What type of movement does the semicircular canals primarily detect?

The semicircular canals are key structures in the inner ear that are primarily responsible for detecting angular rotation or rotational movements of the head. These canals are arranged in three orthogonal planes, allowing the vestibular system to sense changes in head position and movement in three-dimensional space. When the head rotates, the endolymph fluid within the canals lags behind due to inertia, causing the movement of hair cells that are embedded in the ampulla of each semicircular canal. This mechanical stimulation converts angular motion into neural signals that are sent to the brain for interpretation, facilitating balance and coordination during activities like turning the head or spinning.

In contrast, the other types of movements mentioned, such as horizontal and vertical linear movements, are primarily detected by the otolith organs (the utricle and saccule), which respond to changes in position relative to gravity rather than rotational movements. Sound frequency is associated with the cochlea, which is responsible for hearing and not motion detection. Therefore, angular rotation is the correct answer as it directly corresponds to the primary function of the semicircular canals.