This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Excitation and Action Potiential, Subject name: Physiology
[{'content': 'If this cell were permeable only to K+, what would be the effect of reducing the extracellular K concentration from 5 to 2.5 millimolar? Intracellular (mM) Extracellular (mM) 140 K+ 5 K+ 12 Na+ 145 Na+ 5 CI- 125 CI- 0.0001 Ca++ 5 Ca++ \nSelect and explain. \nA. 19 millivolts depolarization, B. 19 millivolts hyperpolarization, C. 38 millivolts depolarization, D. 38 millivolts hyperpolarization', 'role': 'user'}, {'content': 'Answer: B \nExplanation: If a membrane is permeable to only a single ion Vm is equal to the equilibrium potential for that ion. In this hypothetical cell, EK+ = 88 millivolts. If the extracellular K+ concentration is reduced by half, EK+ = 61 x log (2.5/140) = 107 millivolts, (Hyperpolarisation of 19 millivolts.)', 'role': 'assistant'}]