PDF Working Copy Outline Chapter 8

PDF Working Copy Outline Chapter 8 - Topic 8 Regulation of...

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Topic 8 Regulation of Acid-Base Balance Acid-base balance is concerned with maintaining a normal H + ion concentration in the body fluids. How is this balance achieved? - Two mechanisms for buffering: - - pH of Body Fluids The H+ concentration of the body fluids is extremely low. - Arterial blood: 40 nEq/L (40 x 10 -9 ) Because of low concentration, H + concentration is expressed as the negative logarithm, or pH: pH = - log 10 [H + ] The normal H+ concentration of 40 x 10 -9 Eq/L is converted to pH as follows: pH = - log 10 [40 x 10 -9 Eq/L] = 7.4 All cells, tissue, and organ processes are sensitive to pH. Body fluid pH ranges from 6.8 to 7.8 - Life cannot exist outside of this range. The normal range of arterial pH is 7.32 to 7.42 Essential for all cellular functions Alkalemia: Acidemia: Three mechanisms contribute to maintaining pH in the normal range: 1. 2. 3.
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The HCO 3 - Buffer System What is a buffer? What is the most important buffer of the ECF? Plasma has a concentration of 23 to 25 mEq/L of HCO 3 - and a volume of 14L - can potentially buffer 350 mEq of H + Unlike the other buffer systems of the body (e.g., PO 4 3- ), the HCO 3 - buffer system is regulated by both the lungs and kidneys CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - Carbonic anhydrase In alveoli (lungs); in epithelial cells of renal tubules Carbonic Anhydrase Deficiency -Deficiency of this enzyme is characterized by: 1. 2. 3. The two components of the HCO 3 - buffer system are regulated: - - This regulation allows precise control of the pH of the ECF by: - - Side note: Acid: A substance that adds H + to body fluids Alkali: A substance that removes H + from body fluids
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Henderson-Hasselbalch Equation Used to quantitate the impact of changes in CO 2 and HCO 3 - on pH. pH = pK + log [HCO 3 - ] α P CO 2 pH = 6.1 + log [HCO 3 - ] 0.03 P CO 2 P C O 2 = partial pressure of CO 2 α = solubility of CO 2 At 37 ° C, solubility of CO 2 in plasma ( α ) = 0.03 pK = 6.1 K = equilibrium constant pK = - log 10 K (pH units) [HCO 3 - ] regulated by kidney PCO 2 in ECF: by rate of respiration Metabolic acid-base disorder Which organs regulate plasma HCO 3 - ? When does metabolic acid-base disorder occur? Respiratory acid-base disorder Which organ controls PCO 2 ? Metabolic production of Acid and Alkali Nutrients when oxidized, generate CO 2 and H 2 O 15-20 moles of CO 2 /day generated, which is effectively expired from the lungs. - No impact on acid-base balance Two kinds of acids Volatile acid - Nonvolatile or fixed acid - In order to maintain acid-base balance, acid must be excreted from the body at a rate equal to its addition. Acidosis –
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This note was uploaded on 01/07/2012 for the course PHCH 6234 taught by Professor Farqui during the Winter '11 term at Palmer Chiropractic.

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PDF Working Copy Outline Chapter 8 - Topic 8 Regulation of...

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