University:
University of California, Berkeley
Course:
PHYSICS 89 | Introduction to Mathematical Physics
Academic year:

2021
Views:

249

Pages:

2
Author:

blakestar2o1o

ACTION POTENTIAL!! Worksheet For the following problems, assume you are recording from a “typical” neuron with a resting potential of -70 mV and injecting current into it. Remember as you work the given equilibrium potential for K+ and Na+, and the role of K+ in establishing the resting potential. 1. Draw the “typical” action potential, label the following on the graph. (NOTE: this one is very clunky, so feel free to skip it) a) resting potential (our baseline for the cell being “polarized”) b) small depolarization that reaches threshold c) Depolarization and reversal of membrane potential d) Re-reversal and re-polarization toward baseline e) Hyperpolarization f) Return to resting potential again 2. Draw the “typical” action potential, label the following on the graph. a) opening of v-gated Na+ channels b) opening of v-gated K+ channels (delayed rectifier) c) inactivation of v-gated Na+ channels d) resetting of v-gated Na+ channels e) closing of v-gated K+ channels How do we know that Na+ drives the rising phase of the action potential? 3. To answer this question let’s do an experiment where we reduce the extracellular Na+ concentration. Assume we have now made the extracellular concentration of Na+ equal to the intracellular concentration of Na+. Draw the action potential that would result with this concentration difference. 4. To further explore this question, let’s consider the role of v-gated Na+ channels. Tetrodotoxin (TTX) acts as a v-gated Na+ channel blocker. Draw the action potential that would result from stimulation of the membrane to threshold potential when TTX is added to the extracellular fluid. What is the role of K+ in the action potential? 5. To answer this question, let’s consider the role of v-gated K+ channels. Tetraethylammonium (TEA) acts as a v-gated K+ channel blocker; Add TEA to the extracellular fluid and then draw the action potential. 6. To further explore this question, let’s do an experiment where we increase the extracellular concentration of K+. Assume we have now made the extracellular concentration of K+ equal to the intracellular concentration of K+. Draw your best approximation of the action potential that would result with this concentration difference. Final questions to think about: 1. What causes Na+ channels to open? 2. What causes Na+ channels to inactivate? 3. What causes Na+ channels to reset back to the closed state (but no longer inactivated)? 4. What causes K+ channels to open? 5. What causes K+ channels to close? 1. 2. 1. 3. 4. 5. 6.