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

   The nose, windpipe, bronchi and lungs work together to bring in oxygen. Noah adds this whole group to the levels ladder. Which level is it?

   • An organ system, because several organs work together
   • An organ, because it is one large body part
   • A tissue, because it is made of cells
   • A cell, because living things have cells
5. 4.

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

6. 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.

7. 5.

   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-in air is oxygen, and breathed-out air is carbon dioxide
   • Breathed-out air has more oxygen, because the lungs make extra
   • Both are the same mix, because the lungs just move air around
   • Breathed-out air has less oxygen and more carbon dioxide
8. 6.

   “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 windpipe pumps air down toward the stomach
   • The lungs squeeze themselves and pull air in
   • The air sacs make fresh oxygen that fills the lungs
   • The diaphragm contracts and makes more room in the chest
9. 7.

   “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 → sensory nerve → brain → sensory nerve → muscle
   • receptor → sensory nerve → brain → motor nerve → muscle
   • receptor → sensory nerve → muscle → motor nerve → brain
   • receptor → motor nerve → brain → sensory nerve → muscle

10. Use this

    Nervous-system drawing, not to scale: a body outline with the signal path inside. Parts shown: receptor, sensory nerve, spinal cord, brain, motor nerve. The receptor is in the skin of the fingertip.

11. 8.

    Bo touches a cold window and notices the chill. Which path carries that message from the skin to the brain?

    • receptor in the skin → sensory nerve → brain → spinal cord
    • receptor in the skin → sensory nerve → spinal cord → brain
    • brain → spinal cord → sensory nerve → receptor in the skin
    • receptor in the skin → motor nerve → spinal cord → brain
12. 9.

    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 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 receptor reaches straight into the muscle, so no nerve is needed
    • The muscle moves on its own, so no nerve signal has to travel
13. 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?

    • Both skip the brain, because the muscles do the work
    • Both wait for the brain to decide before the muscle moves
    • 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