Neuron Resting Membrane Potential

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Questions and Answers

What is the main reason for the negative membrane potential in a resting neuron?

Open sodium channels

Influx of sodium into the cell

Efflux of potassium out of the cell (correct)

Presence of chloride channels

What is the purpose of the Na+/K+-ATPase pump in the neuron?

To balance ion leak through open channels (correct)

To maintain the resting membrane potential

To establish concentration gradients

To generate action potentials

Which ion has a greater flux out of the cell in a resting membrane?

Potassium (correct)

Chloride

Sodium

Calcium

What happens to the concentration gradient for chloride ions in a resting neuron?

It shifts until equilibrium potential is reached Signup and view all the answers

What is the relationship between the resting membrane potential and the equilibrium potential for potassium?

The resting membrane potential approaches the equilibrium potential for potassium Signup and view all the answers

What is the equilibrium potential for an ion?

The membrane potential when the ion is the only permeating ion Signup and view all the answers

What is the driving force behind the diffusion of chloride back into the cell?

The electrical potential difference Signup and view all the answers

What is the dynamic balance in a steady-state resting neuron?

Ion movement by the Na+/K+-ATPase pump equals ion leak through open channels Signup and view all the answers

What happens to the positive charge inside the cell when a graded potential occurs?

It flows away from the depolarized region Signup and view all the answers

What is the direction of positive charge flow outside the cell during a graded potential?

Towards the depolarized region Signup and view all the answers

What is the effect of graded potentials on adjacent membrane sites?

They become less polarized Signup and view all the answers

How far do graded potentials typically propagate?

Up to a few millimeters Signup and view all the answers

What determines the magnitude of a graded potential?

The initiating event Signup and view all the answers

What is the direction of graded potentials?

Either depolarizing or hyperpolarizing Signup and view all the answers

What is the characteristic of the local current in a graded potential?

Decremental Signup and view all the answers

Why do graded potentials die out quickly?

Because of the cell membrane's leakiness to ions Signup and view all the answers

What is the primary function of the sodium-potassium pump?

To pump sodium out of the cell and potassium into it Signup and view all the answers

What determines the membrane permeability to different ions?

The number of open channels for each ion in the plasma membrane Signup and view all the answers

Which ion is also a factor in generating the resting membrane potential in some cells?

Chloride Signup and view all the answers

What happens when potassium channels are opened in a cell membrane?

Potassium ions diffuse down its concentration gradient from compartment 2 into compartment 1 Signup and view all the answers

What is the result of potassium ions diffusing down their concentration gradient?

A potential difference across the membrane Signup and view all the answers

What is necessary for the generation of a resting membrane potential?

All of the above Signup and view all the answers

What is the role of the Nernst equation in the context of the resting membrane potential?

It determines the equilibrium potential of an ion Signup and view all the answers

What is the equilibrium potential of an ion?

The potential at which the ion is in equilibrium across the cell membrane Signup and view all the answers

Study Notes

The Resting Membrane Potential

The resting membrane potential is determined by the concentration gradients of sodium and potassium ions.
There is a greater flux of potassium out of the cell than sodium into the cell due to the greater number of open potassium channels than sodium channels.
This results in a significant negative membrane potential, approaching the potassium equilibrium potential.
In the steady-state resting neuron, the flux of ions across the membrane reaches a dynamic balance, with a small but steady leak of sodium into the cell and potassium out of the cell.
The Na+/K+-ATPase pump balances the rate at which ions leak through open channels, maintaining the concentration gradients.

Chloride Ions

Chloride ions also play a role in the resting membrane potential.
In cells without chloride-ion pumps, chloride concentrations shift until the equilibrium potential for chloride is equal to the resting membrane potential.
The negative membrane potential determined by sodium and potassium moves chloride out of the cell, resulting in a lower concentration inside the cell than outside.
This concentration gradient produces a diffusion of chloride back into the cell, opposing the electrical potential.

Graded Potentials

Graded potentials occur when a region of the membrane is depolarized, causing charge to flow between the depolarized region and adjacent areas at rest.
Positive charge flows through the intracellular fluid away from the depolarized region and toward more negative areas.
Simultaneously, positive charge flows outside the cell from more positive regions toward less positive regions.
This local current produces a decrease in charge separation, allowing the signal to move along the membrane.
Graded potentials can occur in either a depolarizing or hyperpolarizing direction, and their magnitude is related to the initiating event.
The signal decreases as distance from the initial site increases due to the leaky nature of plasma membranes.

Ion Concentrations and Pump

The concentration differences for sodium and potassium are established by the action of the sodium-potassium pump (Na+/K+-ATPase).
The pump pumps sodium out of the cell and potassium into it.
The magnitude of the resting membrane potential depends on differences in specific ion concentrations and membrane permeabilities to different ions.

Ion Channels and Permeability

The membrane permeability to different ions reflects the number of open channels for each ion in the plasma membrane.
Sodium, potassium, and chloride ions are present in the highest concentrations, and their membrane permeability is independently determined.
In some cells, chloride ions also play a role in generating the resting membrane potential.

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Description

Learn about the concentration gradients that determine the equilibrium potentials for ions and how they affect the resting membrane potential in neurons.