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KNEE-JERK REFLEX

Test your friends reflexes with the knee-reflex test

Suitable For

Grade 3

Difficulty

1

Time Required

 <1 Hour

Supervision

Advised

What’s it about?

To have ‘reflexes’ is one of the most important and valuable characteristics a living organism can possess. A reflex is a quick reaction to a certain stimulus that a living organism’s body might perceive as dangerous. Reflexes are involuntary and we have no control over it. For example, if you would touch something that is very hot, you will pull your hand away very fast without even thinking about it.

A reflex is thus our bodies’ way to protect us against possible dangers that we might not even be aware of. A familiar reflex movement that is easy to study is the knee-reflex test:

Topics covered

Reflex, Knee-jerk reaction

What will I need?

  • CHAIR
  • PLASTIC RULER
  • A FRIEND

Procedure (Method)

Unfortunately, this section is only available in the e-book version of the project.

How does it work?

Unfortunately, this section is only available in the e-book version of the project.

The knee-jerk reflex happens because of the hand or ruler changing the shape of a muscle when the tendon is hit. When the hand or ruler hits the tendon at the knee, it stretches a muscle in the front of your friend’s thigh and stimulates the stretch receptors and a message is sent to the muscles of his / her thigh. The muscles in the front of the thigh contract and relax at the back causing your friend’s foot to jerk.

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