A pretty good bump on the head, or a violent collision, can leave you feeling woozy and confused, and with a splitting headache. If it's bad enough, you may even lose consciousness.

So, what causes a concussion?

Your brain is a delicate organ encased in bone, your skull. When you fall down, suffer violent contact during a sports activity, or hit your head in a car accident, your brain moves but has nowhere to go. Instead, it swirls around inside your head and bumps into your skull. This causes bruising that damages your brain.

The classic symptom of a concussion is loss of consciousness. But many people might experience only a brief moment of amnesia or disorientation. Typically, you'll have a headache, feel sleepy, and you may even vomit. Most likely you will not be able to think "straight," that is, maybe you can't remember the date or your name. You may see flashing lights and even feel like you've "lost time." Sometimes, it may take a day or two after the blow for some symptoms to develop.

Your doctor will do a physical exam, checking your pupils, your ability to think, your coordination, and your reflexes. The doctor may want to look for bleeding in your brain, so you may need a CT or MRI scan. You may also have a brain wave test, or EEG.

So, how do we treat a concussion?

First and foremost, you will need to rest and be watched -- sometimes in the hospital, and sometimes by a parent, friend, or spouse if you're at home.

For your headache, you can take acetaminophen. You may need to eat a light diet for a while if you continue to feel sick, or feel like vomiting. You'll want to have someone stay with you for the first 12 to 24 hours after your concussion. It's okay to sleep, but someone should wake you up every few hours and ask you a simple question, such as your name, and then watch you for changes in how you look or act.

Obviously, if you were playing sports when you received a concussion, you most likely will need to stop. Sometimes you can't return to a sport for weeks, or longer, especially if your symptoms don't improve. That's because once you've had a concussion, it's easier to get another one, and multiple concussions can lead to long-term brain damage.