Frank Loreti, age 12, of Uniontown, Pennsylvania, for his question:

What hart of the ear keeps our balance?

The walnut sized inner ear is packed with mini sized equipment and buried in the skull. Its three main compartments are the semicircular canals, the vestibule and the graceful cochlea. Its semicircular canals loop out from the central vestibule and connect with the middle ear, which is tucked between the eardrum and the inner ear. These three tiny looped canals are the sensitive organ of balance.

They are expertly arranged to keep checks on the body's balance in three directions. Two are more or less vertical loops, one is horizontal. Together they check the body's balance up and down, sideways, forward and backward. The tiny canals are partly filled with liquid that jogs around with motion. These changes are sensed by hair cells, attached to nerve fibers at the end of each canal. The nerves flesh this data to the brain, which keeps a constant check on the body's balance. When an upset is indicated, orders to readjust weight and balance are flashed to dozens of muscles throughout the body.