Physiology 1

Question 1

Normal aortic pressures?

Answer 1

120/80 mmHg

Question 2

Normal LV pressures?

Answer 2

121/0 mmHg

Question 3

Normal LA pressures?

Answer 3

8-10 mmHg

Question 4

Normal RV pressures?

Answer 4

25/0 mmHg

Question 5

Normal RA pressures?

Answer 5

0-4 mmHg

Question 6

Physiological hydrogen ion concentration? (ie. pH 7.4)

Answer 6

40 nM/L

Question 7

Usual pH of gastric juices?

Answer 7

pH 1-3

Question 8

Usual pH of Urine?

Answer 8

pH 5-6

Question 9

Usual pH of arterial blood?

Answer 9

pH 7.38-7.42

Question 10

Usual pH of venous blood?

Answer 10

pH 7.37

Question 11

Usual pH of CSF?

Answer 11

pH 7.32

Question 12

Usual pH of pancreatic fluid?

Answer 12

pH 7.8-8.0

Question 13

Why is tight pH control important for physiological function?

Answer 13

1. Needed for normal fuctioning of mitochondrial proton pump and thus oxidative phosphorylation and production of ATP
2. Needed to maintain structural integrity and function of enzymes and proteins.
3. Affects HbO2 dissociation curve.
4. Affects ionic flux

Question 14

H+ concentration at pH 7.0?

Answer 14

100 nM/L

Question 15

Approx how many moles of CO2 is produced daily by metabolism?

Answer 15

13-15 mol

Question 16

Approx how many moles of fixed acids is produced daily by muscle protein metabolism?

Answer 16

50-80 mmol

Question 17

Which systems act as a defence against acidaemia?

Answer 17

1. Buffers (rapid, seconds)
2. Respiratory (fast, minutes)
3. Renal (slower, hours)
4. Hepatic (slower, hours)

Question 18

pK of HCO3?

Answer 18

pK 6.1

Question 19

pK of Hb? (histidine)

Answer 19

pK 7.8

Question 20

pK of amino- and carboxyl- proteins?

Answer 20

pK 7.4

Question 21

pK of PO4?

Answer 21

pK 6.8

Question 22

What is the Henderson-Hasselbalch equation?

Answer 22

pH = pK + Log10 [A-] / [HA]

Question 23

What are the main physiological buffer systems?

Answer 23

1. Bicarbonate
2. Phosphate
3. Proteins
4. Carbonate

Question 24

Where is the main site of action of phosphate as a buffer?

Answer 24

Renal tubules

Question 25

Most significant contributor to intracellular buffering?

Answer 25

Hb (histidine residues) | 75% of all intracellular buffering

Question 26

Location of CO2 chemoreceptors?

Answer 26

Medulla and carotid bodies

Question 27

Define control effectiveness

Answer 27

The ability (or efficiency) of a homeostatic mechanism to resist a change in the parameter it controls. eg. lungs have 50-75% control effectiveness and therefore will compensate 5-7.5 nmol of a 10 nmol change in [H+]

Question 28

Through which mechanisms do the kidneys affect acid base balance?

Answer 28

1. H+ secretion 2. HCO3- filtration 3. HCO3- generation

Question 29

Where and how is H+ secreted in the kidneys?

Answer 29

Collecting tubules | Via primary and secondary active transport

Question 30

What are the three main urinary buffers?

Answer 30

Bicarb Phosphate Ammonia

Question 31

How does the liver contribute to acid-base balance?

Answer 31

1. CO2 production 2. Metabolism of organic acid anions 3. Production of plasma proteins 4. Metabolism of ammonium 5. Ureagenesis

Question 32

Summarise ureagenesis

Answer 32

Amino acid metabolism -> HCO3- and NH4+ 2NH4+ + 2HCO3- -> Urea + CO2 + 3H2O

Question 33

Chemical structure of urea?

Answer 33

NH2CONH2

Question 34

What are the products of anaerobic metabolism?

Answer 34

ATP Lactate Water

Question 35

What is the definition of hyperlactataemia?

Answer 35

>2 mmol/L

Question 36

Definition of lactic acidosis?

Answer 36

>5 mmol/L and pH <7.35

Question 37

What is the normal lactate:pyruvate ratio?

Answer 37

10:1

Question 38

What does a lactate:pyruvate ratio of >10:1 indicate?

Answer 38

Tissue hypoxia

Question 39

Anion gap calculation?

Answer 39

([Na] + [K]) - ([Cl] + [HCO3])

Question 40

Causes of high anion gap acidosis?

Answer 40

CATMUDPILES ``` C: CO, CN A: Alcoholic/starvation ketoacidosis T: Toluene M: Methanol, Metformin U: Uraemia D: DKA P: Pyroglutamic acidosis, paracetamol, phenformin, propylene glycol, paraldehyde I: Isoniazid, Iron L: Lactate E: Ethylene glycol S: Salicylates ```

Question 41

Causes of normal anion gap acidosis? (aka. Hyperchloraemic acidosis)

Answer 41

CRAG (chin-rubbing anion gap) C: Chloride excess R: Renal tubular acidosis A: Addison's, Acetazolamide, Ammonium G: GI losses of bicarb

Question 42

Causes of low anion gap?

Answer 42

V rare. HP BLIP H: Hypoalbuminaemia (most common) P: Paraproteins B: Bromide L: Lithium I: Iodine P: Polymyxin B (antibiotic)

Question 43

What does standard bicarb measure?

Answer 43

Bicarb corrected to normal temp and CO2 level

Question 44

Define base excess

Answer 44

The amount of acid or base required to bring a sample of blood to pH 7.4 in presence of normal PaCO2 (5.33 kPa)

Question 45

Compare and contrast the alpha-stat and pH-stat approaches to pH management

Answer 45

Refer to management of the hypothermic patient Alpha-stat postulates that due to the constant buffering effect of imidazole/histidine intracellularly at low temperatures, intracellular pH is maintained and therefore does not need to be corrected. pH-stat approach suggests that the Rosenthal correction factor should be used to alter parameters, advocating respiratory acidosis to maintain a 'normal' pH. No clear evidence exists for the advantage of one over the other.

Question 46

How does ureteric transplant cause acidosis?

Answer 46

Urinary chloride is exchanged for HCO3 in the colon, causing hyperchloraemic acidosis.

Question 47

Outline Stewart's acid-base theory

Answer 47

Dependent variables produce effects (through water dissociation): H+ pH HCO3- Independent variables act as controllers: PCO2 Net strong ion charge (SID) Total weak acid

Question 48

What is a normal strong ion difference?

Answer 48

40-42 mEq/L

Question 49

What are the 'strong ions'?

Answer 49

Na, K, Ca, Mg, Cl, Lactate

Question 50

According to Stewart's Theory, what happens with an increase in SID?

Answer 50

pH will increase (alkalosis)