Acid Base balance

Question 1

• Why must the [H+] of body fluids be kept constant?

Answer 1

to avoid detrimental changes in proteins, enzyme

structure and cellular structure.

Question 2

What kind of acid do the kidneys secrete?

Answer 2

Noncarbonic.

Question 3

In the urine secreted H is bound to filtered buffers

such as?

Answer 3

phosphate or ammonia.

Question 4

The kidneys excrete and gain?

Answer 4

NH4+ and there is a

net gain of HCO3- and net loss of H+

Question 5

In the PCT H+ is secreted into the lumen by?

Answer 5

Na+ H+ exchange/antiporter.

Question 6

What other functions occur in the PCT?

Answer 6

Bicarb is exchange across membrane toblood with Na and its this balance that keep pH of blood constant.
Also production of glucose. Glutamate comes from liver.

Question 7

Where is 90% of bicarb reabsorbed?

Answer 7

PCT. This stops carbonic acid accumulating in the lumen and therefore H+ lowered.

Question 8

What are the 4 major factors which control bicarbonate re-absorption are?

Answer 8

*Luminal HC03 concentration
*Luminal flow rate
*Arterial pCO2
*Angiotensin Il (via decrease in cyclic AMP)
An increase in any of these four factors
causes an increase in bicarbonate
reabsorption. Parathyroid hormone also has
an effect: an increase in hormone level
increases cAMP and decreases bicarbonate
reabsorption

Question 9

The distal tubule H + secretion in cortical and medullary collecting tubules by active secretion by H+ ATPases has the primary role in?

Answer 9

Minimising K loss to lumen as it is exchanged for H+.

HTPase is unique to DCT.

Question 10

The ammonia excretion strategies of the PCT are?

Answer 10

Kidney also has ability to excrete H as ammonium.
Ammonium is ionised — fat insoluble and trapped.
New bicarbonate is also generated.
Bicarb absorption and ammonia production get rid of H+.

Question 11

A lower the urine pH does what to ammonium excretion?

Answer 11

The lower the urine pH, the higher the ammonium excretion and this ammonium excretion is augmented further if an acidosis is present.

Question 12

How do tubular cells respond Altered (increased) extracellular pCO2?

Answer 12

—tubular cells respond directly to an
increase in pCO2 of the blood -
respiratory acidosis,
— increase in the rate of H secretion

Question 13

Extracellular fluid volume depletion stimulates?

Answer 13

Sodium reabsorption and increases H+ secretion and HCO3 reabsorption.
By increase of Angiotensin II which stimulates Na+ H+ exchange.
Increase aldosterone levels stimulate H+ secretion by cortical tubules.

Question 14

Hypokalemia stimulates what?

Answer 14

H secretion in the proximal tubule

Question 15

Hyperkalemia inhibits?

Answer 15

H secretion in the proximal tubule.

Question 16

A decreased plasma potassium concentration tends to?

Answer 16

Increase the H concentration in the renal tubular cells.

This, in turn, stimulates H secretion and HCO3 reabsorption and leads to aIkalosis.

Question 17

Hyperkalemia decreases?

Answer 17

H secretion and HCO3 reabsorption and tends to

cause acidosis.

Question 18

Aldosterone stimulates?

Answer 18

promotes na+ and water retention and lowers plasma k+ concentration

Question 19

Angiotensinis a peptide hormone that causes?

Answer 19

vasoconstriction and a subsequent increase in blood pressure. It is part of the renin-angiotensinsystem, which is a major target for drugs that lower blood pressure. Angiotensinalso stimulates the release of aldosterone, another hormone, from the adrenal cortex.