Question

Describe the roles of vision and the vestibular apparatus in a coordinated act in sports, such as a second baseman's double play, a pole vault, or a turnaround jump shot. What are the differences and similarities in the roles of the two senses?

Answer 1

Vestibular apparatus is present in the inner ear. It maintains body balance during our day to day activities, including exercise.

We judge motion by comparing what the eyes see with what the vestibular organs sense about our body movement. If the vestibular apparatus says that we're not moving, then any movement sensed by the eyes must be outside the body. (The brain discounts the appearance of movement caused by eye movement itself.) Then the brain tells the eyes just how to move to keep track of the moving object. If we're moving and the world is moving, too, we need to keep track of the objects while adjusting for our body's movement. The eyes and the semicircular canals have to work together on this. However, if you twirl around and set the fluid of one or two pairs of the semicircular canals into motion and then stop suddenly, you fool the brain into thinking the world is spinning. The reason is that the vestibular fluid is moving as though you're moving, so the eyes are moved to track objects.This eye movement, called nystagmus, makes the world seem to spin. You can produce the same effect by drinking alcohol, which lowers the specific gravity of the fluid of the semicircular canals and stimulates the vestibular hair cells as though you're moving. Again the world spins. OR you can squirt ice water into the ear canal to produce convection in the semicircular canals.

This produces a very powerful spinning sensation, a vigorous nystagmus, and--frequently--vomiting. We did this when I was a lab instructor in a medical school neuroscience course as a grad student. You have to keep a bowl near the poor medical student's mouth. (Remember that the med student was a volunteer. I volunteered once for an anoxia experiment in physiology class and learned what sudden loss of consiousness is like. Brighter students know better than to volunteer.

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