During an acute apneic event, which receptors respond to increases in PaCO2?

During an acute apneic event, central chemoreceptors play a critical role in responding to increases in arterial carbon dioxide tension (PaCO2). These receptors are located in the medulla oblongata of the brain and are highly sensitive to changes in the pH of the cerebrospinal fluid, which is influenced by the levels of carbon dioxide in the blood.

When there is an increase in PaCO2, it leads to a rise in carbonic acid in the blood, which subsequently lowers pH. The central chemoreceptors detect this change and stimulate the respiratory centers in the brain to increase the rate and depth of breathing to expel the excess carbon dioxide and restore normal gas levels. This response is crucial during an apneic event, where automatic breathing is temporarily halted, as it helps to quickly resume normal respiratory function.

In contrast, peripheral chemoreceptors primarily respond to changes in oxygen levels (PaO2) and are less involved in immediate responses to increased PaCO2 during acute events. Baroreceptors are involved with blood pressure regulation, and mechanoreceptors are connected to detecting stretch in the lungs and airways, which do not have a direct role in the acute regulation of CO2 levels. Thus, the central che