaining exchanges occur
 Extracellular fluid (ECF):
Fluid outside the cells
Plasma
Interstitial fluid
 Intracellular fluid (ICF): Fluid
contained within the cells

4. Homeostasis
 Maintenance of a relatively stable internal
environment
 Internal environment is the extracellular fluid
 Essential for survival and function of all cells

5. Homeostasis
 Factors Homeostatically Regulated:
 Concentration of nutrient molecules
 Concentration of O2 and CO2
 Concentration of waste products
 Concentration of water, salt, and other electrolytes
 Volume and pressure
 pH
 Temperature

6. Homeostasis
 All the systems of the body work together to
maintain homeostasis:
 Gastrointestinal, Respiratory systems Obtaining
nutrients and O2
 Circulatory system  Transport
 Respiratory, Renal systems  Removal of waste and
metabolic end products
 Nervous and Endocrine systems Regulation

7. Homeostasis

8. Homeostatic Control Systems
 Functionally interconnected network of body
components that operate to maintain a given
factor in the internal environment relatively
constant around an optimal level

9. Homeostatic Control Systems
Components:
Sensor: Detects
deviation from set point
Integrating (control)
center: Compares input
with set point &
determines response
Effecter: Produces
response

10. Homeostatic Control Systems
 Feedforward:
 Term used for responses made in anticipation
of a change
 Feedback:
 Refers to responses made after change has
been detected
 Types of feedback systems
 Negative Feedback
 Positive Feedback

11. Homeostatic Control Systems
 Negative Feedback:
 Primary type of homeostatic control
 Opposes initial change

12. Homeostatic Control Systems
 Negative Feedback:

13. Homeostatic Control Systems
 Positive Feedback:
 amplifies an initial change
 An output is enhanced
 A controlled variable moves in the direction
of an initial change

14. Homeostatic Control Systems
 Positive Feedback:
 One example occurs during the birth of a baby

16. Body FluidBody Fluid

17. Body fluid
 On average, body fluids constitute 60% of total
body weight
 In the average 70 Kg adult male is about 42 L

18. Body fluid
 Variation in water content:
 Variation due to age: total body water (TBW)  with
increasing age, by age of 60 years it becomes 50 %
 Variation between tissues:
 Most tissues are water-rich and contain 70-80% water
 Plasma contains >90% water
 Fat is the driest tissue of all, having only 10% water
content
 Variation between individuals:
 TBW in a standard male is 60% of his body weight, while
in female, its 55%, due to higher fat content
 Obese adults have lower percentage

19. Body Fluid Compartments
 TBW represent about 60% of total body weight:
 Intracellular fluid (ICF):
 fluid within the cells
 about 2/3 of TBW (40%)
 Extracellular fluid (ECF):
 fluid outside the cells
 About 1/3 of TBW (20%)

20. Body Fluid Compartments

22. Body Fluid Compartments

23. Body Fluid Compartments

24. Body Fluid Compartments

25. Body Fluid Compartments

26. Body Fluid Compartments
ICF differs considerably from ECF

27. Body is in fluid balance
 Daily intake of water:
 Fluid intake (1.250 mL/day)
 Food intake (1000 ml/day)
 Metabolically produced H2O
(350mL/day)
 Daily loss of body water:
 Insensible water loss
(900ml/day)
 Fluid loss in sweat
(100ml/day)
 Water loss in feces
(100ml/day)
 Water loss by kidney (1500
ml/day)
Total intake (2600ml/day) Total output
(2600ml/day)

31. Body is in fluid balance
 In a steady state, the osmolarity in ECF is the
same as in ICF
 Normally, cells neither shrink or swell because
intracellular and interstitial fluids have the same
osmolarity (280 mmol/L)
 Increasing osmolarity of ECF draws water out of
cells and cells shrink
 Decreasing osmolarity of ECF draw water inside of
cells and causes cells to swell