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This ion is primarily responsible for maintaining the resting membrane potential of excitable cells.

User PeteLe
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Final answer:

The potassium ion (K+) is primarily responsible for maintaining the resting membrane potential in excitable cells, with the sodium-potassium pump further contributing to the maintenance of this potential by actively transporting ions across the cell membrane.

Step-by-step explanation:

The ion that is primarily responsible for maintaining the resting membrane potential of excitable cells is the potassium ion (K+). Potassium is the major intracellular cation, with a high concentration inside the cell compared to the outside.

This disparity in concentration, along with selective membrane permeability that favors potassium movement out of the cell, establishes a negative charge inside the cell relative to the extracellular fluid.

The actions of the sodium-potassium pump are vital for maintaining this potential over the long term. This pump uses ATP to move two K+ ions into the cell and three Na+ ions out.

This movement contributes to the negative charge inside the neuron since more positive charges are expelled than are brought in, resulting in a resting membrane potential of approximately -70 mV.

The energy cost for maintaining the resting potential is high, as a neuron can use up to 50 percent of its ATP for this purpose alone.

Additionally, glial cells, such as astrocytes, play a role in maintaining ionic balance in the extracellular fluid, ensuring proper functioning of the resting membrane potential in neurons within the CNS.

User FObersteiner
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