CRL Quiz 2 Sample 2

1

Which one of the following statements regarding pneumonia is NOT CORRECT?


  The work of breathing is increased because pneumonia is an inflammatory disorder causing obstruction of the alveolar spaces.

  Gas exchange is abnormal because of ventilation – perfusion mismatch and sometimes shunt.

  The common causes of pneumonia in previously well adults include bacteria, viruses, fungi and worms.

  Severe pneumonia can result in an acidosis due to respiratory and metabolic factors.


A is correct: Pneumonia involves the terminal lung units (ie small airways, alveolar spaces +/- interstitial spaces).
B is correct: There may also be diffusion impairment, but this is less of a problem at rest.
C is not correct: Strepococcus pneumoniae and (in younger adults) Mycoplasma pneumoniae and Chlamydia pneumoniae are the common causes of community – acquired pneumonia in previously well adults (Legionella can be important in outbreaks). Viral pneumonia is rare (except in influenza or SARS epidemics). Fungal, protozoal and worm lung infections are very rare in the immunocompetent.
D is correct: Poor tissue oxygenation due to a very low PaO2 can cause a metabolic acidosis and an elevated PaCO2 due to severe pneumonia will cause a respiratory acidosis.

2

Which one of the following statements regarding the regulation of heart rate is correct?


  β-adrenoceptor antagonists prevent the effects of activation of cardiac parasympathetic nerves.

  Stimulation of cardiac parasympathetic nerves increases heart rate.

  In a healthy human at rest there is no influence of sympathetic nerves on heart rate.

  Muscarinic receptor antagonists increase resting heart rate.


A is incorrect: Stimulation of cardiac parasympathetic nerves decreases heart rate due to the release of acetylcholine which activates muscarinic receptors.
B is incorrect: Acetylcholine released from parasympathetic nerves acts on muscarinic receptors to decrease heart rate.
C is incorrect: At rest there is low level of tonic activity of the cardiac sympathetic nerves to increase heart rate.
D is correct: At rest there is significant tonic activity of the cardiac parasympathetic nerves to keep heart rate low. Muscarinic receptor antagonists will prevent that effect and allow heart rate to increase.

3

Antigen presentation to T cells on first exposure to an inhaled foreign antigen usually occurs in which one of the following sites?


  The lung epithelium.

  Lymph nodes draining the lung.

  Germinal centres in the airway mucosa.

  Bronchus associated lymphoid tissue.

  Blood in the airway microcirculation.

4

Which one of the following statements regarding the valves of the heart is correct?


  The aortic valve is open during ventricular diastole.

  The edges of the atroventricular valve cusps are attached directly to the papillary muscles which prevent eversion during ventricular systole.

  The aortic and pulmonary valves are composed of 3 semilunar cusps attached at their bases to the vessel wall.

  The mitral (bicuspid) valve is closed during ventricular systole preventing regurgitation of blood from the right ventricle to the right atrium.


A is incorrect: The aortic valve is closed during ventricular diastole.
B is incorrect: The edges of the valve cusps are attached to chordae tendinae which in turn are attached to the papillary muscles.
D is incorrect. The mitral valve guards the passage of blood between the left ventricle and the left atrium.