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 glial cell
   • An interneuron
   • A sensory neuron
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 motor neuron that carries the message out to the muscle
   • 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 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.

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

7. 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

8. 5.

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

   • Neurotransmitter flows back up the axon toward the cell body
   • Small sacs in the terminals release neurotransmitter into the gap
   • The electrical impulse leaps across the gap into neuron 2
   • The terminals grow across the gap and join neuron 2
10. 6.

    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 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
    • The cerebellum, part X
11. 7.

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

    Use the picture in question 6.

    • Cerebellum helps with balance; brainstem stores memories of the route
    • Brainstem helps with balance; cerebellum keeps breathing going
    • Cerebellum helps with balance; brainstem keeps breathing going
    • 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 6.

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

    Tala reads a graph of a neuron's voltage during one impulse. Which statement does the graph support?

    • After the peak, the drop means the impulse runs back toward the dendrites
    • The voltage is highest at 2 ms, at the threshold
    • The voltage stays at −70 mV the whole time
    • The voltage starts at −70 mV, peaks at +30 mV, then returns to −70 mV

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?

    • 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
    • Both rates rose, and the cerebellum helps set both