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Factors That Determine the Resting Membrane Potential

  • The plasma membranes of resting axons are slightly polarized due to the unequal distribution of Na+, K+, Cl- and protein- ions in ECF and ICF.
  • Several factors play a role in creating the resting membrane potential.
  • image descriptionNa+/K+ pumps (or Na+/K+-ATPases) move Na+ and K+ ions to opposite sides of the membrane.
An image showing different types of channels in the (neuron) cell membrane (between ICF and ECF)
An image showing different types of channels (Na-K pump is labeled) in the (neuron) cell membrane (between ICF and ECF)
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  • Each pump protein uses one molecule of ATP to image descriptiontransfer 3 Na+ ions out of the cell and 2 K+ ions in.
  • As a result, Na+ ions are concentrated outside the axon membrane and K+ ions are concentrated inside. The unequal transfer of ions also contributes slightly to the polarity of the resting membrane.
  • Very few of the Na+ ions can diffuse back into the cell because most of the gated image descriptionNa+ channels are closed.
An image showing different types of channels (Na-K pump is labeled) in the (neuron) cell membrane (between ICF and ECF)
An image showing different types of channels (Na channel - Na-K pump are labeled) in the (neuron) cell membrane (between ICF and ECF)
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An image showing different types of channels (Na channel - Na-K pump are labeled) in the (neuron) cell membrane (between ICF and ECF)
An image showing different types of channels (K channel - Na channel - Na-K pump are labeled) in the (neuron) cell membrane (between ICF and ECF)
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  • However, many image descriptionleak channels remain open, which increases the membrane’s permeability to K+ ions.
An image showing different types of channels (K channel - Na channel - Na-K pump are labeled) in the (neuron) cell membrane (between ICF and ECF)
An image showing different types of channels (K leak channel - K channel - Na channel - Na-K pump are labeled) in the (neuron) cell membrane (between ICF and ECF)
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  • As K+ ions image descriptiondiffuse outward, the interior of the membrane becomes more negative and the exterior more positive, which significantly alters the RMP.
  • Proteins- and other large anions confined within cell also contribute to the membrane’s polarity.
  • An image descriptionequlibrium is quickly reached be-tween the outward diffusion gradient for K+ and the inward electrical gradient.
An image showing different types of channels (K leak channel - K channel - Na channel - Na-K pump are labeled) in the (neuron) cell membrane (between ICF and ECF)
An image showing different types of channels equilibrium status of K leak channel in addition to (K channel - Na channel - Na-K pump are labeled) in the (neuron) cell membrane (between ICF and ECF)
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  • As the RMP stabilizes, Cl- ions passively disperse based on the permeability and polarity of the plasma membrane. Becasue the ICF is relatively negative, Cl- ions are repelled and tend to concentrate outside of the membrane.