Test 21 (general physiology)

1. Red blood cells:

a. measured 15 um in diameter

b. do not contain mitochondria

c. have a life span of 120 days in the circulation

d. are released from the bone marrow as mature erythrocytes

e. express HLA class II antigens on the cell surface

answera.F   b.T   c.T   d.F   e.F
The normal red blood cells measured 8 um in diameter.
Newly formed red blood cells (reticulocytes) remain in the bone marrow for 2-3 days before being released into the circulation. 
Mature red blood cells do not contain mitochondria or ribosomes.
HLA class II antigens are expressed only on the surface of  B cells, activated T cells, macrophages and damaged endothelium.

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2. The following are true about the ABO and rhesus (Rh) system:

a. a person of group O is a universal donor

b. a person who is group AB has anti-A and anti-B antibodies

c. the presence of the D antigen means that the subject is Rh positive

d. rhesus antibodies occur naturally

e. the second rhesus positive baby of a Rh negative mother is at a greater risk 
    than the first

answera.T   b.F   c.T   d.F   e.T
A person with group AB means that he has no anti-A or anti-B antibodies. 
Rhesus antibodies occur in response to exposure to the D antigen.
Previous sensitization means that the second baby is more at risk that the first.
 

3. The oxygen dissociation curve is shifted to the right with:

a. polycythaemia

b. pyrexia

c. respiratory acidosis

d. sickle cell anaemia

e. decreased concentration of 2,3-DPG in the erythrocytes.

answera.F   b.T   c.T   d.T   e.F
The oxygen dissociation curve is shifted to the right by a higher pCO₂, increased temperature, acidosis and 2,3-DPG (2,3-diphosphoglycerate).
2,3-DPG production is increased by anaemia.

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4. The intracranial pressure is decreased by:

a. intravenous mannitol

b. placing the patient in a head-up position

c. hyperventilation

d. a rise in the arterial pCO₂

e. the administration of sodium nitroprusside

answera.T   b.T   c.T   d.F   e.T
Hyperventilation reduces the arterial pCO₂ which in turn leads to vasoconstriction and therefore lower pCO₂. Sodium nitroprusside reduces the arterial blood pressure and therefore decreases the intracranial pressure.

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5. Dilatation of the peripheral arterial blood vessels can be caused by:

a. thromboxane A₂

b. adenosine diphosphate

c. endothelin

d. prostaglandins

e. nitric oxide.

answera.F   b.F   c.F   d.T   e.T
Vasodilatation can be caused by prostaglandins and nitric oxide (NO).
NO is synthesized from L-arganine in vessel walls by NO synthases.
Endothelin is produced by endothelial cells and by neurones in the paraventricular nucleus of the hypothalamus.
Vasodilatation also occurs in increased local temperature, increased pCO₂, lactic acid, histamine and decreased sympathetic activity.