Respiration Lecture 11: Resp. Acid-Base Balance Flashcards Preview

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Flashcards in Respiration Lecture 11: Resp. Acid-Base Balance Deck (62):
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Acid

molecules containing H+ atoms that can be released into solutions. HA in HH equation.

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Base

ion or molecule that can accept a H+ atom. A- in HH equation

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When is buffer system most resistant to changes in H+?

When pH = pK

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Normal extracellular pH range

7.35-7.45

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3 main mechanisms to keep pH within normal limits

1) extracellular buffering (don't actually remove H+ from system)
2) adjustments to blood PCO2 by altering the ventilatory capacity of the lungs (<---THE MAIN METHOD...KNOW!)
3) adjustments to renal acid excretion or base reabsorption

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Acidemia

acidic blood (high H+ conc.)

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Alkalemia

alkaline blood (low H+ conc.)

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where is H ion state measured?

receptors in CSF

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weak acid or base

acid or base that incompletely dissociates. (pK is such that it doesn't completely dissociate)

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buffer

reduces changes in pH resulting from the addition of strong acids or bases

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What is greatest source of H+?

CO2 (via oxidation of glucose and fatty acids during metabolism)

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CO2 is an example of what type of acid?

volatile acid

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Non-volatile acids that are sources of H+ in metabolism

sulfuric, phosphoric, hydrochloric, and lactic acids

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The #1 blood buffer

Bicarbonate ***** Most important because the buffered H+ ion it can carry can be removed by both the renal and respiratory systems

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Other blood buffers besides bicarbonate

phosphate, proteins

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Henderson-Hasselbalch Equation

HA H+ + A- and pH = pKa + log [A-]/[HA] DNK

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how many pH units around pK can buffer act?

+/- 1 pH unit

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Buffer strength is directly proportional to ?

concentration of paired buffer components

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Non-bicarbonate buffer systems

Phosphate buffer system
Protein buffer system

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Bicarbonate buffer system ****

utilizes carbonic anhydrase reaction to maintain blood pH. carbon dioxide (CO2) combines with water to form carbonic acid (H2CO3), which in turn rapidly dissociates to form hydrogen ions and bicarbonate (HCO3- ) as shown in the reactions below. The carbon dioxide - carbonic acid equilibrium is catalyzed by the enzyme carbonic anhydrase; the carbonic acid - bicarbonate equilibrium is simple proton dissociation/association and needs no catalyst. An OPEN SYSTEM via elimination of CO2 and H+ to the environment

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Carbonic anhydrase reaction

CO2 + H2O H2CO3 H+ + HCO3-

CO2 = acid (proton donor)
HCO3 = base (proton acceptor)
H+ = free proton responsible for setting pH

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If alveolar pressure decreases due to hypoventilation, what happens to pH?******

increase in PCO2, so pH decreases (increase in H+)

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Phosphate buffer system reaction

H2PO4 H+ + HPO4

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What happens to acidity of Hb as O2 leaves?

Decreases

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deoxyhemoglobin

Hb that is desaturated of O2

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Hb protein buffer system

Hb becomes more acidic when it binds O2, allowing less CO2 to be transferred as bicarbonate and vice versa.

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Which two organs regulate the bicarbonate buffer system?

lungs and kidneys

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Only way to ELIMINATE H+ ?

via blown off CO2 or renal excretion

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most important blood borne protein buffer

Hb

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protein with highest conc. in blood

Hb

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Is Hb classified as extracellular or intracellular?

extracellular

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Where is phosphate buffer system strongest and why?

kidney. Env. is more acidic and phosphate is higher

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How does bicarbonate buffer system compensate for its low pK?

By being an open system

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organ that releases the largest amount of acid

resp. system

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primary body systems that regulate H+

respiratory, renal, and gastrointestinal

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How does removal of CO2 also remove H+?

For every molecule of CO2 eliminated, an H+ is bound to H2O removing it from solution

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2nd most important buffer in the body

proteins (ex: Hb, myoglobin)

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Increasing V'A --> PaCO2?

decrease

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Respiratory acidemia

low pH due to change of breathing. A retention of CO2 generally caused by respiratory problems such as hypoventilation

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Respiratory alkalemia

high pH due to change of breathing. Excessive loss of CO2 generally caused by hyperventilation

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Metabolic acidemia

low pH due to change in body metabolism

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Metabolic alkalemia

high pH due to change in body metabolism

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How does bicarb. buffer system react to increased acid?

driving force to L. More CO2 will be released by lungs via increased ventilation (i.e. "ketone breathe")

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How does bicarb. buffer system react to increased CO2?

driving force to R. More HCO3- removed by kidneys

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low pH, high PaCO2 indicates:

respiratory acidemia

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high pH, low PaCO2 indicates:

respiratory alkalemia

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low pH, low PaCO2 indicates:

metabolic acidemia

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high pH, high PaCO2 indicates:

metabolic alkalemia

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High PaCO2 --> HCO3- concentration?

also high.

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blood buffer line on Davenport diagram represents:

buffering capacity of blood

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4 types of acid-base disturbances

respiratory acidemia
respiratory alkalemia
metabolic acidemia
metabolic alkalemia

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How is respiratory acidemia compensated?

metabolically (i.e. kidney retain base HCO3-)

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How is respiratory alkalemia compensated?

metabolically (i.e. kidney loses net base HCO3-)

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FIRST priority in compensating for an acid-base disturbance

Restore pH

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possible causes of metabolic acidemia

diabetes, heart failure, renal failure, diarrhea. Addition/retention of non-volatile acid, or loss of base.

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possible causes of metabolic alkalosis

loss of non-volatile acid, intake of base. I.e. - vomiting

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Compensation for metabolic acidemia

respiratory compensation. Lungs excrete more CO2 via hyperventilation

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Compensation for metabolic alkalosis

respiratory compensation. Lungs excrete less CO2 via hypoventilation

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*Review Davenport Diagram in notes*

:)

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Possible causes of respiratory acidosis

insufficient ventilation, CNS depression, obesity, etc.

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Possible causes of respiratory alkalosis

CNS mediated hyperventilation, peripheral stimulation of ventilation, hypoxemia, pregnancy, etc.

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pH =

-log[H+]. Also, pH = constant + Kidneys/Lungs

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