What structure in the ear is responsible for balance?

The semi-circular canals play a crucial role in maintaining balance and equilibrium. These structures are part of the vestibular system, located in the inner ear, and are filled with fluid. They are oriented in three different planes: horizontal, anterior, and posterior. When the head moves, the fluid within these canals shifts, causing movement of sensory hair cells. This movement is then translated into signals sent to the brain, which interprets these signals to help maintain balance and coordinate movements.

In contrast, the cochlea is primarily involved in hearing, converting sound vibrations into neural signals. The Eustachian tube helps equalize pressure in the middle ear and does not directly influence balance. The auditory nerve transmits sound information from the cochlea to the brain, playing a role in hearing rather than balance. Thus, the semi-circular canals are the key structure responsible for providing the brain with information about head position and motion, crucial for maintaining balance.