1. Homeostasis

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 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 between tissues:
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
Extracellular fluid:
Plasma :
Liquid part of the blood
Inside the blood vessel (intra vascular)
¼ of ECF
Interstitial fluid:
baths all the cells in the body and is the link between ICF and intravascular compartment
¾ of ECF
Transcellular fluid:
Small fluid volumes secreted by specific cells into a cavity, to perform a specialized function
It includes CSF, GIT fluids, aqueous humor and joint fluid
Lymph:
The fluid being returned from the interstitial fluid to the Plasma by lymphatic vessels

22. Body Fluid Compartments

23. Body Fluid Compartments

24. Body Fluid Compartments
Barrier between plasma and interstitial fluid:
The blood vessels walls separate the plasma and interstial fluid
Water and all plasma constituents except plasma proteins are freely exchanged between plasma and interstial fluid, across the thin permeable capillary walls
Therefore, the plasma and interstial fluid are similar in composition, except that interstial fluid lacks plasma protien

25. Body Fluid Compartments
Barrier between the ICF and ECF:
The ECF is separated from ICF by the cell membrane
This membrane is highly selective (permits some stuff, but excludes others)
ICF contains proteins that cannot permeate through the cell membrane, due to their size
There is an unequal distribution of cations and anions between ECF & ICF

26. Body Fluid Compartments
The main cation in ECF is Na + and the main anion in ECF is CL -
The main cation in ICF is K + and the main anion in ICF is phosphate ions
Protein content of ICF is more than ECF
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)

29. Osmolarity – refers to the number of solute particles per liter of solution expressed as osmoL/L
The higher the osmolarity the higher the concentration of solutes (the lower H2O concentration)
When solution osmolarity is compared to that of the cell, its either
Iso-osmotic
Hypo-osmotic
Hyper-osmotic
Water tend to move by osmosis down
its own concentration gradient from
an area of lower solute concentration ( higher H2O concentration) to an area of higher solute concentration ( lower H2O concentration)

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