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CP Phys Chap 7
CO2 Transport & Acid-Base Balance Pt 1
| Question | Answer |
|---|---|
| At rest, the metabolizing tissue cells consume and produce what? | Consume 250mL of O2 & produce 200mL of CO2. |
| How many ways does Plasma transport CO2? | 1. Carbamino compound bound to Protein, 2. Bicarbonate, 3. Dissolved CO2. |
| Carbamino compound bound to protein in Plasma | 1% of CO2 transport |
| Bicarbonate in Plasma | 5% of CO2 transport |
| Process of bicarbonate in plasma (very slow process) | CO2 + H2O (Hydrolysis) -> H2CO3 (carbonic acid) -> HCO3- + H+ (ionized ions) |
| Dissolved in Plasma | 5% of CO2 transport |
| Dissolved CO2 in plasma is used to determine what? | Pts. Pco2 (in venous blood) Pco2 x .03 = Pco2 mEq/L |
| How many ways does RBC transport CO2? | 1. Dissolved CO2, 2. Carbamino-Hb, 3. Bicarbonate. |
| Dissolved in RBC | 5% of CO2 transport |
| Carbamino-Hb in RBC | 21% of CO2 transport |
| O2 that is released from the carbamino-Hb reaction is available for what? | Tissue metabolism |
| Bicarbonate in RBC | 63% of CO2 transport |
| Process of bicarbonate in RBC (very fast process) | CO2 + H2O (Hydrolysis) ->(*see Carbonic Anhydrase) H2CO3 (carbonic acid) -> H+ + HCO3- (ionized ions, H+ are buffered by Hb) |
| Carbonic Anhydrase = CA | An enzyme (or catalyst) that greatly enhances the bicarbonate reaction in the RBC causing the RBC to saturate with HCO3- & the excess to diffuse into the plasma. |
| The HCO3- overflow into the plasma does what? | Combines with Na+ to form NaHCO3 and transports HCO3- to the lungs via venous blood. |
| What happens to the Cl from the NaCl in the plasma that the Na left for the HCO3-? | The Cl- movies into the RBC to maintain electric neutrality. Known as the Chloride Shift, or the Hamburger Phenomenon, or as an Anionic Shift to Equilibrium. |
| What happens secondary to the chloride shift? | Some H2O moves into the RBC to preserve osmotic equilibrium causing the RBC to slightly swell in the venous blood. |
| Homeostasis balance ratio in the plasma | 20:1 or HCO3- (20): HcCO3 (1) or Base (20): Acid (1) |
| pH & the plasma ratio | 20:1 keeps pH level w/in normal 7.35 - 7.45 range. Ratio increase = >pH & blood is more alkaline. Ratio decrease = |
| What helps maintain the pH balance and the H+ and HCO3- ion concentrations in blood regulated? | 1. Chemical buffer systems (the 1st line of defense), 2. respiratory system (lungs - regulates CO2), & 3. renal system (kidneys - regulates HCO3- or H+). |
| pH > 7.45 | alkaline, alkalosis, or alkalemia |
| pH < 7.35 | acid, acidosis, or acidemia |
| Buffer is what? | A substance that will neutralize the acids and bases w/out changing the pH. |
| Strong acid does what? | Dissociates completely and irreversibly in water, i.e. HCL -> H+ + Cl-. |
| Weak acid does what? | Does NOT dissociate completely, i.e. H2CO3 -> H+ + HCO3. |
| Strong bases do what? | Dissociates easily and quickly ties up H+, i.e. NaOH -> Na + OH. |
| Weak bases do what? | Dissociate incompletely and reversibly and are slower to accept protons, i.e. NaHCO3- -> Na+ + HCO3-. |
| pH means what? | The negative logarithm, to the base of 10, of the hydrogen ion concentration (H+) in moles per liter, or -log H+. |
| Electrolytes are what? | Compounds, mainly sodium, potassium, magnesium, calcium, chloride, and bicarbonate, that dissociates in fluid into ions capable of conducting electrical currents and is a major force in controlling fluid balance w/ the body. |
| Chemical buffer system | Responds w/in a fraction of a second to resist pH change. It is composed of 1. the carbonic acid-bicarbonate buffer system, 2. the phosphate buffer system, and 3. the protein buffer system. |
| How does the chemical buffer system work? | It inactivates the H+ ions and frees HCO3- ions in response to acidosis. In response to alkalosis it generates more H+ ions and decreases the concentration of HCO3- ions. |
| Respiratory System | It acts w/in 1 to 3 minutes. |
| How does the respiratory system work? | By increasing or decreasing the breathing depth and rate to offset acidosis or alkalosis, i.e. acidosis = inc in depth and rate = body COC2 dec and pH inc, or, alkalosis = dec in depth and rate = body CO2 inc and pH dec. |
| Renal System | Requires a day or more to correct abnormal pH concentrations. It is the body's MOST effective acid-base balance monitor and regulator. |
| How does the renal system work? | When extracellular fluids become acidic it retains HCO3- and excretes H+ ions into the urine causing blood pH to inc. When the fluids become alkaline the system retains H+ and excretes primarily HCO3- into the urine causing blood pH to dec. |
| Henderson-Hasselbalch (H-H)equation | pH = pK + log[HCO3-]/[H2CO3] (base/acid) |
| H-H equation shows what? | How the pH of a solution is influenced by the HCO3- TO H2CO3 ratio. Decrease in ratio (12:1) is a dec in pH. Increase in ration (33:1) is an inc in pH. They are directly related. |
| Values in H-H equation | pH (norm is 7.4) = pK (6.1 is constant) + log[HCO3-] (norm is 24mEq/L)/[H2CO3] (norm is Pco2 x .03 = 40 x .03 = 1.2mEq/L) |
Created by:
mfredenburg
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