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Why do you feel dizzy when you spin around?

A child about to feel dizzyA child about to feel dizzyHave you ever had that feeling of being barely able to stay on your feet after getting off a spinning fairground ride? Feeling dizzy after experiencing an intense spinning motion is a common sensation, but what causes it? In fact, both an understanding of physics and biology are needed to explain dizziness. One of the fundamental laws of physics states that a body will remain at rest unless an external force is applied to it, and will remain in motion unless it is forced to halt. This resistance to any change to a body’s state of motion is called inertia. This, together with a complex system inside your inner ear, is the reason for dizziness.

The inner working parts of the earThe inner working parts of the ear


Vestibular system

In addition to hearing, your ears also give you a sense of balance. Inside your inner ear are three semi-circular canals, set at right angles to each other. They work together to orientate you correctly in 3D space. Every time your head moves, the flow of liquid within them is picked up by sensory hair cells. These send nerve signals to the brain, which then works out whether the body is upright or lying down and whether it is standing still or in motion—and if so, which direction that movement is. The brain then sends instructions to the muscles to adjust the position of the body if necessary. This is called the vestibular system.

The information about which way the hair cells inside the semi-circular canals are swaying at any given moment is relayed to the brain via approximately 20,000 nerve fibres.

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