The fluids filling and surrounding it act as shock absorbers, and so do the
springy membranes which support it. It is even isolated from the normal body
supply lines, for the faint pulsing of blood through capillary vessels would be
detected as background noise.
The capillaries nearest to the organ of Corti end at the wall of the cochlea;
nutrients on their way out are carried to and from the capillaries by the
endolymph fluid that bathes the organ.
The organ of Corti is shaped like the jam in a jam roll. It spirals around
within the cochlea. The basilar membrane supports the organ which contains a
mass of cells almost touching the branch endings of the auditory nerve. From
these cells sprout fine hairs, (23,500 of them) rising in orderly rows like the
bristles of a very soft brush. The hairs stick through the dome of the organ,
their ends embedded in a thick overhanging sheet, the tectorial membrane.
These hairs are transducers. As the basilar membrane bellies in and out, it
pushes and pulls the complex of tissues above it.
The hairs' cells of the organ of Corti ride with the basilar membrane. The
hairs have their tops embedded in the tectorial membrane and their roots fixed
in the hair cells, so the motion of the basilar membrane bends and twists and
pulls and pushes the hairs. Under these physical stresses the hairs generate
electrical signals which stimulate the auditory nerve (also known as the
acoustic nerve and the eighth cranial nerve) - a bundle of about 30,000
individual fibres.
Eventually, in a way still not fully understood, the electrical signals running through the auditory nerve stimulate the hearing centres of the brain. In the cells of the auditory cortex lies the mystery of the sensation of hearing.
The organ of Corti serves two vital functions:
1 It Converts mechanical energy into electrical energy.As the organ of Corti, which is attached to the basilar membrane, bends to outside pressure, it moves laterally to the left whilst the tectorial membrane moves to the right.
2 It Dispatches to the brain a coded version of the original sound - information not only about fundamental frequency but about intensity and timbre as well.