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Neuronal Membrane
- Made up on phospholipid bilayer
- Prevents most substances from freely passing
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5 Ions that Surround Membrane
- Cations(positively charged):
- Sodium (NA+)
- Potassium (K+)
- Calcium (Ca2+)
- Anions (negatively charged):
- Chloride (Cl-)
- Negatively charged proteins (A-)
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Distribution of ions across the neuronal membrane
- Outside:
- Sodium
- Chloride
- Calcium
- Inside:
- Potassium
- Negatively charged proteins
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Ion Movement
K+ and Cl- __________
Na+ and Ca2+ do ____________
A- proteins ARE ___________
- K+ and Cl- PASS FREELY
- Na+ and Ca2+ do NOT PASS EASILY
- A- proteins ARE IMPERMEABLE
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Diffusion
Spontaneous spread of molecules until a uniform concentration is achieved
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Electrostatic pressure
Propensity of charged molecules or ions to move, via diffusion, toward areas with the opposite charge
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Intracelluar microelectrode:
A conductive medium that can be used to ___________________ or _________ electrical potentials.
A conductive medium that can be used to apply electrical current or record electrical potentials.
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Resting membrane potential (-60 mV)
Neuron is more negative inside relative to outside of cell
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Sodium-potassium pump
- excludes 3 Na+ ions for every 2 K+ ions taken into the cell
- Requires energy supplied by ATP, which is converted to ADP
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What happens if you allow Sodium to pass easily?
- Sodium rushes into the cell
- Not at resting potential
- Insert channels and Sodium
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Equilibrium potential
- Potential at which force of diffusion is balanced by the force of electrostatic pressure
- no net movement of the ion
- K+ has equilibrium potential of -90 mV
- Na+ has equilibrium potential of +55 mV
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The resting membrane potential can be simply altered by
simply changing the permeability of the membrane
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