The breathing and nervous systems, and how a signal reaches the brain

Grade 7 Science Worksheet

Circle the best answer.

1. Read this first

   Levels ladder, not to scale

   Four steps from the smallest piece at the bottom to the biggest group at the top. Part | letter | job: cell | W | the smallest unit of life; tissue | X | a group of similar cells that do one job; organ | Y | several tissues working together as one body part; organ system | Z | several organs working together on a big job.

2. 1.

   A lung is made of several kinds of tissue that work together to move air and let oxygen pass. Luz places the lung on a levels ladder. Which level is it?

   • An organ, because it joins several tissues
   • A cell, because it holds the tiny air sacs
   • A tissue, because it is made of cells
   • An organ system, because it takes in air
3. 2.

   Milo reads that many nerve cells of one kind sit together and carry signals, but are not yet a whole body part. Which level is this group?

   • A cell, because each one is a nerve cell
   • An organ, because it carries signals for the body
   • A tissue, because similar cells work together
   • An organ system, because it joins many cells
4. 3.

   “Breathing drawing, not to scale:” Before a choir song, Pia breathes in. Air reaches the alveoli. What happens to the oxygen there?

   • It moves on down a tube into the stomach
   • It passes into the capillaries and is carried to body cells
   • It is made there from the carbon dioxide that arrives
   • It is used up in the air sacs, so no oxygen is breathed out

5. Breathing drawing, not to scale

   a chest outline with the air path inside. Letters: Y is the lungs. Numbered path: 1 nose or mouth, 2 trachea, 3 bronchi, 4 lungs, 5 alveoli. Air-mix card: air breathed in is about 21% oxygen.

6. 4.

   Ren sings in choir and breathes in and out. Air breathed in is about 21% oxygen. Which statement compares it with the air breathed out?

   • Breathed-out air has more oxygen, because the lungs make extra
   • Breathed-in air is oxygen, and breathed-out air is carbon dioxide
   • Breathed-out air has less oxygen and more carbon dioxide
   • Both are the same mix, because the lungs just move air around
7. 5.

   “Breathing drawing, not to scale” Tala sings a long note and then takes a quick breath in. Which action pulls air into the lungs?

   • The diaphragm contracts and makes more room in the chest
   • The air sacs make fresh oxygen that fills the lungs
   • The lungs squeeze themselves and pull air in
   • The windpipe pumps air down toward the stomach
8. 6.

   “Nervous-system drawing, not to scale: a body outline with the signal path inside. Parts shown:” Zee sees a ball coming. Which path carries the signal from the eye to the arm muscles?

   • receptor → motor nerve → brain → sensory nerve → muscle
   • receptor → sensory nerve → muscle → motor nerve → brain
   • receptor → sensory nerve → brain → sensory nerve → muscle
   • receptor → sensory nerve → brain → motor nerve → muscle
9. 7.

   “Nervous-system drawing, not to scale:” In a ball catch, a motor nerve reaches Ari’s arm muscle. In which direction does a signal travel along that motor nerve?

   • From the eye toward the brain, as the receptor sends it
   • From the muscle toward the brain, like a sensory nerve
   • Back and forth, bouncing between brain and muscle
   • From the brain out toward the muscle
10. 8.

    Nervous-system drawing, not to scale: a body outline with the signal path inside. Esme touches an icy window and pulls a hand back before thinking. Why can a reflex be faster than a choice made in the brain?

    • The receptor reaches straight into the muscle, so no nerve is needed
    • The brain sends a stronger, faster signal for a reflex than for a choice
    • The signal turns around in the spinal cord and does not wait for a decision
    • The muscle moves on its own, so no nerve signal has to travel
11. 9.

    “not to scale” After Jun pulls a hand back from an icy window, Jun’s brain learns what happened. How does the brain find out?

    • The brain is not told, because the spinal cord handles the signal alone
    • Another signal travels up the spinal cord, so the brain learns after the move
    • The motor nerve carries a report back from the muscle to the brain
    • The brain sent the signal that moved the hand, so it already knew about it
12. 10.

    Kira compares two actions: pulling a hand back from an icy window, and choosing which window to touch. What is different about the brain’s job?

    • The choosing skips the brain’s decision, but the pull-back needs it
    • The pull-back skips the brain’s decision, but the choosing needs it
    • Both wait for the brain to decide before the muscle moves
    • Both skip the brain, because the muscles do the work