It was practically the last history class of the year. Ellen had done her homework, and she was anxious to be called on.

The teacher asked, "Where was the Constitutional Convention held?" Hands started waving all over the classroom. Ellen frantically waved her hand, too. Then before she knew what she was doing, she blurted out: "PHILADELPHIA! It happened in Philadelphia."

"That's the right answer, Ellen," her teacher said, "but you have the manners of a hippopotamus! In this class, we wait until we're called on to speak."

Ellen felt terrible. She hung her head, and her eyes filled up with tears for a second. She was so embarrassed! A hippopotamus! Her teacher had called her a hippopotamus.

She could feel her face flaming with a bright red blush. Her heart was pounding. Her palms felt sweaty. She wanted to leap up and run out of the room. But she just sat quietly until the end of class and then snuck away to the playground to be by herself for awhile.

The next day, Ellen's teacher seemed to have forgotten the incident. But Ellen couldn't. She kept going over and over it in her mind. She didn't raise her hand in class for a few days, even though history is her favorite subject.

Ellen's embarrassing moment happened a couple of weeks ago. But every time she thinks about it, her face turns bright red all over again. She feels flushed and hot. Her heartbeat seems to speed up. "I'll never be able to answer a question in history again," Ellen thought. "I wish I didn't blush so easily!"

Embarrassment can be a very powerful feeling. When you're experiencing it, it seems to block everything else out for a few seconds. It's an emotion strong enough to affect your body.

When you feel a strong emotion, your nervous system switches on two tiny little organs called the adrenal glands. The adrenal glands sit like little caps on top of each one of your kidneys. These small glands give off chemicals called hormones.

The adrenal glands make two kinds of hormones: adrenalin and noradrenalin. When they're released into your bloodstream, these two substances increase your heart rate, raise your blood pressure and make you produce more sweat. Your body automatically sends more blood rushing to your muscles and your brain. As the chemicals rush through your bloodstream, they can also make you breathe faster and feel kind of shaky. When your heart rate and blood pressure go up, more blood than usual reaches the surface of your skin.

If you're fair -- very light-skinned -- as Ellen is, the extra blood pulsing through small veins near the surface of the skin shows through the paper-thin outer layer called the epidermis. That's what causes the colorful blush.

As the rush of hormones fades, the blush fades, too. The heartbeat slows down to a normal rate, and the "crisis" is over.

It may seem like an overreaction for the body to get so fired up over a simple case of embarrassment. But the endocrine system -- the group of glands that regulates chemicals in the body -- can't really tell whether the crisis started by strong emotion is a major one or a minor one. The emotion happens, the system clicks on and BANG! Your body is on the alert.

This physical alarm system is like the "fight or flight" response in animals. An animal's nervous system clicks on to get it ready to run away, or to turn and fight for survival on a moment's notice. In human beings, the hormones released by the adrenal glands give the body the extra burst of energy and strength needed to respond to an emergency.

During the short time that the hormones are coursing through the bloodstream, people can run faster, fight harder or perform feats of strength that they couldn't usually manage. That moment could be something life-threatening -- like a car running a red light toward your bicycle. It could be something emotional -- like a fight with your best friend or bad news about someone in your family. Or the "emergency" can be an embarrassing incident at school.

Of course, knowing about the "fight or flight" response doesn't make an embarrassing moment easier. Ellen blushes a lot -- when she has to talk in front of a class, when she sees a boy she has a crush on in the hall or when she recalls that horrible moment in history class.

"Someday you'll forget all about it," Ellen's mom says. Ellen doesn't believe it. And some research supports her feeling. Studies have shown that people have more vivid memories of events connected with strong emotions. "I'll never be able to look at a hippo at the zoo again," Ellen says.

Tips for Parents

If your children are adolescent or pre-adolescent, the cry "I'm so embarrassed" is probably familiar. As youngsters begin to separate their identities from their parents', they often find the older generation excruciatingly embarrassing. And the hormonal storms that accompany this period of development don't help. But there's a book that might: "Growing and Changing: A Handbook for Preteens" by Kathy McCoy and Charles Wibbelsman, MD, (Perigee Books, $9.95) gives plain-spoken answers to questions kids ask about the physical and emotional changes they're going through. It could even help answer some questions that you find too embarrassing to talk about.

Catherine O'Neill is a free-lance children's writer based in Baltimore.