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• Inside of the cell is
negative relative to the
outside of the cell.
• Electrical gradient
produces a membrane
potential (voltage) Resting Membrane Potential
• At equilibrium, inside of the cell
membrane would have a higher
[negative charges] than the outside.
• Potential difference: • Na is Not allowed in; K is K ontained. – Magnitude of difference in charge on
the 2 sides of the membrane.. • Depends upon 2 factors:
2 3 Cell Excitability (= Irritability)
• The ability to undergo rapid changes in
membrane potential in response to stimuli.
– Oocytes: rapid block to polyspermy.
– Neurons: conduct nerve impulses
– Muscle cells: initiate contraction – Ratio of the concentrations of each ion
on the 2 sides of the plasma membrane.
– Specific permeability of membrane to
each different ion. • Resting membrane potential of
most cells ranges from
- 65 to – 85 mV. Conduction of electrochemical
signals in neurons
• Nerves are NOT wires!
• Nerve impulses are
• Nerve impulse ar...
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- Fall '10