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Unit 19: Biology Part 2 Page 96 of 137

8. Evaluate the accuracy of your hypothesis. Are you surprised?

Experiment: The Heart – A Special Muscle

1. Make a fist with your hand. This is about the size of your heart.

2. Begin to slightly open and close your hand, as though your “heart” is
beating.
3. Measure how long it takes before your hand hurts
4. Your heart beats 24 hours a day. But it only hurts when a person is
having a heart attack. How can this be?

Answer: Your muscles need oxygen. When a muscle like your hand does not
get enough oxygen, it still makes the motion, but it uses a different method
of getting energy that produces lactic acid, which causes the pain. The heart
is constantly supplied with oxygen from coronary circulation. So, lactic acid
is never needed.

Experiment: A Tennis Ball Heart

Materials:

 1 tennis ball
 Water
 Scissors or knife

1. Carefully cut a hole in the tennis ball
2. Fill the ball with water
3. Squeeze the ball, then release it. What do you observe?
4. How is the ball similar to our heart, as it pumps blood? What does
your hand’s squeeze represent?

Experiment: Observing Your Capillaries

Materials:

 Cedarwood furniture oil
 Flashlight

1. Soak your finger in cedarwood furniture oil.
2. Shine a strong flashlight on your finger

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