Acid Base Balance

Question 1

Small changes in pH have….

pH equation

Most bodily fluids are

1 unit pH change equals

Answer 1

A big effect on bodily function

pH= -log10 H+

7.35-7.45.
Other outliers are 6.8-8.

x10 change in H+

Question 2

Fluctuations in H+ will affect

Answer 2

Excitability of muscles and nerves
Enzyme activities
K levels.

Question 3

The pH at the start of a capillary is

And at the end it’s

Answer 3

7. 45

7. 35

Question 4

7. 45+ means

7. 35- means

Answer 4

Alkalosis.

Acidosis

Question 5

Body fluids that are outliers in the normal pH range.

Answer 5

Gastric secretions 0.7

CSF 7.3

Pancreatic secretions 8.1

Final urine 5.4

Question 6

Sources of acid and alkali

Answer 6

Metabolism produced a large amount of acid.
15 mol is CO2 a day.
40nmol of H+ a day
Protein rich western diet is very high in H+

There is alkali in fruit
Lose 10mmol of OH a day

Net excess acid 70mmol a day.

Question 7

Buffer systems

Answer 7

Blood and tissue buffers take seconds to respond.

Respiration takes minutes to respond.

Renal takes hours or days to respond. And is the only one for the extrusion of acid or alkali.

Question 8

Where are buffers present

Examples

Answer 8

Blood
Extracellular fluid
Intercellular fluid
Urine

Haemoglobin
HCO3
Inorganic phosphate
Weak acids and bases on proteins.

Question 9

The carbonic acid and bicarbonate buffer system.

Eg increase CO2

Answer 9

The reaction is in equilibrium.
CO2+H2O = H2CO3 = H + HC03-

An increase in CO2 will acidify the system and shift the equilibrium to the right.
More CO2 will bind with H20 and make more H2CO3 which will make H and HC03-
This will lower the pH.

Question 10

Henderson hasselbach equation

Answer 10

pH = pk + log HCO3/H2CO3

pk is a constant at 37 degrees of 6.1.

H2CO3 is equal to CO2. This rule is needed for this equation.

Normally there is x20 more HC03 than CO2.

So 6.1 + log (20/1) = 7.4. Normal pH

Question 11

What happens when you add acid to the body.

Answer 11

The H conc goes up.
The pH goes down

H binds to HCO3 and makes H2CO3.
Which will make CO2 and H2O.
The HCO3 conc goes down when it makes H2CO3.

Causing metabolic acidosis. Which is low pH and low HCO3.

Question 12

What happens when you add base to the body.

Answer 12

HCO3 conc goes up.
pH goes up.

H will bind to the extra HCO3.
This will make H2CO3 and then H20 and CO2.

The H conc goes down as it binds to all the extra HCO3.

Causes metabolic alkalosis which is high pH and high HCO3.

Question 13

Removing CO2 from the body

Answer 13

This will shift the equilibrium to the left.
More H and HCO3 will combine to make H2CO3 and then more CO2 and H2O to replace the lost CO2.

The HCO3 and H conc will go down giving a high pH.

Respiratory alkalosis. High pH but low HCO3

Question 14

Adding CO2 to the body

Answer 14

The equilibrium shifts to the right.

More CO2 and H2O are making H2CO3.
Which makes more H and HCO3.

This gives a high H and a low pH. And it makes a high HCO3 conc.

Respiratory acidosis.

Question 15

What does the chemical control of ventilation do

Answer 15

Controls blood gas composition

Negative feedback

Triggered by hypoxia and hypercapnia or acidosis.

This will cause increase in ventilation and lead to correction of the problems.

Question 16

Peripheral chemoreceptors

Glomus cells

Answer 16

Found in carotid body and aortic arch.

Stimulated by hypoxia mainly.

They send signals through the sinus, vagus and Glossopharyngeal nerve to the medulla and respiratory centre. To regulate respiration.

Glomus cells pick up hypoxia and can fire action potentials to stimulate the vagus, sinus and glossopharyngeal nerve.

Question 17

Structure of carotid body chemoreceptor.

Answer 17

Small 2mg

High blood flow x40

High metabolic rate

Glomus cells fire potentials

Type 2 cells five structural support.

Symp and para axons regulate flow.

Question 18

Mechanism of glomus cell action

Answer 18

Low oxygen or high CO2 or pH causes block of BK K channels in glomus cell.

Causes depolarisation and action potential.

Opens Ca channels. And high Ca allows ntm release.
The ntm binds to afferent neurons and activates them.

Question 19

SIDS babies

Answer 19

Sudden instant death syndrome babies.

Unknown reason.

In carotid bodies have too much NA and dopamine and disrupt the breathing pattern.

Question 20

What happens if a person has hypoxia hypercapnia and a low pH

Answer 20

Even more impulses are fired

Question 21

Central chemoreceptors and what they are activated by

CO2 increase from 40 to 45

Answer 21

Activated by hypercapnia. It detects the H levels and not the actual CO2.

Amount of CO2 increases from 40 to 45 will cause doubled ventilation.

They are located in the brain parenchyma and are bathed by brain extra cellular fluid.
They are separated from the blood by the BBB which has poor ion permeability.
H and HCO3 can’t cross but CO2 can.

So high CO2 is detected.

Question 22

Buffering power in the BECF

Answer 22

There is less buffering capacity in the BECF due to no bicarb and less proteins.

This means they can’t help as much to maintain pH.
A drop in the pH in the plasma will be a lot less than in the BECF due to less buffering power.

This allows the central chemoreceptors to be extremely sensitive to changes in pH.

Question 23

How can chronic acidosis be helped using the BECF

How do respiratory and metabolic acidosis differ in the BECF

Answer 23

Making the barrier allow more HCO3 into the BECF.

