Snapshot A 24-year-old patient presents with rapid onset dizziness, nausea, and weakness at a restaurant in Japan. Prior to this presentation, it was disclosed to the paramedics that he had been eating a Japanese delicacy. (Tetrodotoxin poisoining from consumption of pufferfish) Overview Action Potential Action potential resting membrane potential (-70 mV) determined by permeability to potassium (K+), sodium (Na+), and chloride (Cl-) roughly -70 mV, with the greatest permeability being to K+ threshold (approximately -55 mV) neuron must receive enough stimulus to reach threshold login to view 3 more bullets depolarization (+50 mV) once threshold is met, voltage-gated Na+ channels open login to view 5 more bullets pathophysiology correlate login to view 3 more bullets hyperpolarization at the peak membrane voltage (+50 mV), voltage-gated Na+ channels close and delayed outward-rectifier K+ channels open login to view 2 more bullets baseline eventually the K+ channels return to their baseline state and the membrane potential reaches -70 mV again until another stimulus surpasses threshhold NOTE: the ion gradients are continually reestablished by the activity of the Na+/K+ ATPase which pumps 3 Na+ out of the cell for every 2 K+ transported in