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Flashcards in Acid- Base Balance Deck (8)
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1

ACIDS

- Chemical species capable of releasing hydrogen (H+)ions into water
- pH is a measure of the concentration of H+ in a solution

2

BUFFERS

- Means by which a solution resists changes in pH
- Examples of buffers in the body; proteins, phosphate buffer system,carbonic acid/bicarbonate buffer

3

THE CARBONIC ACID/BICARBONATE BUFFER SYSTEM

- Most important one in the body is carbonic acid
- Carbonic dioxide + water ← → carbonic acid ← → bicarbonate + hydrogen ions
- These reactions occur spontaneously
- Carbonic anhydrase is an enzyme found in parts of the body including rbc and kidneys
- It accelerates the reversible reactions between carbon dioxide and water and carbonic acid

4

REGULATION OF BODY FLUID pH

- Throughout the body: hydrogen ions are neutralised via action of buffers

2 compensatory mechanisms are used to regulate blood pH
- Removal of CO2 from body via lungs
- Secretion of H+, reabsorption of HCO3 in kidneys

5

REGULATING pH BY BUFFERS

- If pH decreases; the increase in H+ in the body fluids will see a shift from right to left leading to a rise in pCO2 (blood carbon dioxide level)

6

REGULATING pH BY RESPIRATORY COMPENSATION

- If pH decreases; the increase in H+ in the body fluids will see a shift from right to left leading to a rise in pCO2 (blood carbon dioxide level)
- The carbon dioxide is removed from the body via lungs→ therefore to deal with rise of H+ in the body fluids→ there needs to be greater work down by lungs
- If pH is too high; equation will shift from left to right to make up from shortfall in H+, pCO2 will drop and respiratory rate will fall allowing CO2 to build up back in the blood

7

REGULATING pH BY RENAL COMPENSATION

- In the kidneys excess H+ ions are secreted into the urine as the filtrate travels through the tubules
- Also the kidneys will reabsorb bicarbonate from the filtrate and so prevent its loss in the urine
- These 2 processes principally involves the carbonic acid/bicarbonate buffer reaction
- Evidence for this being the pH of urine from a healthy person commonly has a pH lower than blood

8

BRINGING IT ALL TOGETHER

3 tiers of regulation of acid- base balance
Buffer systems
The Lungs
The Kidneys

- Buffer systems regulate acid- base balance in the very short term; by utilising substances that can bind to either an acid or base
- When the carbonic acids dissociates into carbon dioxide and water, we breathe this out through the lungs, ridding the body of the acid
- Long term control of acid- base balance is managed by the kidneys, as they can adjust the pH over a long period of days by either retaining bicarbonate ions and excreting hydrogen ions