What type of acceleration does the Utricle and Saccule measure?

The Utricle and Saccule are part of the vestibular system located in the inner ear, specifically within the labyrinth. These structures play a crucial role in maintaining balance and spatial orientation by detecting linear accelerations and the position of the head relative to gravity.

They contain otolith organs that have tiny crystals, called otoconia, that respond to gravitational forces and linear movements. When the head moves, the inertia of the otoconia causes them to lag behind, affecting the hair cells in the Utricle and Saccule. This interaction allows them to sense not only linear acceleration but also the static position of the head in relation to upright; thus, they detect displacements as well.

The correct answer highlights the Utricle and Saccule's ability to measure both the linear accelerations of the body and the positions concerning gravity, making it suitable for the context of head movements and changes in speed or direction.