Anatomy - Action Potential Quiz

What happens when a neuron is stimulated enough?

It fires an electrical impulse that zips down its axon to other neurons

How many signals can a neuron send?

One signal that only transmits at one uniform strength and speed

What is an action potential?

an electrical impulse in a neuron’s axon when stimulated enough that communicates with other neurons

What is the neuron like at rest?

The inside is more negative than the outside. It’s “charged up” and waiting for a signal.

What starts an action potential?

A stimulus (touch, sound, chemical, etc.) makes sodium channels open, letting positive ions rush in and make the inside positive.

How does the action potential move down the axon?

The positive charge triggers the next section of the axon to open its channels, creating a wave of electrical change traveling down.

What happens after the signal passes?

Potassium ions leave the cell to make the inside negative again. The neuron returns to resting state.

What is the overall pattern of an action potential?

Resting (negative) → depolarization (positive rush in) → signal travels → repolarization (positive leave) → back to resting.

Depolarization

inside of the neuron goes from negative to positive.

What does the sodium–potassium pump do?

Moves 3 sodium ions out and 2 potassium ions in to keep the neuron’s charge balanced. This keeps the neuron ready to fire.

What are ion channels?

Tiny “doors” in the neuron’s membrane that let ions move in and out.

What are voltage-gated channels?

Ion channels that open when the neuron reaches a certain charge (threshold). This lets ions move and starts an action potential.

What are ligand-gated channels?

Channels that open when a chemical attaches to them.

What are mechanically-gated channels?

Channels that open when the membrane is pressed, stretched, or touched

Simple summary of how neurons fire

The neuron is “charged” at rest → channels open → ions move → action potential happens → neuron resets.

What is threshold potential

The minimum level of stimulation a neuron needs to reach before it fires an action potential.

What does the body use to separate charges?

Membranes

What is on the outside of a cell?

Sodium (Na) ions that are POSITIVE

What is in the inside of a cell?

Potassium (K) ions that are NEGATIVE

What provides the potential to convert electricity into something useful?

Currents

What does a current do?

It indicates the flow of positively or negatively charged ions across the resistance of your cells membranes

What is voltage?

the measure of potential energy generated by separated charges

What is current?

the flow of electricity from one point to another (related to its voltage and resistance)

What is resistance?

Whatever is getting on the way of a current

What does polarized mean?

The neuron’s inside is negative compared to the outside (normal resting state).

What is depolarization?

The inside of the neuron becomes less negative (more positive) when sodium (Na⁺) enters.

What is repolarization?

The neuron returns back to negative after depolarization, when potassium (K⁺) leaves.

What is hyperpolarization?

The inside becomes more negative than –70 mV because K⁺ channels stay open too long.

What is threshold?

The charge needed to start an action potential, usually –55 mV.

What is an electrochemical gradient?

The combined force that moves ions in or out of a cell. It includes the electrical gradient (opposite charges attract) and the chemical gradient (ions move from high to low concentration).