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The Resting Membrane Potential

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Move from area of high concentration to areas of low concentration ... Z = valence (charge) of ion ~ Equilibrium Potential. Constants never change. Assume 25 oC ... – PowerPoint PPT presentation

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Title: The Resting Membrane Potential


1
The Resting Membrane Potential
  • Lecture 4

2
Biolelectric Potential
  • Communication within neuron
  • electrical signal
  • electric current movement of electrons
  • Bioelectric movement of ions

3
Ion Distribution
  • Particles / molecules
  • electrically charged
  • Anions
  • negatively charged
  • Cations
  • positively charged

4
Ion Distribution
  • Anions (-)
  • Large intracellular proteins
  • Chloride ions Cl-
  • Cations ()
  • Sodium Na
  • Potassium K

5
Resting Membrane Potential
  • Na Cl-
  • A- K

outside
Membrane
inside
6
Membrane is polarized
  • more negative particles in than out
  • Bioelectric Potential
  • like a battery
  • Potential for ion movement
  • current

7
Resting Membrane Potential
outside











Membrane
-
-
-
-
-
-
-
-
-
-
-
inside
8
Bioelectric Potential
OUTSIDE
INSIDE
9
Forces That Move Ions
10
Gradients
  • Concentration (C)
  • Electrostatic (E)

11
Concentration gradient
  • Movement of particles in fluid
  • Move from area of high concentration to areas of
    low concentration
  • Diffusion
  • Random movement of particles

12
Concentration gradient
Lo
HI
13
Concentration gradient
Lo
HI
14
Electrostatic gradient
  • Ions charged particles
  • Like charges repel
  • Opposite charges attract

15
Electrostatic gradient
like charges repel
16
Electrostatic gradient
opposite
charges attract
17
Equilibrium Potential
  • Also called reversal potential
  • Distribution of single ion across membrane
  • e.g., EK, ENa, ECl-
  • Potential for movement of ion if channel opens
  • units millivolts (mV)
  • outside 0, by convention

18
Equilibrium Potential
  • R gas constant
  • F Faraday constant
  • T temperature (K)
  • Z valence (charge) of ion

19
Equilibrium Potential
  • Constants never change
  • Assume 25 oC
  • Use log10

20
Equilibrium Potential
21
Membrane Potential
  • Net bioelectric potential
  • for all ions
  • Balance of both gradients
  • concentration electrostatic
  • Units millivolts (mV)
  • Vm -65 Mv
  • given by Goldman equation

22
Membrane Potential Goldman Equation
  • P permeability
  • Net potential movement for all ions
  • known VmCan predict direction of movement of any
    ion

23
Organic anions - Membrane impermeable Opposing
electrical force not required

Vm -65 mV
A-
24
Chloride ion
Cl-
Vm -65 mV
  • Concentration gradient equal to electrostatic
    gradient.
  • Leaks out neuron
  • ECl- - 65 mV

25
Potassium ion
Vm -65 mV
K
  • Concentration gradient greater than electrostatic
    gradient.
  • Leaks out neuron
  • EK - 75 mV

26
Na
Sodium ion
C
Vm -65 mV
  • Concentration gradient and electrostatic gradient
    into neuron.
  • ENa 55 mV

27
Metabolic Pumps
  • Active Transport mechanisms
  • Require energy
  • Move materials against gradient
  • Na - K
  • Calcium - Ca
  • Nutrients, etc.

28
Na - K Pump
  • Maintains gradients at rest
  • Pumps 3 Na out of cell
  • 2 K into cell
  • Energy ATP

29
Inside
Outside
Na
Na
Na
K
K
30
Inside
Outside
K
K
K
K
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