Voltage gated Channels and the Action Potential HD Animation

Summary

The script explains the process of action potential in neurons, starting with the resting membrane potential where voltage-gated sodium and potassium ion channels are closed. Depolarization occurs when a stimulus triggers sodium channels to open, allowing sodium ions to flow in, making the membrane potential more positive. As the potential reaches its peak, sodium channels' inactivation gates close, while potassium channels remain open, leading to repolarization as potassium ions exit the cell. The membrane potential briefly overshoots the resting value due to the prolonged potassium ion permeability. Finally, active transport restores the resting potential.

Takeaways

• 🔋 At rest, the cell membrane has a negative membrane potential due to the closed activation gates of voltage-gated sodium ion channels and open inactivation gates.
• 🚀 Depolarization begins when a stimulus makes the membrane potential more positive, triggering the opening of voltage-gated sodium ion channels.
• 🏁 The threshold for an action potential is reached when many sodium channels open, allowing sodium ions to rush in and cause depolarization.
• 🔄 Voltage-gated potassium ion channels open more slowly during depolarization, contributing to the repolarization phase.
• 💧 Depolarization occurs because sodium ions diffuse into the cell more rapidly than potassium ions diffuse out.
• 🔄 As the membrane potential nears its peak, the inactivation gates of sodium channels close, reducing sodium ion influx.
• ⏳ The potassium ion channels remain open longer than necessary to return the membrane potential to its resting state, causing a brief hyperpolarization.
• 🔙 The extra outflow of potassium ions helps to overshoot the resting membrane potential, making it slightly more negative temporarily.
• 🔄 After the voltage-gated potassium ion channels close, active transport mechanisms work to restore the resting membrane potential by moving sodium and potassium ions back to their original concentrations.
• ♻️ The entire process is a cycle that allows neurons to transmit signals through changes in membrane potential, known as action potentials.

Q & A

What is the resting membrane potential, and which ion channels are involved at this state?

At the resting membrane potential, the voltage-gated sodium ion channels' activation gates are closed, and the inactivation gates are open. The voltage-gated potassium ion channels are also closed.

How is depolarization initiated in a cell?

Depolarization is initiated by a stimulus that makes the membrane potential more positive, causing the voltage-gated sodium ion channels to start opening.

What happens when the threshold for depolarization is reached?

When the threshold is reached, many sodium channels open, allowing sodium ions to diffuse across the membrane, leading to depolarization.

Why does depolarization occur?

Depolarization occurs because more sodium ions diffuse into the cell than potassium ions diffuse out of it.

What changes occur in the sodium ion channels during maximum depolarization?

As the membrane potential approaches maximum depolarization, the inactivation gates of the voltage-gated sodium ion channels begin to close, decreasing the diffusion of sodium ions.

How do potassium ion channels contribute to the return to resting membrane potential?

The potassium ion channels remain open during depolarization, allowing potassium ions to continue diffusing out of the cell, which helps in returning the membrane potential to its resting level.

Why does the membrane potential become slightly more negative than the resting value after depolarization?

The extra efflux of potassium ions during the prolonged opening of potassium ion channels causes the membrane potential to become slightly more negative than the resting value.

What happens to the voltage-gated potassium ion channels after depolarization?

After depolarization, the voltage-gated potassium ion channels close, stopping the efflux of potassium ions.

How is the resting membrane potential reestablished after depolarization?

The resting membrane potential is reestablished through the active transport of sodium and potassium ions.

What is the role of the inactivation gates in the voltage-gated sodium ion channels?

The inactivation gates in the voltage-gated sodium ion channels play a role in stopping the further influx of sodium ions by closing as the membrane potential reaches maximum depolarization.

How do the voltage-gated sodium and potassium ion channels differ in their response to depolarization?

The voltage-gated sodium ion channels open more rapidly in response to depolarization, while the voltage-gated potassium ion channels open more slowly.