Hi! We are also doing human body now. Here are a few of our favorites:
Brain/Nerves: We test our reaction time. Have students pair up. One student holds a ruler about an inch above the other student's hand and then drops it without telling them when. See if the other student can catch it. Try about 5 times. Also for this we spend a little time looking at optical illusions and how sometimes our messages can get a little messed up. For instance say what color the following words are typed in not what the words say: red orange blue yellow purple green
Lungs/Heart: See if you can borrow a stethoscope from your school nurse. Listen to hearts before and after exercise. Test your lungs. Get a glass of water and straw. See how long students can blow bubbles without stopping. Have one partner time while one tests and then vice versa.
Bones: Read Dem Bones
We glue "bones" to construction paper made out of noodles and label. Use a shell for the cranium. Spiral noodles for the spine. Bow tie for pelvis. Penne for upper arm and thigh. Linguine for radius/ulna and tibia/fibula. Use a small marshmallow for patella. They turn out cute, but make sure to use liquid glue and lay flat to dry. It will stick just fine!
Digestion: This one is a little yucky, but gets the point across. Take two baggies and put a saltine cracker in each. In one baggie put a little water. Have each student shake. The one with the water or "saliva" will break down much quicker.
Good luck. I'm anxious to add new ideas too!