MATH 246 Midterm: Practice Exam 1 Solutions Fall 2008
14 Mar 2019
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The key here is a simple transformation if you start at -70 mv and end at -60 mv, -60. 5 mv is 95% of the final depolarization. You were told 1 is 0. 1 milliseconds and so 3. This question was meant to see if you understood the same that determines rise of membrane potential when you add current also governs the decline in membrane potential when you shut off that current. Again, in going 10 mv from one membrane potential (-60 mv) to resting membrane potential (-70 mv) you will have to wait a time equivalent to 3 to get 95% of the way. Since 0. 5 mv is 95% of 10 mv, it will take 3 or 0. 3 milliseconds to get back to -69. 5 mv (a depolarization of at least 0. 5 mv). Add 0. 3 milliseconds to the time the channels stay open in the first place (0. 3 milliseconds) and you have the final answer of.
