What are the primary behaviors mediated by the vestibular system

What are the primary behaviors mediated by the vestibular system?

The vestibular system mediates four kinds of behaviors.

  • 1. It controls the vestibulo-ocular reflex (VOR), an eye movement that compensates for head movement by moving the eye in the direction opposite to the head in order for the individual to see clearly during movement. If you stare at this page and move your head back and forth, you will be able to see the text clearly because you have a functional VOR. People with decreased or absent vestibular function complain of blurry vision and avoid moving their heads.
  • 2. Vestibular input contributes to balance. In the light, on a flat surface you can stand and walk well without any vestibular function. Decrease the light, or make the surface uneven or unstable, however, and you will rely on your vestibular function to help you maintain balance. Think of the time that you slipped on a wet floor or on ice and almost fell but pulled yourself upright. Think of the time that you learned to skate on ice or roller blades, or used a skateboard. You were able to perform those skills using vestibular function. People with decreased or absent vestibular function complain of imbalance or they walk with wide-based, ataxic gaits.
  • 3. Vestibular function contributes to spatial orientation—to the sense of being upright, the sense that you are moving or stationary, and your sense of how much and how far you have turned. When you took the elevator to a different floor, even though the elevator was an enclosed box and no visual cues were available to you, you could sense the motion of the elevator. Think of the time that you flew in an airplane and did not look out the window, yet you knew when the plane was turning or slowing to land. You knew those things because you used your vestibular function. Ice skaters, dancers, skiers, and skateboarders all use vestibular function to know when they are upright or upside down in the air. Pilots use their vestibular function to help them stay oriented in conditions of reduced visual information. People with reduced or absent vestibular function may not be able to perform those skills. They may feel or look tilted and they may have either a constant sense of motion, known as vertigo , or a sense that the rest of the world is moving, known as oscillopsia . Oscillopsia may be mimicked clinically by closing one eye and moving the open eye with a finger on the eyelid, causing an oscillatory movement of the visual image.
  • 4. Vestibular function helps to modulate some vasovagal responses. When you ran a race, such as the 50-yard dash in school, you used vestibular function to modulate your heart rate, breathing, sweating, and other autonomic functions to increase blood to your muscles and oxygen to your lungs, to cool off your body, and to stop digesting your food. An acute attack of vertigo may be characterized by nausea or vomiting, increased heart rate and respiration, and sometimes the need to urinate or defecate.
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