What roles do the utricle and saccule play in the vestibular system?

The utricle and saccule are critical components of the vestibular system, which is responsible for maintaining balance and spatial orientation. Their primary role involves detecting linear accelerations and the position of the head in relation to gravity. The utricle is sensitive to horizontal movements, while the saccule responds to vertical movements.

These structures contain specialized sensory cells called hair cells, which are embedded in a gelatinous substance that is weighted with tiny calcium carbonate crystals. When the head moves or changes position, the fluid within the utricle and saccule shifts, causing the hair cells to bend. This bending generates nerve signals that are sent to the brain, providing information about the head's position and movements.

This function is essential for maintaining equilibrium, allowing the body to respond appropriately to changes in posture and movement. The output from the utricle and saccule is integrated with input from the visual and proprioceptive systems to coordinate balance and spatial orientation. This highlights the importance of the utricle and saccule in detecting movement and spatial orientation, making the second choice the correct one.