Regulation of Respiration MCQs

The central chemoreceptors located on or near the ventral surface of the medulla cause an increase in ventilation in response to an increase in PacO2 and to a lesser extent to a decrease in arterial pH because the blood brain barrier is relatively impermeable to hydrogen ions. The peripheral chemoreceptors in the carotid bodies cause an increase in ventilation in response to an increase in PacO2 a decrease in arterial pH, and a decrease in PaO2. Neither the central chemoreceptors nor the carotid bodies are stimulated by a decrease in arterial blood pressure or O2 content.

J receptors were discovered by an Indian physiologist A. S. Paintal These receptors are located very close to the pulmonary capillaries (Juxta pulmonary receptors) in pulmonary interstitium Reference: Ganong, 25th edition page no.658

J receptors are activated by, Pulmonary congestion increases in the interstitial fluid volume of alveolar wall hyperinflation of the lung intravenous injection of chemicals like capsaicin So, J receptors are not a stimulus for normal respiration Reference: Ganong, 25th edition/page no.658

Because the deadspace air does not participate in gas exchange, the entire output of CO2 in the expired gas comes from the alveolar gas. Accordingly, CO2 output (VCO2) can be expressed in terms of alveolar ventilation ( VA ) and alveolar PCO2, according to the equation: PaCO2 = VCO2 / VA Because PaCO2 is essentially equal to PaCO2, this equation can also be expressed as PaCO2 = VCO2/ VA. Thus, an increase in alveolar ventilation at a constant rate of carbon dioxide production will lower the PaCO2 and PaCO2. Hyperventilation increases PaO2 and PaO2, with no change in the alveolar-arterial PaO2 difference. The V/Q would be normal or increased. Reference: Levitzky, pp 73-75.

At rest, expiration is a passive process Ventral VRG group of neurons controls forceful expiration. Reference: Ganong, 25th edition page no.655

Pre Botzinger complex is the pacemaker neuron for respiration They are seen in the ventral surfaces of medulla They are the first neurons to fire to generate respiratory rhythm Reference: Ganong, 25 th edition page no.655

Ans. is'd'i.e., AII of the above Central chemoreceptors - Ventral Surface Of Medulla. Peripheral chemoreceptors - At bifurcation of common carotid artery (carotid body) and arch of aorta (aortic bodies)

Peripheral chemoreceptors are more sensitive to hypoxia (reduced PO 2 ) Central chemoreceptors are more sensitive to hypercarbia (increased PCO 2 ) Central chemoreceptors are located in the floor of the fourth ventricle Reference: Ganong, 25th edition page no.658