This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: DNB 2018, Subject name: Physiology
Peripheral chemoreceptors responds to hyproxia by oxygen sensitive: 
Select and explain. 
A. Na+ channel, B. Ca+2 channel, C. K+ channel, D. CI- channel
C: K+ channel
Answer: C: K+ channel 
Explanation: O2 levels are regulated almost entirely by peripheral chemoreceptors located in the carotid and aoic bodies; which in turn transmit appropriate signals to the respiratory center in the brain Carotid & aoic bodies have GLOMUS CELLS (multiple highly characteristic glandular - like cells) that synapse directly with nerve endings. Glomus cells have O2 sensitive K+ channels that are inactivated when blood Po2 decrease markedly. HYPOXIA O2 sensitive K+ channels inactivated. | Glomus cell depolarizes | Voltage gated Ca++ channel open, increase intracellular Ca++ | Neurotransmitter released, activates afferent neurons to CNS center of respiration.