No direct connections exist. Instead, as hairs are bent, nerve impulses are stimulated in the nerve fibers. The exact method of the electrical impulse generation is not known, although some theories exist. The changing stiffness of the basilar membrane from one end of the cochlea to the other creates a kind of mechanical analyzer of sound. High frequency sound causes the narrow basil end of the membrane to vibrate.
Medium frequencies cause the membrane in the middle cochlea to vibrate.
Low frequencies cause the whole membrane to vibrate. The cochlea is able to map frequencies onto certain locations on the basilar membrane. The sensation of pitch is a function of the location of the vibration on the the basilar membrane. Auditory nerves and the brain Nerve impulses are transmitted from the ear to the brain via the auditory nerves, one of the several sensory nerves that exists in the group of nerves known as cranial nerves. That is, the neuron itself provides the necessary energy to propel the impulse along the nerve.