Reflexes: Moving without Thinking
If you touch a hot pan by mistake, you’d pull your hand away so quickly that at first, you may not even realize what happened! That’s an example of a reflex. Reflexes are very fast, automatic responses of the body that protect you from harm, help you adjust to changes, or help you move.
Reflexes are carried out by the nervous system. They consist of a very small number of nerves that carry signals between your muscles and your spinal cord. In general, our nervous system helps us do two kinds of actions: voluntary and involuntary actions. Anything you choose to do is a voluntary action, like deciding to take a bite of a sandwich. Involuntary actions are things that we do without needing to think, like your digestive system breaking down that sandwich. Reflexes are another kind of involuntary action. This is also why they are called “automatic.”
There are many kinds of reflexes in the body. Touching a hot pan and pulling your hand away is an example of a withdrawal reflex. Nerves in your skin feel the hot temperature and pain caused by the pan, and carry that information straight to your spinal cord. Then the nerves in your spinal cord send a signal straight back to the muscles in your hand to move away. Because there’s so few nerves and signals being sent, this reaction can happen very quickly, which helps protect you! The information doesn’t travel all the way up to your brain until after you move your hand, which is why you may not realize what happened right away.
As another example, if you hear a loud noise, you might jump and tense your muscles -- that’s called a startle reflex. You also have a blink reflex which protects your eyes. If any object touches your eyes, both of your eyelids will close at the same time. Your pupils will also shrink rapidly if you enter an area of bright light, in order to protect the cells inside of your eye, which is yet another reflex. Sighing, sneezing, coughing, and gasping are all reflexes that can interrupt your regular breathing patterns. You have a gag reflex too, where the muscles in the back of your throat contract, which is meant to keep you from choking.
At a regular check-up, your doctor might have tapped just below your knee to see if your leg kicks out. This is a test to see if something called your deep tendon reflexes (DTR) are working. They can also check this at the back of your elbow, the crook of your arm, wrists, or ankles. Doctors often check our reflexes because it’s one way to check that parts of our nervous system are working properly.
Even though we don’t often think about them, and don’t think to do them, reflexes are a part of our everyday lives and keep us safe!
