Why I Sneeze, Shiver, Hiccup, and Yawn

Why I Sneeze, Shiver, Hiccup, and Yawn

You are playing hide-and-seek. You've found a good hiding place. You want to be as quiet as you can. All of a sudden- KA-CHOO! You sneeze. Everyone knows where you are. Why do you sneeze-even when you don't want to? You are eating lunch with your friends. You are in the middle of telling them a story. All at once you hiccup. HIC! Your friends start to laugh. HIC! You try to stop. HIC! But you can't. HIC! Why do you hiccup even when you don't want to?

A sneeze is a reflex. So is a hiccup. You don't have to think about making reflexes happen. They happen whether you want them to or not. They happen very fast, and it is hard to stop them. Shivering and yawning are also reflexes. All reflexes work through your nervous system.

Your nervous system is made up of two parts. One part is the nerves. The nerves look like long, thin threads. They reach all over your body. The other part is the spinal cord and brain. The spinal cord is a thick bundle of nerves. It is inside your spine, or backbone. The brain is at the upper end of the spinal cord. It is made up of billions of tiny nerves. Nerves are like telephone wires. They carry messages back and forth. The brain and spinal cord are like the main office of the telephone company. All the messages must go through here.

Suppose you put your finger on a hot stove. The nerves in your hand sense that the stove is hot. They send out a message. The message speeds along nerves from your hand to your spinal cord. Here the message passes to a different nerve. This nerve controls the muscles that move your arm. A signal flashes through the nerve. It tells your muscles to move your hand and fast. Before you even know what hurts, your hand jerks away from the stove.

Pulling your hand off a hot stove is a reflex. It happens very quickly, and it is not completely under your control. It happens automatically, without your having to think about making it happen.