Hypercapnia affects respiration primarily by stimulating the

The correct answer is Central medullary chemoreceptors

Concept:

• Hypercapnia refers to an elevated level of carbon dioxide (CO₂) in the blood, which can significantly affect respiration.
• The body has specialized mechanisms to sense changes in CO₂ levels and maintain homeostasis, primarily through respiratory control centers in the brainstem.
• The central medullary chemoreceptors, located in the medulla oblongata of the brainstem, play a pivotal role in detecting increases in CO₂ levels (hypercapnia) and initiating appropriate respiratory responses.

Explanation:

• Central medullary chemoreceptors located near the medulla, are sensitive to changes in the pH of the cerebrospinal fluid (CSF), which is influenced by CO₂ levels in the blood.
  • When CO₂ levels rise, it diffuses into the CSF and forms carbonic acid, lowering the pH.
  • The chemoreceptors detect this change and stimulate the respiratory centers to increase the rate and depth of breathing, helping to expel excess CO₂.
  • This is the primary mechanism through which hypercapnia affects respiration, making it the correct answer.

Other Options:

• Carotid and aortic bodies: These are peripheral chemoreceptors located in the carotid arteries and aortic arch, respectively. While they are sensitive to changes in blood oxygen (O₂) levels, they also respond to CO₂ and pH changes to some extent. However, their response to hypercapnia is secondary compared to the central medullary chemoreceptors.
• Hypoglossal nerve: This cranial nerve primarily controls the muscles of the tongue and does not play a direct role in detecting or responding to hypercapnia.
• Arterial baroreceptors: These receptors are located in the carotid sinus and aortic arch and are primarily involved in detecting changes in blood pressure, not CO₂ levels.