Physiology 7

Question 1

normal blood pH?

Answer 1

7.35-7.45

venous blood = 7.35 due to higher CO2 concentration

Question 2

small changes in pH reflect large changes in [H+], true or false?

Answer 2

true

Question 3

why is blood pH important?

Answer 3

acidosis can depress CNS
alkalosis can overexcite the peripheral NS and later the CNS
[H+] affects enzyme activity and K+ levels in the body
- high H+ secretion = low K+ secretion = potassium retention

Question 4

H+ is continuously added to the body via what 3 sources?

Answer 4

carbonic acid formation
inorganic acids produced during breakdown of nutrients
organic acids resulting from metabolism (fatty acids, lactic acid etc)

Question 5

how is diabetes mellitus related to [H+]?

Answer 5

sufferers metabolise fat instead of glucose which produces ketoacids

Question 6

strong vs weak acids in solution?

Answer 6

strong = dissociate completely in solution
weak = only dissociate partly in solution

Question 7

what is a buffer system and what does it consist of?

Answer 7

first line of defence for pH change
compensates for change in pH of body fluids
consists of a pair of substances
- one which yields free H+ as [H+] decreases
- other binds free H+ when [H+] increases

Question 8

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Answer 8

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Question 9

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Answer 9

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Question 10

what happens if base is added to buffer system?

Answer 10

base it tied up by combining with H+, allowing more HA to dissociate
[HA] falls and [A-] falls
- i.e ……

Question 11

dissociation constant=?

Answer 11

K = [H+][A-] / [HA]
pK = -logK

Question 12

how is pH calculated from pK?

Answer 12

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Question 13

most important buffer I the body?

Answer 13

CO2 - HCO3 buffer
CO2 + H2O <> H2CO3 <> H+ + HCO3
- catalysed by carbonic anhydrase

Question 14

CO2 and HCO3 concentrations are controlled by what?

Answer 14

CO2 = lungs
HCO3 = kidneys
pH = pK + log kidneys/lungs?

Question 15

describe the role of the kidneys in control of [HCO3]

Answer 15

variable reabsorption of filtered HCO3
kidneys can also add new HCO3 into the blood (more HCO3 in renal vein than renal artery)
both are driven by H+ secretion into the tubule

Question 16

why is reabsorption of HCO3 important?

Answer 16

counteracts acid

if none was reabsorbed, would be like adding 4 L of 1M HCl to the body every day

Question 17

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Answer 17

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Question 18

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Answer 18

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Question 19

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Answer 19

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Question 20

more hydrogen ions are secreted than bicarbonate is reabsorbed, true or false?

Answer 20

true

Question 21

when is this not true?

Answer 21

when HCO3 being used to buffer an acidosis, needs to be replenished
when HCO3 is low due to reabsorption, H+ then combines with phosphate instead (as its the 2nd most plentiful)

Question 22

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Answer 22

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Question 23

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Answer 23

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Question 24

how can titration be used?

Answer 24

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Question 25

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Answer 25

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Question 26

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Answer 26

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Question 27

3 functions of H+ secretion?

Answer 27

drives bicarbonate ion reabsorption
drives formation of acid phosphate (can be measured as titratable acid which allows formation of 1 bicarbonate into blood)
drives formation of ammonia which also allows formation of new bicarbonate into the blood

Question 28

secretion of how many H+ ions equates to production/reabsorption of 1 HCO3 or production of 1 acid phsopahte or 1 ammonium?

Answer 28

1

Question 29

daily summary?

Answer 29

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