Physio 7

Question 1

Which blood is more acidic : arterial or venous blood?

Answer 1

Venous blood as it contains more the CO2 and forms carbonic acid

Question 2

What is the normal pH levels in the body?

Answer 2

7.35-7.45

hence average 7.4

Question 3

What is the ECF H+ concentration for a plasma pH of 7.4

Answer 3

40 nmol

Question 4

What is the ECF H+ concentration for a plasma pH of 7.0

Answer 4

100 mnol/l

Question 5

How does a small change in the pH affect the H+ concentration?

Answer 5

very large chnages in the H+ concentration

Question 6

What does acidosis do?

Answer 6

Depression of the CNS

Question 7

What does alkalosis do?

Answer 7

Alkalosis can lead to overexcitability of the peripheral NS and later the CNS.

muscle twitching and spams –> if extreme can affect the respirtatory system

Question 8

How does H+ changes affect the K+ levels in your body?

Answer 8

If we are acidotic –> increases H+ secretion –> decrease in K+ secretion –> K+ retention increased

Question 9

How if H+ added to the body?

Answer 9

continuously as a result of metabolic activity

1. Carbonic acid formation
2. Inorganic acids produced during breakdown of nutrients (meat on breaking)
3. Organic acids resulting from metabolism (keto acids, lactic acids)
4. Diabetes mellitus(Cells metabolise fat –> increased production of keto-acids –> yield H+ –> disrupt ppH balance)

Question 10

How does DM cause acidosis?

Answer 10

Cells metabolise fat –> increased production of keto-acids –> yield H+ –> disrupt ppH balance

Question 11

What do strong acids dissociate to?

Answer 11

dissociate completely

Question 12

What do weak acids dissociate to?

Answer 12

dossciate partially

Question 13

What is the first line of defense against any change in pH levels?

Answer 13

Buffer system

Question 14

What happens if increased H+ added?

Answer 14

Protons are “mopped-up” by A- leading to formation of more HA

[HA] rises, [A-] falls

In other words, the rise in [H+] (fall in pH) has been limited (buffered) by the formation of HA

Question 15

what happens if more A- added?

Answer 15

Base is “tied-up” by combining with H+, allowing more HA to dissociate

[HA] falls, [A-] rises

In other words, the rise in pH (fall in [H+]) has been limited (buffered) by further dissociation of HA

Question 16

What is the important buffer system in the body?

Answer 16

Carbon dioxide - bicarbonate system

Question 17

What regulstes the plasma concentration of bicarbonate

Answer 17

Kidney

Question 18

What regulates the partial pressure of co2 levels in the body?

Answer 18

Lungs

Question 19

What is the role of the kidney in the control of bicarbonate?

Answer 19

1.Variable reabsorption of filtered HCO3-

2. Kidneys can add “new” HCO3- to the blood
   i. e. [HCO3-]renal vein > [HCO3-]renal artery

Higher concentration of bicarbonate as it is secreted by the tubule and can then be added to the blood

Question 20

What drives the reabsorption of the generation and reabsorption of bicarbonate ions in the kidney?

Answer 20

H+ ions

Question 21

What is the importance of reabsorbing HCO3- ions?

Answer 21

if not it would be equivalent to adding about 4 litres of 1M HCl to the body

Question 22

What is t

Answer 22

40 nmol/L of H+

Question 23

Concentration of H+ or HCO3-(24 mmol/L) is more in the plasma?

Answer 23

HCO3- is more

Question 24

Why is the rate of filtration of H+ less?

Answer 24

hydrogen ions in the plasma low hence the filtration of H+ is also low

no apical transpot mechanism to move HCO3- from the tubular fluid to the cells - hence indirect methoud of reabsorption

Question 25

How does the reabsorpotion of HCO3 - occur?

Answer 25

Indirect method depending on the H+ concentration

Question 26

How is HCO3- reabsprtbed?

Answer 26

H+ (from the dissociation of carbonic acid) secreted across the apical membrane into the fluid in exchange for sodium for the na/ H+ exchanger the bicarbonate ions makes its way into the interstitial fluid via the exchanger at the basolateral membrane bicarbonate disappears from the tubular fluid and is seen in the interstitial fluid (not the same though as what it was in the beginning)

Question 27

What drives the H+ ion secretion in the proximal tubule?

Answer 27

CO2 increased CO2 retention --> increased H+ secretion

Question 28

Is H+ secreted more or HCO3- filtered more?

Answer 28

renal tubular cells secrete more H+ ions than HCO3- that are filtered normally reabsorb all the filtered HCO3 -

Question 29

Formation of new HCO3-

Answer 29

if you reduce the plasma concentrattion of HCO3- ions, then the concentration of the tubular fluid of HCO3- also increases (as rate of F = plasma conc x GFR) instead of combining with HCO3-, H+ combines with the PO4

Question 30

Where is the phosphate present from?

Answer 30

Breakdwon of protein

Question 31

Ways to secrete H+ in the collecting duct cells

Answer 31

H+/K= ATPase or H+ ATPase

Question 32

What happens if HCO3- levels are low?

Answer 32

in bicarbonate levels are low --> H+ combines with pO4 and formed H2PO4 once bicarbonate ion formed for each H+ added to the tubular fluid Bicarbonate helps to replenish the buffer stores

Question 33

What is titratable acid?

Answer 33

The amount of hydrogen phosphate excreted

Question 34

what is the maximin titratable acid that can be exctreted from the kidney?

Answer 34

40 mmol/.day

Question 35

What is the amount of bicarbonate that is added to the blood?

Answer 35

40 mmol/.day (as the amount of HCO3- ions added is the same as the H+ ions secreted)

Question 36

What happens if acidosis persists even after all the phosphate levels are depleted?

Answer 36

breaks down ammonium via glutamine and add H+ to it to form Ammonium and one HCO3- added for each ammonium ion added

Question 37

What is the normal level of ammonium that is excreted from the blood per day?

Answer 37

20 mmol/L

Question 38

What are the 3 functions done by H+ secretion in the tubule?

Answer 38

1. HCO3- ion reabsorption 2. Drives the formation of acid phosphate which adds one HCO3- back to the blood 3. During acidosis, it can form NH4 and adds one HCO3- ions back to the blood

Question 39

What is the level of NH4 in someone with acidosis?

Answer 39

5-600 mmol/day

Question 40

What is the amount of HCO3- generated?

Answer 40

it it

Question 41

if acidotic

Answer 41

increase ammonium and hydrogen phsophate secretion

Question 42

What is the amount of HCO3- newlygenerated?

Answer 42

the amount of H+ excretion (TA excretion + NH4 excretion)