Balance system

How does my body keep its balance?

Your sense of balance relies on a series of signals to the brain from several organs and structures in the body, which together are known as the vestibular system. The vestibular system begins with a maze-like structure in your inner ear called the labyrinth, which is made of bone and soft tissue.

Within the labyrinth are structures known as semicircular canals. The semicircular canals contain three fluid-filled ducts, which form loops arranged roughly at right angles to one another. They tell your brain when your head rotates or moves up or down. Inside each canal is a gel-like structure called the cupula [KEW-pyew-lah], stretched like a thick drumhead across its duct. The cupula sits on a cluster of sensory hair cells. Each hair cell has tiny, thin extensions called stereocilia that protrude into the cupula.

When you turn your head, fluid inside the semicircular canal moves, causing the cupula to flex, which bends the stereocilia. This bending creates a nerve signal to the brain to tell it which way your head has turned.

Between the semicircular canals and the cochlea lie two otolithic [oh-toe-LITH-ic] organs: fluid-filled pouches called the utricle [YOU-trih-cull] and the saccule [SACK-kewl]. These organs tell your brain the position of your head with respect to gravity, such as whether you are sitting up, leaning back, or lying down, as well as when your head is moving in a straight line, such as up, forward, or sideways.

The utricle and the saccule also have sensory hair cells lining the floor or wall of each organ, with stereocilia extending into an overlying gel-like layer. Here, the gel contains tiny, dense grains of calcium carbonate called otoconia [oh-toe-CONE-ee-ah]. Whatever the position of your head, gravity pulls on these grains, which then move the stereocilia to signal your head’s position to your brain. Any head movement creates a signal that tells your brain about the change in position.

When you move, the vestibular system detects mechanical forces, including gravity, that stimulate the semicircular canals and the otolithic organs. These organs work with other sensory systems in your body, such as your vision and your musculoskeletal sensory system, to control the position of your body at rest or in motion. This helps you maintain stable posture and keep your balance when you’re walking or running. It also helps you keep a stable visual focus on objects when your body changes position.

When the signals from any of these sensory systems malfunction, you can have problems with your sense of balance. If you have additional problems with motor control, such as weakness, slowness, tremor, or rigidity, you can lose your ability to recover properly from imbalance. This raises the risk of falling and injury.

Source: NIDCD (NIH)1

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References

  1. Source: NIDCD (NIH): nidcd.nih.gov/ health/ balance-disorders
  2. Source: GTR (NCBI/NIH): ncbi.nlm.nih.gov/ gtr/ conditions/ CN001866/ 
  3. Source: MedLinePlus (NIH): medlineplus.gov/ woundsandinjuries.html

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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.