11: Physiology 7

Question 1

What is the equation for pH?

Answer 1

pH = 1 / [H+]

or

pH = -log[H+]

Question 2

What is the average pH of blood?

Answer 2

7.4

Question 3

Why is the pH of venous blood slightly more acidic than the pH of arterial blood?

Answer 3

Venous blood has more CO₂

Question 4

A pH of 7.4 is equal to which concentration of H+?

Answer 4

40 x 10^-9 M

Question 5

Small changes in pH reflect (small / large) changes in [H+].

Answer 5

large changes in [H+]

Question 6

Acidosis causes ___ of the CNS.

Alkalosis causes ___ of the CNS.

Answer 6

acidosis - depression

alkalosis - excitability

Question 7

What

a) sensory
b) motor

symptoms are caused by alkalosis?

Answer 7

a) Pins and needles

b) Spasticity

Question 8

Which important proteins do changes in [H+] have an effect on?

Answer 8

Enzymes

Question 9

What happens to potassium ion concentration in acidosis?

Why?

Answer 9

[K+] increases

As [H+] is secreted by kidneys to compensate, K+ is reabsorbed

Question 10

What is constantly added to the blood by metabolism?

Answer 10

H+

Question 11

What endocrine disease can cause a metabolic acidosis?

What endocrine disease can cause a metabolic alkalosis?

Answer 11

Diabetes

Conn’s syndrome

Question 12

What solutions in the blood resist changes in pH

Answer 12

Buffers

Question 13

What is the equation for the pH at which a buffer system is at equilibrium?

Answer 13

Henderson Hasselbalch

go over principles

Question 14

What does carbon dioxide form when it combines with water?

Answer 14

Carbonic acid

Question 15

Is carbonic acid a strong or weak acid?

Answer 15

Weak acid

so dissociates in solution

Question 16

Which organs regulate

a) [CO₂]
b) [HCO₃^-]?

Answer 16

a) Lungs

b) Kidney

Question 17

For Henderson Hasselbalch

pH = pK + log (kidneys/lungs)

i. e bicarbonate over carbon dioxide
i. e base over acid

Question 18

Which organs regulate bicarbonate concentration?

Answer 18

Kidneys

Question 19

How do you calculate rate of filtration?

Answer 19

ROF = [substance]_plasma x GFR

Question 20

Which enzyme converts carbon dioxide and water to carbonic acid?

Answer 20

Carbonic anhydrase

Question 21

How is bicarbonate reabsorbed by the proximal tubules?

Answer 21

Bicarbonate ions in filtrate combine with hydrogen ions pumped out of tubular cells to form CARBONIC ACID

Carbonic anhydrase converts carbonic acid to CARBON DIOXIDE and WATER

That enters cell, carbonic anhydrase converts it back to CARBONIC ACID

Carbonic acid dissociates into HYDROGEN AND BICARBONATE

H+ pumped out, HCO3- reabsorbed into capillaries

Question 22

What effect does an increase in CO₂ have on

a) H+ secretion
b) HCO3 reabsorption?

Answer 22

Increases both

Question 23

The rate of ___ ___ is greater than the rate of ___ ___.

Answer 23

Rate of hydrogen secretion

is GREATER THAN

Rate of bicarbonate reabsorption

Question 24

What does H+ bind with in the absence of bicarbonate?

When might this occur?

Answer 24

Phosphate

Metabolic acidosis

Question 25

In severely acidotic patients, where all bicarbonate and phosphate has been used up, what combines with H+ ions?

Answer 25

Ammonia

to form ammonium ions

Question 26

In a patient who is severely acidotic, what is excreted in their urine?

Answer 26

Ammonium ions (NH₄⁺)

Question 27

What can be measured in the urine when a patient’s H+ is combining with

a) phosphate
b) ammonia?

Answer 27

a) Titratable acid

b) Ammonium ions

Question 28

Why is bicarbonate ion reabsorption described as unorthodox?

Answer 28

Because the bicarbonate ion found in the filtrate isn’t the one being reabsorbed at the end

Converted to carbonic acid > carbon dioxide + water and back again first

Question 29

reabsorption of bicarbonate

THEN

excretion of acid phosphate

THEN

excretion of ammonium

as acidosis worsens

Question 30

H+ secretion drives ___ ___ to prevent acidosis.

Answer 30

bicarbonate reabsorption

Question 31

What is excreted in the urine to prevent acidosis if bicarbonate stores are used up?

Answer 31

Acid phosphate (titratable acid)

THEN

Ammonium ions