Change in Membrane Potential - Online Tutor, Practice Problems & Exam Prep

Membrane potential changes are crucial for neural communication, involving resting membrane potential at -70 millivolts. Neurons can undergo depolarization, where the inside becomes more positive, and repolarization, returning to resting potential. Hyperpolarization occurs when the membrane potential dips below -70 millivolts. Understanding these terms—polarized, depolarization, repolarization, and hyperpolarization—facilitates comprehension of graded and action potentials, essential for neuronal signaling and overall nervous system function.

Change in Membrane Potential

So this video is going to be about changes in membrane potential. Now, you guys all know about resting membrane potential, right? But neurons can't stay resting forever. Eventually, that membrane potential has to change. And when that happens, we can get 2 types of signals. The first is called a graded potential and the second type, you've already heard of this, I bet, is called an action potential. Now we're gonna have quite a few detailed videos talking about each of those moving forward, but first, we're gonna cover some important terminology that's gonna help you understand when we're talking about neural communication.

So our first term that we have here is polarized, as in the neuron is polarized. And what this means is that the inside of the membrane is negative. I'm going to put a little negative sign right there and you can see this is not just any old negative. This is negative 70 millivolts, which we know is resting potential. Right? So a neuron that is polarized is a neuron that is at rest. So I'm actually gonna draw a little graph for us really quick just to help us visualize this. I'm gonna put negative 70 down here. We'll put a little dotted line and I'll put something positive up here. I'll do positive 20. Alright. So if we are polarized we are just hanging out right here at negative 70 and we're resting.

Now, sometimes our neuron will depolarize, or will have a depolarization. What that means is that the inside of our membrane is becoming more positive. So we're going to give it a positive sign right there and this would look literally just like this. So we are spiking and we're getting more and more positive in our membrane. This is sometimes called a temporary decrease in membrane potential. So, I always remember that we depolarize to decrease the membrane potential. Okay?

Now, once we're up here, our neuron doesn't want to stay up here forever. Neurons like to be negative where they can rest. Right? So, eventually we're gonna have a repolarization, and that is when the inside of our membrane becomes more negative. So, he's getting a negative sign right there and that would look just like that. So here, well, how I like to remember this is that we repolarize to return to rest. So we're going back down, down, down toward negative 70 millivolts.

Now, sometimes neurons, when they're trying to repolarize, they get a little too excited and they kind of overshoot that and so they kind of dip below negative 70 and that is called a hyperpolarization. So a hyperpolarization is when the inside of our membrane becomes more negative than resting potential. You can think of this as, like, hyper kind of means too much of something. Right? And in this case, it's too much negativity. So we're gonna give him double negative signs. He is too negative and this is sometimes called a temporary increase in membrane potential. Okay? So that's kind of us swooping a little bit too low there.

Now, I would highly encourage you to take your time with these terms. Make sure that you understand them because moving forward, understanding neural communication will be much easier if you can hear one of these words and immediately know what is happening to that membrane potential. So study these, take your time with them, and when you're ready, I'll see you in our next video. Bye-bye.

Change in Membrane Potential Example 1

Okay. So in this example, we have this nice graph here and along the x-axis we have our membrane potential plotted and along the y-axis we have time. And you can see this change in membrane potential has been plotted on the graph and so what we're going to do is fill out the vocabulary term that corresponds to each of those changes in the membrane potential. So let's dive right in and we're going to start down here sitting pretty at negative 70 millivolts which we know is resting potential and a neuron at rest is a neuron that is polarized. Right?

So we're going to start with our neuron polarized. Now, here along this blue line, we can see we're getting more and more positive and the only term here that describes our membrane getting more positive is depolarization. Right? So this is the depolarization that we're looking at here and then whoop here we go we're getting back down toward those negatives which must be our repolarization. Right?

We repolarize to return to rest. We're trying to get back down here to negative 70 and then whoops right there looks like we overshot that and we got too negative. So that is our hyperpolarization. Remember, hyper is, like, too much of something, so we actually got too negative and that's what that looks like, dipping down below negative 70. So there you have it.

We start off polarized at resting potential. Here we have the depolarization phase, our neurons getting more and more positive. Here is our repolarization phase, we're getting back down into those negatives, and we overshot that a little bit and ended up hyperpolarizing very briefly. So there you go and I will see you guys in our next video. Bye bye.

A neuron's membrane potential goes from -90 mV to -10 mV. Which of the following terms describes this change?

• A. Hyperpolarization.
• B. Polarization.
• C. Depolarization.
• D. Repolarization.

Here’s what students ask on this topic:

What is the resting membrane potential and why is it important?

The resting membrane potential is the electrical potential difference across the neuronal membrane when the neuron is not actively sending a signal. It is typically around -70 millivolts (mV). This negative charge inside the neuron is crucial because it sets the stage for the generation and propagation of electrical signals, such as action potentials. The resting membrane potential is maintained by ion channels and pumps, particularly the sodium-potassium pump, which helps to keep the inside of the neuron negatively charged relative to the outside. Understanding this concept is fundamental for grasping how neurons communicate and process information.

What happens during depolarization in a neuron?

During depolarization, the inside of the neuron's membrane becomes more positive compared to the resting membrane potential. This occurs when sodium (Na⁺) channels open, allowing Na⁺ ions to flow into the cell. As a result, the membrane potential moves closer to zero and can even become positive. Depolarization is a critical step in the generation of an action potential, which is the electrical signal that neurons use to communicate. This process is essential for the transmission of information within the nervous system.

What is repolarization and how does it occur?

Repolarization is the process by which the neuron's membrane potential returns to its resting state after depolarization. This occurs when potassium (K⁺) channels open, allowing K⁺ ions to flow out of the cell. As K⁺ exits, the inside of the membrane becomes more negative, moving back toward the resting membrane potential of -70 millivolts (mV). Repolarization is crucial for resetting the neuron's membrane potential, allowing it to be ready for the next action potential.

What is hyperpolarization and what causes it?

Hyperpolarization is when the membrane potential becomes more negative than the resting membrane potential, typically dipping below -70 millivolts (mV). This occurs when there is an excessive outflow of potassium (K⁺) ions or an influx of chloride (Cl^-) ions. Hyperpolarization makes it more difficult for the neuron to reach the threshold needed to generate an action potential, thus temporarily inhibiting neuronal activity. This process is important for regulating the excitability of neurons and ensuring proper neural function.

How do graded potentials differ from action potentials?

Graded potentials and action potentials are two types of electrical signals in neurons. Graded potentials are changes in membrane potential that vary in size and are not all-or-nothing. They occur in the dendrites and cell body and can be either depolarizing or hyperpolarizing. In contrast, action potentials are all-or-nothing events that occur when the membrane potential reaches a certain threshold, typically around -55 millivolts (mV). Action potentials are generated at the axon hillock and propagate along the axon without decreasing in amplitude, ensuring reliable signal transmission over long distances.