The Balance System

How does the balance system work?

Balance is defined as the ability to maintain the body's center of mass over its base of support ¹. An individual with a healthy balance system is able to maintain visual focus while moving, navigate uneven surfaces without difficulty, and make automatic postural adjustments to maintain balance during everyday activities. Balance is achieved by a complex interaction of sensory and motor systems and depends on three components: 1. The ability of the body's sensory systems to determine position in relation to the surrounding environment, 2. The ability of the brain to accurately process and integrate the information received from the sensory systems, and 3. The ability of the body's muscles and joints to maintain the movements required for balance. In a healthy individual, these systems work automatically to maintain balance; however, when one or more component is disrupted, the individual may experience disruptions to balance in his/her activities of daily living.

The role of the vestibular system

The vestibular system consists of three components: 1. A peripheral vestibular system (utricle, saccule, and 3 semicircular canals), 2. A central processing system (brain), and 3. A motor output system (postural control and eye movements). The peripheral vestibular system (inner ear) is important for balance and postural control as it has both sensory and motor components. When it functions as a sensory system, the vestibular system provides the brain with information regarding head position, head movement, and the direction of gravity. The motor components of the vestibular system allow it to produce reflexes for equilibrium and gaze stabilization. An individual who is diagnosed with a vestibular disorder has disruptions to his/her inner ear and, as a result, report symptoms such as dizziness, vertigo, nausea, headaches, and imbalance.

1. Shumway-Cook A, Woollacott MH. Motor Control: Theory and Practical Applications. Philadelphia: Lippincott, Williams & Wilkins; 2001. ↩