<prompt> d-Tubocurarine -Mechanism of action:Competitive, nondepolarizing block at the Nm cholinergic receptorsNoncompetitive, nondepolarizing block at the Nm cholinergic receptorsCompetitive, depolarizing block at the Nm cholinergic receptorsNoncompetitive, Depolarizing block at the Nm cholinergic receptors  <response>: Ref. KDT. Page. 352d-TCThe competitive blockers have affinity for the nicotinic NM cholinergic receptors at the muscle end plate, but have no intrinsic activityMost of the competitive blockers have two or more quaternary N atoms which provide the necessary attraction to the same site, but the bulk of the antagonist molecule does not allow conformational changes in the subunits needed for opening the channeld-TC thus reduces the frequency of channel opening but not its duration or the conductance of a channel once it has opened.The competitive blockers also block prejunc- tional nicotinic receptors located on motor nerve endings 