Vestibular System

Vestibular System

Athletes must accomplish amazing feats of balance and coordination of the body. As scientist, Mikhail Tsaytin discovered in the 1970s, acrobats can successfully make a two person human tower in the dark, but after adding a third acrobat, not even the most talented can maintain the balance required to keep the tower intact while in the dark (1). What does darkness have to do with it? The point is that balance relies on at least three signals coming from the body, and one of those is sight. Once you eliminate one of these signals, the body cannot accomplish the required task. In addition to sight, signals coming from muscles and joints, called proprioceptors are sensitive to changes in position. The third contributor to the human tower and the topic of discussion of this paper is the vestibular system. A three-person human tower in the dark must not have enough information coming from the vestibular and proprioceptive systems to function without vision, whereas the two-person tower did have enough information.

The ear houses some of the most sensitive organs in the body. The physics of sound is well understood, while the mechanics of how the inner ear translates sound waves into neurotransmitters that then communicate to the brain is still incomplete. Because the vestibular labyrinth and the auditory structure are formed very early in the development of the fetus and the fluid pressure contained within both of them is mutually dependant, a disorder in one of the two reciprocating structures affects the (2).

The vestibular system accomplishes three tasks. First, it contributes to an individualís sense of equilibrium in relation to the force of gravity and thus adds to the subjective sense of motion and spatial orientation. Second, inputs coming from the vestibular system convey information to the bodyís muscles and posture. Third, while head and body are in motion, the vestibular system controls eye movements so that images remain steady and in focus. This is called the vestibular-ocular reflex.

These tasks are accomplished through the mechnoreceptors of the three semicircular canals, the utricle and the saccule (3). Like the neighboring auditory system, each canal has hair cells that detect minute changes in fluid displacement, but unlike the auditory system, the utricle and the saccule send information to the brain regarding linear acceleration and head tilt. Shaking your head ënoí employs one of these canals. Likewise, there is a canal that detects head movement in the ëyesí position, and there is yet another semicircular canal that detects motion from moving your head from shoulder to shoulder (4).