Hey there!  I'm sure you know, like Squeeks here does, that exercise is a really important part of keeping your body healthy and strong.  And whether you're running a race, playing football, or just doing a whole bunch of jumping jacks, exercise means moving.  And one SciShow Kids viewer named Autumn wants to know: How does my body move?  Really awesome question Autumn!

Your body is made up of lots of different parts that all have a very special job.  To help keep things organized, scientists sometimes group the parts of our bodies into what we call body systems.  And all of the parts in a certain body system work together to accomplish a goal.  When it comes to making you move it takes three body systems working together to get the job done.  They're called the muscular system, the skeletal system, and the nervous system.  Ready to check them out?

Lets start with the muscular system.  Your muscular system is made of, well, muscles.  Muscle is the stuff, what scientists call "tissue," that allows you to move around.  Muscles don't just help you to swing a bat, or jump to catch a ball.  Some muscles help you chew, wiggle your nose, stick out your tongue, or even blink.  And some muscles like the ones in your back and legs just help to hold your body upright so you can walk, run, or simply sit.  Muscle tissue is pretty flexible, kind of like thick rubber or elastic, and also like rubber, it can stretch and change shape.  Let's see how.

When you bend your arm at the elbow, a muscle called your bicep contracts or squeezes together.  When it contracts its shape gets shorter and thicker.  When you straighten your arm your bicep relaxes.  When a muscle relaxes its shape gets longer and thinner.  But muscles contracting and relaxing aren't enough to make us move.  They need to be attached to another part of our body to get the job done.  And that's where the next system, the skeletal system, comes in.

The main part of your skeletal system, the skeleton, is made of all your hard, sturdy bones.   Although we sometimes think of skeletons as dead things, especially around Halloween, that's actually not true.  Your bones are very much alive and they have many jobs.  One of the most important jobs is to support or hold up the rest of your body, and this includes your muscles.  Strong cords called tendons attach your muscles to your bones.  When a muscle contracts or relaxes it pulls the bone into a different position, which makes it move.  

But how do your muscles know they're supposed to move at all?  Well they know because they're under control of your nervous system.  The most important part of your nervous system is your brain.  Your brain is kind of like your body's command center.  When you decide to move, your brain sends signals to your muscles giving them specific instructions on what to do.  Say you're trying to pick up a snack.  Your brain sends signals to the muscles in your hand and wrist telling some of them to contract.  As the muscles contract they pull the bones in your fingers so that you can grab the apple.  Then your brain sends more signals to your arm muscles telling them to move the bones in your arm so that you can bring the apple right to your mouth.  Snack accomplished!

So it takes the actions of three body systems to help us move.  The muscular, skeletal, and nervous systems.  Autumn, thanks for watching SciShow Kids, and asking such a great question!  If anyone else has a question for any of us here at the fort let us know by leaving a comment or emailing us at kids@thescishow.com.  Thanks guys, see you later!