The feedback mechanisms for the control of breathing are mos

The feedback mechanisms for the control of breathing are most sensitive to:

a) decreased concentration of oxygen in the atmosphere.

b) mechanical receptors in the thoracic musculature.

c) changes in blood PCO2.

d) blood pressure changes in the carotid sinus.

e) changes in blood pH.

Solution

The master controller centre in the brain for control of breathing is medulla oblongata of the hind brain. This region contains nerve endings which are directly related to afferent neurons of the carotid sinus in the heart. This carotid sinus is highly sensitive to changes in partial pressure of CO2 in the arterial/oxygenated blood. Unlike other beliefs, the carotid artery senses the concentration of dissolved CO2 and not O2 in the blood coming directly from lungs as a result of ventilation and gaseous exchange across the pulmonary bed. Thus, decrease or dampened ventilation and breathing will result in enhanced partial pressure of CO2 in arterial blood which is directly sensed by the carotid sinus. The carotid sinus then sends signal to the medulla centre which activates and promotes upregulation of breathing.

Thus, owing to this information, the correct answer is choice C.