Test 155  (General physiology)

1. Urine volume is increased with:

a. carbonic anhydrase inhibitors

b. hyperglycaemia

c. increased aldosterone secretion

d. damage to the posterior pituitary

e. consumption of alcohol
 

Answera.T   b.T   c.F    d.T   e.T
Carbonic anhydrase inhibitors increase the secretion
of sodium and potassium ions and hence diuresis. 
Hyperglycaemia causes glycosuria and acts as an 
osmotic diuretic. ADH is decreased with posterior 
pituitary gland. Alcohol inhibits ADH production 
and hence results in diuresis. Aldosterone increases the reabsorption of sodium and reduces urine output. 
 

2. With regard to the transport of carbon dioxide in blood:

a. 25% of carbon dioxide is dissolved in blood

b. carbonic anhydrase is found in plasma

c. 50% of carbon dioxide is carried as bicarbonate

d. deoxygenated haemoglobin facilitates the transport of
    carbon dioxide

e. carbamino compounds are formed from the reaction 
    between carbon dioxide reacts with haemoglobin
 

Answera.F   b.F  c.F  d.T  e.T
Carbonic anhydrase is found in the red blood cells
and not in the plasma. 5% of carbon dioxide is dissolved in plasma, 5% as carbamino compounds and the majority ie. 90% is carried as bicarbonate. Carbamino compounds are formed more readily 
in deoxygenated haemoglobin and therefore venous 
blood is more efficient than the arterial blood in transporting carbon dioxide.
 

3. The following are true about cerebrospinal fluid:

a. it has a greater buffering capacity than plasma

b. it has a similar chloride concentration to plasma

c. it is a plasma ultrafiltrate

d. the rate of formation is dependent on the intraventricular
    pressure over the normal pressure range 

e. its main function is to act as a cushion to protect the 
    brain
 

Answer
a.F   b.F   c.T   d.F  e.T
Its buffering capacity is less than plasma because it has less protein content. The chloride concentration is higher than that of plasma. The rate of formation is independent of the intraventricular pressure until the pressure is above the normal range. However, the orate of absorption is dependent on the pressure.
 

4. True statements about the pH of the extracellular fluid:

a. in healthy people it is maintained between 7.4 and 7.5

b. is increased in hypovolaemic shock

c. decreases following a cardiac arrest

d. influences the binding of drugs to plasma proteins

e. the lungs and the kidneys play an important in the 
    regulation of plasma pH

Answer
a.F   b.F  c.T  d.T  e.T
The normal pH is maintained between 7.35 and 7.42. The pH is maintained by several buffering systems 
including the bicarbonate/carbonic system, phosphate 
system and serum proteins and haemoglobin. Kidneys 
and the lungs also play an important role. With 
hypovolaemic shock, the tissue perfusion is low leading to a decrease in pH.

 

5. The following occur in the proximal tubules of the nephron:

a. reabsorption of all glucose

b. reabsorption of most water

c. secretion of bicarbonate

d. active reabsorption of sodium

e. action of aldosterone resulting in sodium reabsorption.
 

Answer
a.T   b.T  c.F   d.T  e.F
70% of water is reabsorbed in the proximal tubule. Bicarbonate, chloride and sodium are reabsorbed here. Aldosterone acts on the distal tubules.

 

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