PHY2011 Lecture Notes - Lecture 7: Resting Potential, Membrane Potential, Depolarization
20 Jun 2018
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Week 3 L1 (T2L2) Resting Membrane potential and action potential
There’s a difference in charge across the membrane, even at resting
Action potential is the change in the resting potential
Change caused by a difference in distribution of ions
Selective permeability is responsible for change
The resting membrane potential (RMP)
oEM = -70mV
oThis means that the inside is 70mV more negative than outside
oTherefore, membrane is polarised
oIf EM becomes less negative (inside more positive) -membrane has depolarised
oIf EM becomes more negative (inside more negative) -membrane has hyperpolarised
Generating and maintaining the RMP
oSelectively-permeable membranes produce transmembrane potential difference(pd)
Allow the passage of only some ions (ie, positive ones, not negative ones)
Ions move with their concentration gradient; therefore, one side is more
positive and one more negative = potential difference
BUT once this happens, the negatively charged side will pull the positively
charged ions back (electrical gradient)
Equilibrium established: concentration and electrical gradients pulling ions
back at the same rate =equilibrium potential
- Exactly balances the force of the concentration gradient and
electrical gradient
- Calculated by the Nernst equation
- or (outside/inside)
- This equation shows the electrical gradient needed to balance it.
- For the inside to become negative, either a cation is leaving, or an
anion is entering or a bit of both
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Document Summary
Week 3 l1 (t2l2) resting membrane potential and action potential. There"s a difference in charge across the membrane, even at resting. Action potential is the change in the resting potential. Change caused by a difference in distribution of ions. Generating and maintaining the rmp: selectively-permeable membranes produce transmembrane potential difference(pd) Allow the passage of only some ions (ie, positive ones, not negative ones) Ions move with their concentration gradient; therefore, one side is more positive and one more negative = potential difference. But once this happens, the negatively charged side will pull the positively charged ions back (electrical gradient) Equilibrium established: concentration and electrical gradients pulling ions back at the same rate =equilibrium potential. Exactly balances the force of the concentration gradient and electrical gradient. This equation shows the electrical gradient needed to balance it. For the inside to become negative, either a cation is leaving, or an anion is entering or a bit of both.
