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Flashcards in Physiology 5 Deck (29):
1

Plasma buffer system equation?

HCO3- + H+ H2CO3

2

What is the first line of defence in terms of protecting against acidosis/alkalosis?

Buffers

3

What are the relative concentrations of bicarbonate and carbonic acid?

26mM 3uM

4

what is the equation which controls the amount of carbonic acid in the blood?

CO2 + H2O H2CO3 Equalibirum is far towards CO2 Very slow reaction Needs carbonic anhydrase Particularly high in RBCs

5

What enzyme converts carbonic acid?

Carbonic anhydrase

6

What is the effective buffer system between?

Bicarbonate and carbon dioxide (dray out equation)

7

What is the pK of CO2 and HCO3-?

6.1

8

What would be the ideal pK of a buffer?

7.4

9

What organ controls bicarbonate?

Kidneys

10

Henderson-Hasselbalch equation:

pH = pK + log {[base]/ [acid]}

11

What is the role of the lungs in altering pH?

Alter pCO2 through changes in ventilation

12

What is the role of the kidneys in altering pH?

–Alter HCO3- by changes in production & excretion –Alter pH by changes in H+ excretion

13

Aside from buffers what else can buffer the blood?

Plasma proteins

Phosphate (HPO4/H2PO4)

Heamoglobin (very high buffering ability)

Buffering is just a temporary solution

14

What reaction takes place with CO2 in the RBC?

CO2 + H2O H2CO3 (Carbonic anhydrase)

15

What acids to the kidneys deal with?

Sulphuric and phosphoric acids from proteins and lipids.

Lactic acid from anaerobic metabolism

Keto acids from fatty acids

16

Why does the kidney need to deal with acids?

There are a number of non-volatile acids (i.e. cannot breath them out). Relatively a lot less than CO2

17

How much acid to the kidneys deal with each day?

70 mmol of strong acid per day

18

What is the hallmark of a metabolic acidosis?

Decrease in a bicarbonate level

19

What happens with regard to pH with prolonged diarrhoea?

Metabolic acidosis due to loss of bicarbonate

20

What happens with vomiting with regard to pH?

Metabolic alkalosis

21

What is the anion gap?

If we add Na and K HCO3 and Cl It is found that the gap is about 10mmol

22

What is the most important contribution to the anion gap?

Proteins

23

What causes a high anion gap?

• Lactic acidosis (lactic acid) • Diabetic ketoacidosis (keto-acids) • Renal failure

24

What are the renal compensations in an alkalosis?

Reduced acid excretion Excretion of bicarbonate

25

What is the renal response to acidosis?

Increased acid secretion Increased HCO3 re-absorption and production

26

How is bicarbonate reabsorbed?

Proton secretion into the tubule

27

Where are hydorgen ions secreted?

Proximal tubule Distal tubule Collecting duct

28

Steps bicarbonate reabsorption and acid excretion

Na+/H+ antiport secretes H+

H+ in filtrate combines with filtered HCO3- to form CO2

CO2 diffuses into cell and combines with water to from H+ and HCO3-

H+ is secreted again and excreted

HCO3- is reabsorbed

Glutamate is metabolized to ammonium ion and HCO3-

NH4+ is secreted and excreted

HCO3- is reabsorbed

A image thumb
29

What happens to secreted hydrogen ions?

There is a lot of carbonic anhydrase and will convert it into water and produce a CO2