Thu July 05, 2012 By: Ashutosh Ray

we know that brain controls all our bodily poster and function then why cant we walk straight if we rotate our body for sometime in a circle ???

Expert Reply
Mon July 09, 2012
The motions of our bodies are detected by the vestibular system found in the upper part of our inner ear. When we spin in circles, we feel dizzy and lightheaded due to the vestibular system's nerve reactions to these unusual motions. The vestibular system senses motion through three semicircular canals that are at right angles to one another. These canals have hair-like sensory nerve cells and also contain a fluid called endolymph. Endolymph resists changes in motion, due to which it lags behind and stimulates hair cells to send nerve signals to the brain. Our brain interprets the nerve messages and knows which direction the head moved.

However, when we spin, our brain receives mixed messages. The endolymph slowly begins to move in the same direction we are spinning. As time goes by, the endolymph catches up to the rate of speed we are spinning and no longer stimulates the hair-like nerve cells. This causes our brain to quickly adapt to the nerve signals. However, when we stop spinning, the endolymph continues to move and stimulates hair cells in the opposite direction. These hair cells send wrong messages to the brain making it think that the head is still spinning although it actually has stopped. As a result of this inaccurate signal, we experience dizziness and are unable to walk straight.




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