Neurons and the main parts of the brain

Grade 9 Science Worksheet

Circle the best answer.

1. Read this first

   Use this

   Reflex path (model, not to scale):

3. 1.

   Ari brushes a hand against a prickly pinecone, and the hand pulls away. What kind of neuron is X, which links W to Y inside the spinal cord?

   • A motor neuron
   • A sensory neuron
   • An interneuron
   • A glial cell
4. 2.

   Bo reads the same reflex path. Which statement about neuron Y, which ends on the arm muscle, is right?

   Use the picture in question 1.

   • Y is a sensory neuron that brings the message in from the skin
   • Y is an interneuron that stays inside the spinal cord
   • Y is a motor neuron that carries the message from the muscle back to the cord
   • Y is a motor neuron that carries the message out to the muscle
5. 3.

   Esme brushes a hand against a prickly pinecone. The hand starts to pull away before Esme feels the prick. Why?

   • The reflex path stays in the spinal cord, and the brain is told afterward
   • The impulse jumps each gap electrically, so no chemicals slow it
   • The brain sends the move first, and the spinal cord copies it
   • The signal first runs backward from the muscle to the skin
6. 4.

   Jun studies a chemical synapse. What does the arrow marked ? carry across the gap?

   • Pieces of the cell body of neuron 1
   • Neurotransmitter chemicals released by neuron 1
   • Myelin released by neuron 1
   • The same electrical impulse, jumping straight across
7. 5.

   (model, not to scale). No arrow is drawn. Kira looks at a chemical synapse between neuron A and neuron B. Which way does the message cross?

   • Both ways, from A to B and from B to A, at the same time
   • From A's axon terminals to B's dendrites, and not back
   • From B's dendrites to A's axon terminals
   • From A's cell body straight to B's cell body

8. Synapse steps (model data)

   step	what happens
   1	An impulse travels down the axon of neuron 1 to its axon terminals
   2	?
   3	Receptors on neuron 2 pick up the message

9. 6.

   Luz reads the steps at a chemical synapse. What happens at step 2?

   • The terminals grow across the gap and join neuron 2
   • The electrical impulse leaps across the gap into neuron 2
   • Neurotransmitter flows back up the axon toward the cell body
   • Small sacs in the terminals release neurotransmitter into the gap
11. 7.

    Milo practices a short piece on the piano. The cerebrum plans the finger movements. Which part compares the plan with feedback from the hands and corrects the movement?

    • The cerebellum, part X
    • The spinal cord, part Z, which keeps the notes in order
    • The brainstem, part Y, which stores the practice as a memory
    • The cerebrum, part W, because it plans movements, so it also fixes them
12. 8.

    Pia is asleep, and breathing keeps going without any effort. Which part of the brain helps keep breathing going?

    Use the picture in question 7.

    • The brainstem, which helps keep breathing going
    • The spinal cord, with no help from the brain
    • The cerebrum, because breathing needs a decision each time
    • The cerebellum, the little brain that does the thinking
13. 9.

    Both axons have the same width. Ren reads a card about two axons. Which statement does the card support?

    • Axon B, wrapped in myelin, carries the impulse faster than axon A
    • Myelin makes the impulse stronger as it travels
    • The two axons carry the impulse at the same speed
    • Axon A is faster because it has no wrapping in the way

14. Model rate card (model data)

    activity	breathing rate (breaths per minute)	heart rate (beats per minute)
    Asleep	12	60
    Walking	18	90
    Cycling	30	130

15. 10.

    Zee reads a card of breathing and heart rates. Which statement does the card support?

    • Both rates rose, and the cerebellum helps set both
    • Breathing rate rose, but heart rate stayed the same
    • Both rates were lowest while cycling
    • Both rates rose from asleep to cycling, and the brainstem helps set both