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
   • An interneuron
   • A sensory neuron
   • 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 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
   • Y is a sensory neuron that brings the message in from the skin
5. 3.

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

   • 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
   • The reflex path stays in the spinal cord, and the brain is told afterward
6. 4.

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

   • Neurotransmitter chemicals released by neuron 1
   • Pieces of the cell body of 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?

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

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?

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

    Noah rides a bike uphill. Which pairing matches what two parts of the brain do on the ride?

    • Brainstem helps with balance; cerebellum keeps breathing going
    • Cerebellum helps with balance; brainstem keeps breathing going
    • Cerebellum helps with balance; brainstem stores memories of the route
    • Cerebellum plans the route and helps with balance; brainstem keeps breathing going
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 spinal cord, with no help from the brain
    • The brainstem, which helps keep breathing going
    • The cerebellum, the little brain that does the thinking
    • The cerebrum, because breathing needs a decision each time
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 were lowest while cycling
    • Both rates rose, and the cerebellum helps set both
    • Breathing rate rose, but heart rate stayed the same
    • Both rates rose from asleep to cycling, and the brainstem helps set both