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Homeostasis Maintenance of relatively stable internal environment.

Homeostasis Maintenance of relatively stable internal environment. At the end of the class, student should be able to. - Define homeostasis. - Explain different control mechanisms involved in homeostasis with examples. - Classify body fluid compartments and to quantify them. HOMEOSTASIS.

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Homeostasis Maintenance of relatively stable internal environment.

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  1. Homeostasis Maintenance of relatively stable internal environment.

  2. At the end of the class, student should be able to - Define homeostasis. - Explain different control mechanisms involved in homeostasis with examples. - Classify body fluid compartments and to quantify them.

  3. HOMEOSTASIS Homeostasis is the maintenance of a steady state in the body despite changes in the external environment The steady state is the optimum level for the body functions

  4. HOMEOSTASIS – REGULATION OF INTERNAL CONDITIONS • The term “milieu interieur” was coined by Claude Bernard. • The actual environment of the body cells is the interstitial component of the extracellular fluid (ECF) • The term “homeostasis” was coined by WB Cannon in 1929 to mean constancy of the internal environment after its distortion by external stresses. 

  5. HOMEOSTASIS – REGULATION OF INTERNAL CONDITIONS • Regulation of fluid, electrolytes and acid-base balance is concerned with total body water (TBW), and concentrations of substances distributed between different fluid compartments. • Maintaining homeostasis or constancy of the internal environment is a function of many organ systems. •   It follows that malfunction of any of them can disturb fluid, electrolyte, and acid-base balance.  

  6. Homeostasis depends on feedback circuits • Three components Receptor – detects a change in internal environment Control Center – process information from receptor, directs signal to the effector Effector – brings about the change to normal condition.

  7. Negative feedback control system • Cause and response are in opposite direction. • The sensor detects deviations from normal set point. • Signals from the sensor trigger compensatory changes that continue until the set point is again reached • The response to the initiating stimulus is negative.

  8. Secretion of insulin entry of glucose to peripheral tissue Increase in blood sugar level Blood sugar to cause or stimulus normal level response /effect

  9. Positive feedback control system • Response is in the direction of stimulus. • Amplifying system. • Each successive cycle shall be stronger than previous cycle. • Ex: Parturition, Milk ejection reflex, Blood coagulation.

  10. Positive Feedback: Blood Clotting

  11. Body composition • In average young adult male:

  12. TOTAL BODY WATER (TBW) • 60% OF THE BODY WEIGHT IN ADULT MALE • 50% OF THE BODY WEIGHT IN ADULT FEMALE

  13. FLUID COMPARTMENTS EXTRA CELLUAR FLUID INTRA CELLULAR FLUID INTERSTITIAL FLUID • PLASMA TRANSCELLULAR FLUID • CSF • Intra ocular • Pleural • Peritoneal • Synovial • Digestive Secretions

  14. Body Fluids • Water content in body is divided into 2 compartments: 1. Extracellular fluid (ECF): (internal environment or the milieu intérieur) • Fluid outside the cells. • ECF=14 liters • 20% of body weight • Interstitial fluid between cell is 80% of ECF. • Plasma in blood is 20% of ECF • Also includes lymph, cerebrospinal fluid, synovial fluid, aqueous humor, vitreous body, endolymph, per lymph, pleural, pericardial, and peritoneal fluids

  15. 2. Intracellular fluid (ICF): - Fluid inside the cells. - ICF=28 liters. 40% 0f body weight.

  16. Blood Total Body Water ECF ECF BLOOD Interstitial Interstitial ICF ICF ICF

  17. VOLUME OF BODY FLUIDS IN 70 kg MAN TOTAL VOLUME 42 L INTRA CELLUAR FLUID 28 L(ROUGHLY 2/3 OF TBW) EXTRA CELLULAR FLUID 14 L(ROUGHLY 1/3 OF TBW) PLASMA 4 L (ROUGHLY ¼ OF ECF)

  18. COMPOSITION OF BODY FLUIDS

  19. MEASUREMENT OF BODY FLUID COMPARTMENT INTERSTITIAL FLUID ECF – Plasma Volume INTRACELLULAR FLUID TBW – ECF

  20. VOLUME MEASUREMENT OF VARIOUS FLUIDS COMPARTMETNS • Dye Dilution Principle • TOTAL BODY WATER (TBW) • SUBSTANCE USED • DEUTERIUM OXIDE (D2O) • TRITIATED WATER • ANTIPYRINE • AMINOPYRINE

  21. VOLUME MEASUREMENT OF VARIOUS FLUIDS COMPARTMETNS • EXTRACELLUR FLUID • SUBSTANCES USED : TWO MAJOR TYPES: • SACCHARIDES e.g. SUCROSE, INULIN, MANNITOL • DIFFUSIBLE IONS e.g. SULPHATE, SODIUM, THIOSULPHATE, BROMIDE, CHLORIDE

  22. VOLUME MEASUREMENT OF VARIOUS FLUIDS COMPARTMETNS BLOOD PLASMA. • EVAN’S BLUE • RADIOACTIVE LABELLED 125 I ALBUMIN TOTAL BLOOD VOLUME PLASME VOL X 100 100 -HCT

  23. THANK YOU

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