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Spinning and Unspinning

In this activity, students experiment with spinning to test the vestibular system in their ears which helps them balance... ears do MORE than hear.

Balance depends on:

  • visual information
  • "feedback" from muscles
  • information from the semicircular canals in the ear.

The “hidden sense” of balance is controlled by this vestibular system and is sometimes known as equilibrioception. The vestibular system registers the position of one’s body in relation to gravity and lets you know if it is moving or still, or speeding up or slowing down i.e. motion and position.

In the inner ear, there are three small loops above the cochlea called semicircular canals. These make up the vestibular system, along with the vestibular nerve.

The three small looping semicircular canals that sit above the cochlea, and like it, are filled with liquid and have thousands of microscopic hairs. When you move your head, the liquid in the semicircular canals moves, too. The liquid moves the tiny hairs, which the cochlea translates into a nerve message to your brain, about the position of your head. In less than a second, your brain sends messages to the right muscles so that you move to keep your balance.

Where does dizziness come in?

Sometimes the liquid in your semicircular canals keeps moving after you have stopped moving, for example, after spinning around. The hairs inside the canals are sensing movement even though you are standing still. That is why you might feel dizzy; your brain is getting two different messages and is confused about the position of your head. Once the fluid in the semicircular canals stops moving, your brain gets the right message and you regain your balance.

Objectives

  • Explore how the body’s sense of balance operates.

Materials

  • Per Group or Student Pair:
    spinning platform or office chair
    cup
    water

Key Questions

  • Why is a sense of balance important?Which parts of the body contribute to the vestibular system?
  • Which parts of the body contribute to the vestibular system?

What To Do

  1. Let each student spin, using an office chair or spinning platform, and then jump off to see if they feel dizzy.
  2. Show the students what is happening in their inner ear. Fill a cup halfway with water. Move the cup around in a circle in front of you and then stop. The water keeps swishing around, even after the cup is still. Explain that when you move your head, the liquid in the semicircular canals moves, too. After spinning around, the liquid in your semicircular canals keeps moving after you have stopped moving. The hairs inside the canals are sensing movement even though you are standing still. That is why you might feel dizzy; your brain is getting two different messages and is confused about the position of your head.
  3. Repeat the experiment but tell the students to spin one way and then the other. Ask if they still feel dizzy when they stop spinning. (Spinning the opposite way may help the fluid in the inner ear to stop “swishing” around more quickly. However, prolonged spinning in the opposite direction may cause the fluid to flow more forcefully in that direction, inducing dizziness – again – when the student stops spinning).