Kelley McConnell, age 13, of Shreveport, Louisiana, for her question:

What happens when you get hiccups?

It happens when several pieces of internal equipment go on a rollicking, hic hiccupping spree. Normally the diaphragm puffs and blows in regular rhythm and the larynx politely waits for permission to speak. But sometimes an irritation of some sort upsets this trio of smooth performers    and they become involved in an attack of the hiccups.

The body carries on an amazing assortment of highly complex operations and all the operating equipment is packed into a very small space. For example, the voice box shares space in the neck with the breathing and eating tubes. The stomach crowds close to the lower breathing apparatus. Normally there is enough room for everything to run smoothly. But a slight irritation can start a hiccup spasm among a series of close neighbors.

The spasm is a jerky reflex of the diaphragm. This is the mighty, dome shaped muscle that works like a bellows to regulate the breathing. It works automatically, contracting to expel stale air from the lungs and relaxing to let in the next batch of fresh air. When all goes well, the diaphragm works in a smooth regulated rhythm, with no instructions from the conscious mind. However, apparently it is highly sensitive about what goes on among its crowded neighbors.

Perhaps a tickle attacks the throat or a crumb goes down the wrong way. An event of this sort is enough to upset the diaphragm and throw it completely off schedule. Suddenly it contracts like a fierce fist and this spasm repeats again and again. Naturally its mighty muscular spasms trigger a sort of chain reaction among its neighbors.

With each contraction, air is jerked from the lungs down the wind pipe. Into this tube are crowded the vocal cords and the larynx, alias the voice box. There is also a neat little flap of moveable skin called the epiglottis. This is cunningly placed where it can stop bits of food from taking a detour down through the breathing pipes. The hic in the hiccup is produced by the epiglottis and the vocal cords.

Each time the diaphragm contracts, it pulls air into the larynx and perks shut the epiglottis. The air bashes against the closed epiglottis and swacks the vocal cords. This fast double beat creates the uncontrollable syllables that sound like "hic cup."

The contractions of the muscular diaphragm are governed by a network of automatic nerves. When certain irritations occur, signals are confused and these nerves go out of control. This creates a spasm in the diaphragm that smashes a gulp of air against the vocal cords and the closed epiglottis. And the hiccup repeats and repeats until the nervous nerves calm down and return to normal duty.