Question

Which ion channels are responsible for maintaining the resting membrane potential? (A) Ungated channels (B) Voltage-gated channels (C) Ligand-gated channels (D) No ion channels are involved in maintenance of the resting membrane potential.

Short answer

The responsible ion channels are ungated channels (A).

Step-by-step solution

Identify the key concept

The key concept here is the 'resting membrane potential', which is the electrical potential difference across the membrane of a neuron when it is not actively sending a signal.

Understand the role of ion channels

Different ion channels regulate the movement of ions across the neuron's membrane. Some channels open or close in response to specific signals, while others are continuously open.

Evaluate the types of ion channels

Ungated channels, also known as leak channels, are always open and allow ions to move passively along their concentration gradient. Voltage-gated channels open or close in response to changes in membrane potential. Ligand-gated channels open or close in response to specific chemical signals. Option D suggests no ion channels are involved.

Determine the correct ion channels

The resting membrane potential is primarily maintained by ungated channels, as they allow passive movement of ions, especially potassium ions, which is crucial in maintaining the membrane potential.

Conclusion

Ungated channels are responsible for maintaining the resting membrane potential as they enable the passive and continuous movement of ions, particularly potassium, across the neuron's membrane.

Key concepts

Neuronal membrane dynamics

Neurons, like all cells, have a membrane that separates the inside of the cell from the outside environment. This membrane is crucial for many cellular functions and plays a key role in the neuron's ability to send signals.
The electrical charge difference across this membrane, known as the membrane potential, is essential for neuronal communication.
When a neuron is not actively sending a signal, we refer to this charge difference as the resting membrane potential.
This resting state is important because it sets the stage for the neuron to react quickly to signals when necessary.
In simple terms, think of the resting membrane potential as the battery charge of the neuron, ready to power a signal when needed.

Ungated ion channels

Ungated ion channels, also called leak channels, are always open. This is unlike other ion channels which may only open in response to specific signals.
These channels allow ions to move freely across the neuron's membrane based on their concentration gradients.
For the resting membrane potential, the movement of potassium ions through these ungated channels is especially important.
Since they are always open, they help maintain the continuous flow of ions, which balances the charges on either side of the membrane.

Potassium ion movement

Potassium ions play a crucial role in maintaining the resting membrane potential. Inside the neuron, there is a high concentration of potassium ions compared to the outside.
Ungated potassium channels allow these ions to move out of the cell, following their concentration gradient.
As potassium ions leave the cell, the inside becomes more negatively charged compared to the outside.
This movement of potassium is what largely creates the negative charge inside the neuron during its resting state.
This balance might seem delicate, but it's essential for the neuron's ability to perform its signaling functions efficiently.

Maintenance of membrane potential

Maintaining the resting membrane potential is a dynamic process that involves a balance between different ions moving across the neuron's membrane.
Beyond potassium, other ions like sodium also play a small role, but their channels are usually less permeable at rest.
Ungated ion channels are crucial because they allow for the passive, continuous movement of these ions to keep the membrane potential steady.
The Sodium-Potassium pump also contributes by actively transporting sodium out of and potassium into the cell, preserving the necessary concentration gradients.
Overall, the concerted effort of these elements ensures that the neuron is ready to fire an action potential when a signal arrives.
This readiness is fundamental for the rapid and efficient communication within the nervous system.