action potential

What is an action potential?

An action potential is a localized short-term change in the electrical membrane potential of a neuron, which produces a new action potential in adjacent areas.

What is the main difference between action potentials and gradient potentials?

Action potentials are all-or-nothing signals that occur in fixed sizes, while gradient potentials can vary in magnitude and only affect short distances.

How does propagation occur in neurons?

Propagation occurs when an action potential generates a new action potential in adjacent portions of the neuron, allowing for the signal to travel long distances.

What are the states of the voltage gated sodium ion channel at resting potential?

At resting potential, both the activation gate and inactivation gate of the voltage-gated sodium ion channel are closed.

What is the threshold potential for sodium channels to open?

The threshold potential for sodium channels to open is -55 millivolts.

What causes depolarization during an action potential?

Depolarization during an action potential is caused by the influx of sodium ions into the cell.

What happens to potassium ions during repolarization?

During repolarization, potassium ions move out of the cell, making the inside of the cell more negative.

What is the concept of the refractory period?

The refractory period is the time after an action potential during which a neuron cannot fire another action potential.

How does the stimulus affect gated channels?

A change in voltage serves as a stimulus to open gated channels, allowing specific ions to pass through.

What triggers the closing of the inactivation gate of the sodium channel?

The inactivation gate of the sodium channel closes shortly after the membrane potential reaches its peak, specifically around +30 millivolts.

Why can’t an action potential move backward?

An action potential cannot move backward due to refractory periods in the previous segment, which prevents it from being triggered again until recovery.

Can you have a partial action potential?

No, action potentials are all-or-nothing; they cannot be partial or of varying sizes.

What is the role of voltage-gated potassium channels during an action potential?

Voltage-gated potassium channels open more slowly than sodium channels and allow potassium to exit, contributing to repolarization and hyperpolarization.

What happens at the peak of an action potential?

At the peak of an action potential, the sodium channels close, and potassium channels begin to open, leading to repolarization.

How do sodium ions move during depolarization?

Sodium ions move into the cell during depolarization down their concentration gradient.

What is hyperpolarization?

Hyperpolarization occurs when the membrane potential becomes more negative than the resting potential due to excess potassium ions leaving the cell.

Action potentials are initiated when the membrane potential reaches _____ millivolts.

-55

During depolarization, sodium ions _____ the cell.

enter

The _____ period is a phase where a neuron is unable to fire another action potential immediately after one has occurred.

refractory

The inactivation gate of the sodium channel closes when the membrane potential reaches approximately _____ millivolts.

+30

During repolarization, potassium ions move _____ the cell.

out of

Hyperpolarization makes the inside of the cell more _____ compared to the resting potential.

negative

An action potential is characterized by a rapid and _____ change in membrane potential.

temporary

Gated channels open in response to a change in _____ across the membrane.

voltage

The process where an action potential generates additional action potentials in adjacent areas is known as _____ propagation.

saltatory

Sodium channels open more _____ in response to membrane depolarization compared to potassium channels.

quickly