1. Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – 422222, India

2. OC-SEP033-CP01-04 Introduction Programmes and Courses  SEP – SBT033 – Unit 01  SEP – SBI033 – Unit 01  SEP – SGS033 – Unit 01

3. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.3 Credits  Academic Inputs by Arun Punaji More. M.Sc. (Microbiology) Experience: 11 Years arunmesh@hotmail.com

4. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam.

5. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to: Describe optimum physiological range of acid base in human body. Explain the importances of acid base balance. Explain the mechanisms of regulation of acid base balance.

6. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.6 Introduction  In human body concentraton of H + ions and OH- ions keep changing due to various metabolic as well as physiological process.  Normal functioning of enzymes require H+ and OH- ions concentration in optimum range.  For example for normal functioning of enzymes H + ions concentration has to maintained in a very tight range with optimum concentration at 0.00000004 Eq/L.  In this presentation you will learn various mechnisms of maintaining H+ ions conc.

7. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.7 Normal Acid Balance-1  Each day 80 milliequivalent of hydrogen is produced by ingestion and metabolism.  The extracellular concentration of H + ions has to be 0.00000004 Eq/L. For normal functioning of enzymes.  Since due to this cumbersome value, the H + ions concentration is expressed in logarithmic term using pH unit.  The pH unit is defined as the negative log of H+ H + ions concentration.  pH= log1/[H + ] = -log[H + ] = - log[0.00000004] = 7.4

8. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.8 Normal Acid Balance-2  The pH of arterial blood is 7.4.  The pH of venous blood and interstitial fluid is 7.35.  The condition in which there is decrease in pH below from its normal value of 7.4 is referred as acidosis.  The condition in which there is increase in pH above from its normal value of 7.4 is referred as alkalosis.

9. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.9 Normal Acid Balance-3  The lowest pH at which person can survive a few hour is 6.8.  The highest pH at which person can survive a few hour is 8.0.  The pH of intracellular fluid remain in range of 6.0 to 7.4 due intense metabolic activities which produce acids.

10. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.10 Regulation of H + ions Conc.-1  The acid base balance is maintained in very tight range as described previously by following system in body. Buffer system, Proteins, Lungs (by increasing respiration rate), Kidney.

11. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.11 Regulation of H + ions Conc.-2  Regulation of H + ions conc. By Buffer system:- Buffers are substances which resist any change in pH by reacting with the increased H + ions or OH - ions. There are two buffer systems operating to maintain the pH of extra cellular fluids. These buffer systems are bicarbonate buffer system and phosphate buffer system. Bicarbonate buffer:-  The ingredients of bicarbonate buffer system are weak acid H 2 CO 3 and its salt with a strong base, NaHCO 3 in water.  H 2 CO 3 is formed in lung by the reaction of CO 2 with water; the reversible reaction is catalyzed by carbonic anhydrase present in lungs. CO 2 +H 2 O  H 2 CO 3 ------------I

12. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.12 Regulation of H + ions Conc.-3  H 2 CO 3 formed in this way ionizes as follow: H 2 CO 3 H + +HCO 3- ----------II  When H + ions increase in extra cellular fluid, they react with the HCO 3- ions shifting the equilibrium to the left side forming H 2 CO 3 in reaction no. II.  The increased concentration of H 2 CO 3 shift the equilibrium to left in reaction no. I forming CO 2 and H 2 O; these excess CO 2 is expelled by respiratory system as higher concentration of CO 2 in extra cellular fluid stimulates increase in respiration rate.  Thus the change in pH is nullified.

13. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.13 Regulation of H + ions Conc.-4 The another ingredient of bicarbonate buffer is sodium bicarbonate, NaHCO 3 present in extra cellular fluid. NaHCO 3 ionizes in reversible manner as follow: NaHCO 3 +HCO 3- + Na + ---III Now consider reaction no. I and II together; you will see that the relative concentration of HCO 3- ions increases than that of H + ions; this help to reduce increased concentration of H + ions in the extra cellular fluids.

14. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.14 Regulation of OH - ions Conc.-1 When OH - ions increases, either after addition of a base, H 2 CO 3 react with OH - ions as shown below: NaOH + H 2 CO 3 NaHCO 3 + H 2 O ------IV The NaHCO 3 formed as above dissociate as shown in reaction no. III. And extra HCO 3- ions formed thus are excreted by kidney.

15. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.15 Regulation of OH - ions Conc.-2  Phosphate buffers:- Phosphate buffer system play important role in maintaining pH of intracellular fluid and renal tubular fluid. The main ingredients of phosphate buffer are H 2 PO 4 - and HPO 4 -2. When H + ions increase after the addition of HCL, Na 2 HPO 4 react with H + ions forming NaH 2 PO 4. When OH + ions increase after the addition of NaOH, NaH 2 PO 4 react with OH + ions forming Na 2 HPO 4. The phosphate buffers are efficient buffer in intracellular fluid due to its pK of 6.8 to normal pH of 7.4.

16. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.16 Proteins as Buffers  Proteins account for 60% to 70% buffering power within cytoplasm of cells.  Proteins act as good buffers in intracellular environment as their Pks values of most of the proteins are close to normal physiological pH i. e. 7.4 of the body.

17. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.17 Regulation of pH by Lungs-1  Regulation of H + ions conc. By Lungs:-  CO 2 is continually produce in metabolic processes inside the cells; this CO 2 is then rapidly diffuses into interstitial fluid and finally come into blood.  Increased concentration of CO 2 in interstitial fluid, increases H + ions conc. in extra cellular fluid as per the reaction no. 1 and 2.  Therefore to decrease the H + ions conc. Expulsion of CO 2 is achieved by increasing ventilation by lungs; this task is the rapid and efficient way of lowering H + ions conc. to maintain the pH of extra cellular fluid.  Decreased in pH due to higher CO 2 in interstitial fluid stimulate higher ventilation by lungs to expel CO 2.

18. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.18 Regulation of pH by Lungs-2  Relationship between alveolar ventilation and pH change:

19. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.19 Regulation of pH by Lungs-3  Reduced alveolar ventilation increases blood pH:-

20. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.20 Regulation of pH by Kidneys  The main action kidneys carried out to maintain the normal range of pH in the body is by excretion of acid or base whose concentration is increased.  If concentration of acid H + ions increases in extra cellular fluid then kidney excrete H + ions, at the same time kidneys reabsorb bicarbonates which are filtered out through the kidney tubules and produce new bicarbonate adding into blood.  If concentration of base increases in extra cellular fluid then kidney excrete HCO 3 - ions.  Kidneys mainly involved in excretion of non-volatile acids other than H 2 CO 3 because they are not excreted by lung as described previously.

21. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.21 What We Learn…..  Homeostasis of acid base balance in body.  Role of various buffers in homeostasis of acid base.  Role of kidney in maintaining pH of body.  Role of lungs in maintaining pH of body.

22. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.22 Critical Thinking Question  Why life expectancy is reduced to a few years in patient whose kidneys are partially failed to work?

23. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.23 Tips for Critical Thinking Question  Major direct roles of kidneys in maintaining acid base balance in body.  Major indirect role of kidneys in maintaining blood pressure of the body.

24. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.24 Study Tips  Book Title:Textbook of medical physiology. Dr. Arthur C. Guyton, John E. Hall. Author: Dr. Arthur C. Guyton, John E. Hall. Publication: Elsevier India Private Limited.  Book Human Physiology Title: Human Physiology C. C. Chattergy. Author: C. C. Chattergy. -- Publication: --

25. End of the Presentation Thank You!