Resp acidosis is caused by high CO2 which can enter the BBB.
Metabolic acidosis is caused by H and HCO3 which cannot enter the BBB.
This means that metabolic disorders hardly effect the pH of the BECF and resp acidosis has a big effect.

Resp acidosis will increase the pH 10-35 times more than metabolic.

Question 24

What is sitting in the BECF

What neural populations does it contain.

Link to SIDS babies

Answer 24

Ventrolateral medulla and other brainstem nuclei.

Acid activated neurons release seratonin
Acid inhibited neurons release GABA.

Some babies lack seratonergic neurons so will have a defect in central chemoreceptors and can stop breathing.

Question 25

The peripheral and central chemoreceptors responding together. If there is low oxygen and CO2 If oxygen is normoxic Which receptors are used in metabolic acidosis

Answer 25

Peripheral do O2 Central do CO2. Peripheral respond first. Even larger increase in ventilation. Central chemoreceptors will do 60-85% if the work. Acute cases use peripheral. Chronic cases use central To increase ventilation.

Question 26

Kussmaul breathing

Answer 26

Hyperventilation

Question 27

How do renal mechanisms help What are the mechanisms

Answer 27

Long term regulation Removes acid and alkali directly. HCO3 handling Urine acidification Ammonia synthesis

Question 28

HCO3 handling Where does it happen What’s the mechanism

Answer 28

90% happens in the proximal tubule. 10% at the distal tubule. There is reabsorption of all filtered bicarbonate. In the proximal cell. Apical membrane has an Na/H exchanger so Na enters the cell and H leaves. The H makes H2CO3 with a HCO3. This splits into H20 and CO2 which can enter the cell. CARBONIC ANHYDRASE Inside the cell it makes H2CO3 and then HCO3 and H. The HCO3 can now be reabsorbed into the blood. In the distal tube it’s the same but there is a H pump instead of the Na\H

Question 29

Base conservation: What are the two ways and what percentage of the work do they do.

Answer 29

Urine acidification 25% Ammonia synthesis 75%

Question 30

Urine acidification What molecules are involved What else is made by proximal cells

Answer 30

Alkaline salt + H = acid salt. Na2HPO4 = NaH2PO4 The alkaline salt loses a Na which enters the proximal cell and allows a H to leave. The H combines with the alkaline salt and replaces the Na. The NaH2PO4 is excreted in the urine. Acid phosphate, uric acid, creatine New HCO3

Question 31

Ammonia production How is NH3 made in the body Why is this so effective

Answer 31

NH3 + H = NH4+ Ammonia is permeable and ammonium is not. Glutamine forms alpha ketoglurarate which makes NH3 and H. Glutamine in cells makes H and NH3 which both leave the cell through the apical membrane. H uses the transporter and NH3 is permeable. They combine to make NH4 outside the cell. This cannot re enter and is excreted. 4 H are gone at once so very effective.

Question 32

What are the renal responses to acidosis.

Answer 32

H excretion methods are up regulated. This takes hours or days for new proteins to be made. Keep the normal 100% HCO3 reabsorption. The pH of urine will go down and it will help the acidosis

Question 33

What are the renal responses to alkalosis

Answer 33

H excretion methods are down regulated. Slight excretion of HCO3 This will help to lower the pH.

Question 34

What can cause respiratory acidosis. What are the symptoms and why What will the renal system do

Answer 34

Problems with CO2 elimination causing high CO2. Such as lung disease emphysema and chronic bronchitis. More CO2 means more H2CO3 made which will break down and give off more HCO3 and H. There will be a low pH and a high HCO3, and a high CO2. Secretes more H. pH goes back up. Reabsorbs more HCO3 and makes more new HCO3 the proximal cells.

Question 35

What causes respiratory alkalosis Symptoms and why What will the renal system do

Answer 35

Too much removal of CO2 due to hyperventilating and fear or stress. Low CO2 means the equilibrium will shift to make more CO2. H and HCO3 combine to make H2CO3. Which makes more CO2 and H2O. This will use up the H so the pH goes up. Symptoms are high pH and low HCO3 and CO2. Secretes less H. The H combines with HCO3 and makes H2CO3. This makes more water and CO2. This will decrease the pH because more CO2 and more H.

Question 36

What causes metabolic acidosis Symptoms How does respiration help How does the renal system help

Answer 36

Acid ingestion or loss of alkaline fluid. Diarrhoea, cholera, diabetic ketoacidosis. High H will bind to all the HCO3 and so HCO3 conc will go down. CO2 is normal. Increase respiration to decrease CO2 and increase the pH. This is because the loss of CO2 will shift the equilibrium to make more CO2 and use up all of the H. Increase H secretion More HCO3 reabsorption

Question 37

What causes metabolic alkalosis Symptoms How does respiration help. What does the renal system do

Answer 37

Ingestion if alkaline fluid or loss of acid from vomiting. High pH and high HCO3. Normal CO2. Decrease respiration to increase CO2 levels and lower the pH. Nothing and we don’t know why

Question 38

Mixed disorder- Respiratory acidosis and metabolic acidosis.

Answer 38

High CO2 and a low HCO3. Life threatening. The pH changes add together.

Question 39

Mixed disorder- Acidosis and alkalosis

Answer 39

They will cancel eachother out pH is subtractive. One will dominate but only slightly.

Question 40

Alcoholics Asthma COPD

Answer 40

Alcohol makes acid. But it will also make you vomit which causes alkalosis. This will give acidosis and alkalosis. Respiratory acidosis can’t remove CO2. Lack of oxygen causes anaerobic respiration which makes lactic acid. This gives two acidosis disorders. They are treated with diuretics which cause met alkalosis. And their lungs cause resp acidosis.