The resting membrane potential of a typical neuron is –60 to ...
Understanding Resting Membrane Potential
The resting membrane potential of a neuron typically ranges from -60 to -80 millivolts (mV). This potential is primarily determined by the distribution and permeability of different ions, particularly potassium (K+) and sodium (Na+).
Key Factors Influencing Resting Membrane Potential
- Non-gated K+ Channels
Neurons possess a significant number of non-gated (leak) potassium channels. These channels allow K+ ions to flow out of the cell down their concentration gradient. The high permeability to K+ due to these channels plays a crucial role in establishing a negative membrane potential.
- Limited Non-gated Na+ Channels
In contrast, there are very few non-gated sodium channels in the resting state. This means that Na+ cannot enter the cell as freely as K+ can exit. Thus, the inward movement of Na+ is minimal, which helps maintain a negative charge inside the neuron.
Comparative Ion Movement
- K+ Movement
K+ ions move out of the neuron, which contributes to a more negative interior. This outward diffusion of K+ is a primary factor in achieving the resting potential.
- Na+ Movement
While Na+ does have a concentration gradient that drives it into the cell, the limited number of non-gated Na+ channels restricts its influx during the resting state. Thus, Na+ does not significantly counteract the negative charge created by K+ efflux.
Role of Na+/K+ Pump
- The Na+/K+ pump actively transports three Na+ ions out of the cell and two K+ ions into the cell, contributing to the overall ion balance. However, its role is more about maintaining the gradients rather than directly establishing the resting potential.
In summary, the resting membrane potential is primarily due to the high permeability of the neuronal membrane to K+ ions, facilitated by numerous non-gated K+ channels.
The resting membrane potential of a typical neuron is –60 to ...
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