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Blinkers: Is Blinking a Reflex Action?

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Author: Janice VanCleave

Problem: Is blinking a reflex action (an action that does not require thinking)?

Materials

  • helper
  • 1 sheet of transparent plastic wrap
  • 10 cotton balls

Procedure

Note: Do not substitute materials. It would be unsafe to use anything other than cotton balls.

  1. Have your helper hold the transparent plastic wrap in front of his or her face.
  2. Stand about 1 yard (1 meter) away from your helper.
  3. Without warning, throw a cotton ball directly at your helper's face. The cotton ball will be stopped by the plastic wrap.
  4. Continue throwing the cotton balls, one at a time, at your helper's face.
  5. Observe and record when the thrown cotton balls cause your helper to blink.

Results

Your helper will be more likely to blink when the first few cotton balls are thrown. After that, he or she may be able to concentrate on keeping the eyes open and, thus, not blink after getting used to the approaching balls.

Why?

Reflex action, such as blinking, is an automatic action that does not require thinking, and it takes concentration to try to inhibit (keep from happening) the involuntary action. Some people can better control the blinking response if they are aware that the stimuli (anything that causes a response-the thrown cotton balls in this experiment) are coming. If a sudden unexpected object approaches, the eyelids of all creatures will blink automatically. This involuntary movement is due to sensory cells in the eye sending a message to a central control center in the spine. From the spine, the instructions to close the eyes for protection are immediately relayed to the eye muscles resulting in the blinking action.

Blinkers

Let's Explore

Would the reflex response be affected if the cotton balls came unexpectedly from different directions? Determine this by repeating the experiment, but have two people throw cotton balls at odd times from different directions at a person shielding his or her face with a plastic sheet. Science Fair Hint: Photographs of this experiment can be used as part of a project display, along with a summary of the results.

Show Time!

Blinkers

  1. The hair in a cat's ears can detect the slightest air movement. This allows the cat to respond to movements that are even too slight to produce sounds or to catch its eye. Test the sensitivity of human hair by asking a helper to look away as you gently move your hand back and forth against the ends of hairs on your helper's head and arm (but without moving the hair). Did your helper feel the movements?
  2. Do organisms other than mammals have reflex actions? Earthworms do not have obvious sense organs, such as a nose or eyes, but they do have a nervous system that responds to stimuli such as touch or odors. Place several worms on a moist paper towel, and record their response to being touched with the end of a string. Photographs along with a summation of the responses can be displayed. (Note: Approval for using living organisms in your science fair project may be needed. Check with your teacher before beginning this experiment. Upon completion of the experiment return the worms to their natural environment.)
  3. What are some other common reflex actions in humans? You can display diagrams showing reflex actions that happen as a result of:
    • being startled
    • tapping the soft spot on your knee, below the kneecap
    • touching something sharp, like a tack

Blinkers

Check it Out!

Reflex action causes animals to jerk away from heat before actually feeling the pain. Find out about the protective short-circuit path taken by nerve impulses that produces a reflex act. A diagram along with your explanation of the movement of the nerve impulses can be displayed.

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