What are the semi-circular canals primarily responsible for?

The semi-circular canals are integral components of the vestibular system, which plays a crucial role in maintaining equilibrium and balance. These structures are located in the inner ear and are filled with fluid. When the head moves, the fluid within the semi-circular canals moves as well, causing the hair cells within these canals to bend. This bending sends signals to the brain about the position and motion of the head, allowing the body to maintain balance and coordinate eye movements with head movements.

This function is essential not only for standing upright and walking but also for performing complex movements without losing balance. Therefore, their primary responsibility is for equilibrium and balance, confirming that the correct answer is indeed focused on this aspect rather than sensation, sound transmission, or taste.