Q__________Post valentine Action potential=====q28 - miracoli - Printable Version +- USMLE Forum - Largest USMLE Community (https://www.usmleforum.com) +-- Forum: USMLE Forum (https://www.usmleforum.com/forumdisplay.php?fid=1) +--- Forum: Step 1 (https://www.usmleforum.com/forumdisplay.php?fid=2) +--- Thread: Q__________Post valentine Action potential=====q28 - miracoli (/showthread.php?tid=767598) |
Q__________Post valentine Action potential=====q28 - miracoli - ArchivalUser - 02-16-2014 A 55-yrs-old man sees a neurologist because of weakness in his legs that improves over the course of the day or with exercise. Extracellular electrical recordings from a single skeletal muscle fiber reveal normal miniature end-plate potentials. Low-frequency electrical stimulation of the motor neuron, however, elicits an abnormally small depolarization of the muscle fibers. The amplitude of the depolarization is increased after exercise.The molecular mechanism underlying these symptoms is most similar to which of the following? A) Acetylcholine B) Botulinum toxin C) Curare D) Neostigmine E) Tetrodotoxin 0 - ArchivalUser - 02-17-2014 E.. 0 - ArchivalUser - 02-18-2014 ?? 0 - ArchivalUser - 02-18-2014 BB Botulinum inhibits release AcCh. Tetrodotoxin acts by blocking Na channels. 0 - ArchivalUser - 02-18-2014 Botulinum toxin 0 - ArchivalUser - 02-18-2014 Yes it is B.. I overthought Like the molecular mechanism is channel blocking action and both the Ab and tetrodotoxin block the channel. But yes Botulinum is more sensible. 0 - ArchivalUser - 02-20-2014 BB is correct -Lambert-Eaton myasthenic syndrome(LEMS) and botulism cause Dysfunction in quantal Ca-mediated synaptic vesicle release mechanism to produce EPP but no effect on MEPP (because a synaptic vesicle can be releases SPONTANEOUSLY, without Calcium mediated, and produce MEPP) - Botulinum toxin inhibits muscle contraction presynaptically by decreasing the amount of ACh released into the neuromuscular junction. In contrast, curare acts post-synaptically, blocking the nicotinic ACh receptors and preventing the excitation of the muscle cell membrane. -Tetrodotoxin blocks voltage-sensitive Na+ channels, impacting both the initiation and the propagation of action potentials in the motor neuron. Both ACh and neostigmine stimulate muscle contraction. Thank you for participation For more explanation about membrane potential check here http://www.usmleforum.com/showthread.php?tid=767949 |