|MadSci Network: Neuroscience|
Nick, The short answer is nerves. I am sure you have heard of nerves before but perhaps you didn't know what they did. Basically all the information your body needs to do the things it has to do is transmitted from your brain and spinal cord by nerves. The brain is the portion of you that makes sense of the world around us and relays the proper information to the body to take proper action. You can try to imagine that the brain is the top of the spinal cord and sends nerves down through this cord like wires. These nerves then project out of the spinal cord and end on things like skin, muscle and internal organs. Some nerves carry information from these structures back to the brain so the brain can decide what to do like moving a muscle to move whatever part of the body is feeling the sensation. Here's an example that might help. Say you're walking barefoot in your living room and you step on a pin, OUCH! Now you can probably answer what you would do without knowing anything about nerves. You would quickly take all your weight off of the foot with the pin in it, balance on the other foot, and pull the pin out. Here is what is going on in your nervous system. Walking around the room your are already using certain nerves to make your muscles move the way you want them to and your balance is evenly on both legs(we'll get more into balance in a minute). The pin stabs your foot and activates the nerves that sense pain to transmit this information to your brain through your spinal cord. Now the real interesting thing is that not all nerves have to go to the brain in order to make your body move. These are called reflex nerves. Think about that, cause a reflex is something that you can't control and that is part of what is happening in this example. OK, the pain information goes to the spinal cord and brain, but it is in the spinal cord where the reflex action takes place. In the spinal cord the pain nerve splits into a few branches. Some of it continues to the brain for processing, but other fibers of that nerve connect to another type of nerve in your spinal cord called a motor nerve. The pain nerve "tells" the motor nerve what has happened using a special chemical, and this activates the motor nerves to make your leg muscles move so that you don't cause yourself more pain by stepping down harder on the pin. Your brain has processed the pain, recognizing the exact location of where it is so that you can then do something to stop the pain, like pull the pin out. Your brain tells motor nerves in your arms and hands to move to the pin, grab it, and yank it out! The amazing thing is how fast all of this happens. It takes very little time at all for your foot to signal your brain and spinal cord what is going on and for you to take action. Now, balance is also controlled through nerves, but it also has to do with your ears. Your ears actually can sense when the head is moving and send information to your brain so that you can adjust your body to keep from falling over. Your ear is a pretty complex structure inside that has fluid filled canals inside. When you move the fluid inside starts to move as well, signalling motion to your brain. What happens if you make a wave at one end of the bath tub? The wave heads off in the intended direction, hits the other side of the tub and bounces back and it keeps going for a while. Well the same thing happens in your ear when you move. With normal turns of the head the waves of fluid inide the ear are pretty small and subside quickly when you stop moving. But when you spin in a circle you really shake things up, and when you stop the fluid keeps going for a while, so your brain is still getting signals that you are moving, but your eyes and your body is telling the brain that your are not and some major confusion occurs. So you stumble around trying to stay up, but you fall over. The fluid in the ear eventually settles down and your body returns to its normal sense of balance. These are pretty simple explanations of these things, but they get the point across. I apologize for taking so long to answer your questions, and now I hope you now have an appreciation for how your body uses nerves to work. Mark Sullivan
Try the links in the MadSci Library for more information on Neuroscience.