What's Happening?


Your Bones & Muscles

What made your muscles hurt or burn?

When muscles work hard and don't get enough oxygen, they continue to work without oxygen. The result is a burning feeling due to lactic acid build-up.

Did you know?

There are 650 muscles and about 206 bones in the human body, or about three muscles for every bone.


Your Heart & Circulation

Did your pulse beat change after you did the Jumping Jacks?

When muscles work they need oxygen.

Oxygen for the muscles is carried in the blood.

If the muscles work hard they need extra oxygen so the heart pumps blood a bit faster through the arteries and veins and to the muscles.

Did you know?

The heart is a powerful enough muscle to propel blood to all these places at a notably high speed and pressure.

The heart is an involuntary muscle. You can't contract it when you want like you can with your biceps. Hormones, however, can trigger it to pump faster or to relax.


Your Senses & Nervous System

The ruler will fall in less than 0.25 seconds. Your nervous system reacts quickly to catch the ruler before it falls.

How did your senses and nervous system work together to react?

Did you know?

Your nerves relay messages by electric impulses. Messages begin at the site of stimulus and move from one nerve to the next until they reach the brain. Your brain then decides what response to send back.

Something to Think About:

In this experiment, where is "the site of the stimulus" mentioned above?


Your Lungs & Respiratory System

Did the straw make it easier or harder to breathe?

The straw makes breathing more difficult because it limits the amount of air your mouth can take in. This creates an oxygen debt in your body.

Did you know?

You breathe in 1.5 gallons of air per minute. Imagine how much air the 6+ billion people in the world take in each minute! Plants are our lifesavers since they supply the air with the oxygen we need to live.


Your Digestive System

Did you taste the Saltine carefully?

The first half probably tasted salty, just like a Saltine cracker should!

What about the second half? The half that you sucked.
This time the Saltine may have begun to taste slightly sweet. Why?
Because - Your spit contains chemicals that break down the cracker into sugars that your taste buds can sense!

Did you know?

Your intestines are about 26 feet long, the length of about three cars! Five feet is large intestine, where water is reabsorbed. The rest is small intestine, where nutrients are absorbed.


Your Immune System

Did something grow on the surface of the potatoes?

You will find that microbes will have grown on both potatoes, even the one peeled with your washed hands.

If washing does not get rid of the microbes why don't you get sick from the microbes on your own hands?

Your immune system is always on the lookout! Thorough washing does get rid of some of the microbes. Any small number of malicious (bad for us) microbes remaining will be dealt with by your body's immune system.

Did you know?

  1. Some microbes in our bodies are actually beneficial (useful).

  2. Occasionally the immune system works against us by attacking our own cells or foreign cells we want to preserve, like an organ transplant for example.