Re: How is electricity used in your body?

Hi There!

Good question!

Electricity is used all around the body…..special nerves made up of cells called neurons carry electrical signals to the brain from every part of the body and from the brain to all parts of the body. These nerves even carry electricity from one part of the brain to another! One wonders, though……

Why is this?

We generally think that it's the way our brain helps us to get information from our senses, processes this information, and helps us control our muscles and organs. For example, when we touch something hot, like a stove, the nerves that send information from our senses (called sensory neurons) send an electrical signal to a part of our brain that helps control how we feel things. Our brain sends this information from this "feeling part" of our brain to the part that controls our movement (pretty much to say "move that hand!" ). This communication comes in the form of more electric signals. Finally, the part of our brain that controls movement sends…you guessed it….an electric signal through a nerve (called a motor neuron) connected to a muscle, which causes the muscle to contract and move your hand. All this happens in less than a second!

For something a bit more technical and specific….read on!

OK! For this last part, let's focus on the electricity in my personal favorite part of the body, the human brain!

The electricity used by neurons is called electrochemical, because it created chemically. Basically, the neuron is a cell surrounded by electrically charged particles called ions. Some of these ions have a positive charge, (like potassium and sodium) and some are negative (chloride is the biggie here). The electricity used by the neuron is kind of "borrowed" from these ions, depending on how many ions are inside or outside the neuron. For example, if there are more negative ions inside the neuron, the neuron has a negative electrical charge, if more positives are inside, then the neuron has a positive electrical charge.

How, you may ask, do these ions get in and out of the neuron?

Why, through gates, of course! Believe it or not, we actually call holes that are in the walls of the neuron gates (also sometimes called channels). These gates open or close to let some ions in or out depending on whether the neuron is going to send a signal or not. When the neuron is not busy sending signals, it is resting…right? During this time, the neuron is busy pumping out more positive ions (sodium), than it is letting in (potassium). This means that there are more positive charges outside than in, right? That makes the inside kind of negative! That means, that even when the neuron is not doing anything, it is still charged (about -70 millivolts, really)! Since the neuron is resting, we call this a resting potential.

Well, when the neuron gets information from, say, another neuron for example, the voltage changes a little (it becomes a little more positive….we call this depolarization). This doesn't really affect much unless, the voltage raises from -70 millivolts to -55 millivolts….it may take some input from a few neurons to do this! If, however, this threshold voltage of -55 millivolts is reached, the neuron leaps into action! The gates that let in the sodium ions (positively charged stuff) swing wide open and these little ions rush in, making the neuron more positive. The voltage which has crept from -70 millivolts to a measly -55 millivolts leaps to +30 millivolts (that's an increase of about 75 millivolts….pretty impressive considering that the neuron is a tiny little cell!) Considering all of this action, it's no surprise to hear that we call this voltage jump an action potential.

Pretty soon, the potassium gates open (more positive stuff), but instead of rushing in like the sodium did, these guys rush OUT! There are just too many positive particles inside, they have to get out….. charges with the same sign repel each other, just like magnets. At this point, the sodium gates close, so there's more positive stuff leaving than getting in, and the neuron starts pumping sodium out faster than it's pumping in potassium, just like before. So, the voltage begins to drop….past -55 millivolts, even past -70 millivolts for a very short time, then back up to -70 millivolts to where it started all over again!

If you want a bit more detail, click on this link for a closer look at the action potential…cool stuff.

I hope this answers your question…..come back if your curiosity gives you more to ponder!

Farewell,

Dr. Tom Virden