<prompt> Which one the following does NOT primarily involve an action K channels?Hypoxic Pulmonary VasoconstrictionInsulin secretion by SulfonylureaCarotid body discharge with reduced O2Dantrolene in the treatment of Malignant Hypehermia  <response>: Hypoxic pulmonary vasoconstriction and carotid body discharge are brought about by the O2-sensitive K channel. Insulin secretion by sulfonylurea is brought about by its action the ATP-sensitive K channel on the pancreatic b-cell. Malignant hypehermia is a disorder of excitation-contraction coupling, resulting from genetic defect of RyR a Ca-release channel. Dantrolene uncouples the excitation from contraction, by acting on the Ca channel. 