Membrane potential

Published on June 29, 2022   28 min
Hello and welcome back to Fundamentals of Human Physiology. This activity is going to be about membrane potential.
Membrane potential means the electrical charge across the membrane of a given cell. Cells that have the ability to utilize that electric charge to send a signal of some sort, are called excitable cells. Now, the most obvious one we might think about is a neuron, but also muscle cells are excitable cells, many cells in our body are able to carry and utilize an electrical charge to send a signal.
Now, you might remember from our last lecture, we were talking about neurons. Just to get sort of the basic anatomy of a neuron out of the way, and you probably already know this, neurons generally look like this, but they can come in all different shapes and sizes. But for our purposes now, we'll look at a basic neuron that looks something like this. Its job is to carry a signal from point A to point B. Now, that signal was received here at the cell body, generally travels in from these dendrites to the cell body. That signal might come from another neuron or it could come from a hormone, etc. that's going to cause this neuron to be activated. Once activated, it will fire an action potential, we'll learn how that happens, where an electrical signal travels all the way down this axon to the end of the neuron, where it then communicates with the next cell. This next cell could be another neuron. It could be a muscle cell, it could be a gland where the neuron could be telling it to release a hormone, etc. Now, we'll talk about how all of that happens in little bits and pieces. But what we need to first figure out is what do we mean by an electrical signal? What is this electrical signal and how does a neuron, A, have the potential to do that, and B, get it to travel along the axon? Membrane potential means that it has the potential to generate an electrical signal, and membrane potential specifically is the charge that we measure across the membrane. We'll learn how all of that works on our way through this activity. But to do that, we're going to zoom in on just a little portion of this cell membrane, a little cross-section of the cell membrane, to start to understand how this works.