Problem:

Please read all the questions carefully and answer them.

Question 1: Arterial pH is typically near 7.4. This value can be predicted by the Henderson-Hasselbalch equation, which can be expressed as pH = 6.1 + log ([HCO3-] / [0.03 mmol L-1 mm Hg-1 x PCO2]. What does the value 6.1 represent?

(a) a constant,

(b) the pK for the bicarbonate/carbonic acid buffer system,

(c) the pH at which [HCO3-] and [H2CO3] are equivalent, or

(d) all of the above.

Question 2: Identify the metabolic end-products released by mitochondria:

(a) water,

(b) carbon dioxide,

(c) heat, or

(d) all of the above.

Question 3: Did the partial pressure of pulmonary carbon dioxide change during the case study?

(a) yes, or

(b) no.

Question 4: Pulmonary PCO2 is stabilized by an autonomic reflex that affects ventilation rate. Identify the location of the chemoreceptors that monitor bloodstream PCO2:

(a) lungs,

(b) pulmonary veins,

(c) heart chambers, or

(d) aortic arch and carotid body glomus organs.

Question 5: Is PCO2 measured within the CNS?

(a) no,

(b) yes, within the brainstem, or

(c) yes, throughout the brain.

Question 6: Is PO2 measured within the CNS?

(a) no,

(b) yes, within the brainstem, or

(c) yes, throughout the brain.

Question 7: Glomus organs are innervated by sensory neurons. How do these sensory neurons detect information output from chemoreptors within the glomus organ?

(a) ligand-gated sodium channels,

(b) voltage-gated sodium channels, or

(c) mechanically-gated sodium channels.

Question 8: Does the structure of a glomus organ enable the direct sampling of arterial blood?

(a) yes, or

(b) no.

Question 9: Axons that innervate glomus organs are myelinated and are found within two pairs of cranial nerves (glossopharyngeal and vagus). Which type of glial cell myelinates axons within nerves?

(a) oligodendrocyte,

(b) fibrous astrocyte, or

(c) Schwann cell.

Question 10: Upon entering the CNS, sensory neuron axons that project from glomus organs are bundled into left and right solitary tracts. However, where are the cell bodies of the sensory neurons to which these axons belong?

(a) glomus organs,

(b) a ganglion at the base of each nerve, or

(c) within the brainstem's solitary tract nuclei.

Question 11: The term hypercapnia denotes elevated bloodstream PCO2. This condition induces acidemia, i.e. an arterial pH < 7.4. By convention, the underlying physiological reason (or process) is called acidosis. Consequently, acidemia can arise from either metabolic acidosis (e.g. ketogenesis) or respiratory acidosis (hypoventilation). If arterial pH reaches 7.0, then CNS depression and coma follow. Acidemia is prevented by an autonomic reflex. Where does the central integration occur for this reflex?

(a) sensory cortex,

(b) brainstem, or

(c) spinal cord.

Question 12: Once again, pulmonary PCO2 is stabilized by an autonomic reflex that affects ventilation rate (volume of earth's atmosphere inhaled and exhaled per minute). Ventilation is best understood in terms of a pattern in which tidal volume and ventilation frequency - in proper combination - stabilize the gas profile within the lungs. This profile includes:

(a) oxygen,

(b) carbon dioxide,

(c) water vapor,

(d) nitrogen, or

(e) all of the above.