towards an analysis of errors made by university students ... - DSpace

information from the outside world and send it back to the brain.
The eye has special nerves which are sensitive to. light. At the
back of the eyeball there.is a layer called the 'retina' containing
millions of nerve cells which react to light rays, almost like
the film in a camera. The lens of the eye puts a sharp
picture
of the outer world on the nerve cells of the retina. Each cell
which sees a spot of light sends a signal back to the brain,
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where the pictures are put together as a complete mental picture.
In the ear are nerves which react only to the
energy
of sound waves in the air. The outer ear helps to collect the
sound waves and concentrate them on the eardrum. The thin,
flexible drum moves back and forth in time with the sound waves.
The tiny vibrations on the eardrums are passed through a series
of small bones to the inner ear. In the inner ear is a spiral,
shell-like structure - the cochlea. Each nerve in this structure
reacts to the sound waves of only one frequency. The
brain
recognizes the signals from these nerves as sound-music, the
human'voice, thunder, the dinner bell, etc. The inner ear
also
contains a special group of nerves that are not connected with
the sense of hearing. These nerves are attached to three
tiny
doughnut-shaped hollow tubes called the 'semicircular canals'.
All three tubes are filled with a liquid. When you move your
head, the liquid moves, too. The signals from these nerves
help
us to keep our
balance.
Other kinds of nerves in the tongue and in the nose
detect the presence of certain molecules. Thus, we can
taste
and smell different substances. Special kinds of nerve cells in
the skin detect heat, cold, pressure or pain. These nerves are