Final answer:
The semicircular ducts in the inner ear are responsible for detecting rotational head movements or angular acceleration. These canals monitor changes in head positioning through the movement of fluid affecting hair cells in the ampulla.
Step-by-step explanation:
The correct answer to the student's question is the semicircular ducts. These structures within the inner ear are critical for detecting rotational head movements, known as angular acceleration or deceleration. Each of the three semicircular canals is filled with fluid and is precisely angled in three-dimensional space. When the head moves, the fluid inside these canals shifts, leading to the movement of hair cells in the base of each canal called the ampulla. The deflection of the hair cells, specifically the stereocilia that project into a gelatinous structure called the cupula, generates neural signals that are sent to the brain to interpret rotational movement.
For example, when you turn your head rapidly or drive around a corner, your semicircular canals are stimulated. The brain receives and processes this information, allowing you to maintain your balance and understand the movement of your head in space. This detection system is not sensitive to steady motion at constant velocity but to changes in velocity, such as starting, stopping, or changing direction.