Neurons and the main parts of the brain

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   “Reflex path (model, not to scale):” 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
   • A glial cell
   • An interneuron
2. 2.

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

   • The signal first runs backward from the muscle to the skin
   • The brain sends the move first, and the spinal cord copies it
   • The impulse jumps each gap electrically, so no chemicals slow it
   • The reflex path stays in the spinal cord, and the brain is told afterward
3. 3.

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

   • The same electrical impulse, jumping straight across
   • Pieces of the cell body of neuron 1
   • Neurotransmitter chemicals released by neuron 1
   • Myelin released by neuron 1
4. 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?

   • Both ways, from A to B and from B to A, at the same time
   • 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

5. Read this first

   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

6. 5.

   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
8. 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 brainstem, part Y, which stores the practice as a memory
   • The spinal cord, part Z, which keeps the notes in order
   • The cerebellum, part X
   • The cerebrum, part W, because it plans movements, so it also fixes them
9. 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
   • Cerebellum plans the route and helps with balance; brainstem keeps breathing going
   • Brainstem helps with balance; cerebellum keeps breathing going
   • Cerebellum helps with balance; brainstem keeps breathing going
10. 8.

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

    • 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
    • Axon B, wrapped in myelin, carries the impulse faster than axon A
11. 9.

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

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

12. 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

13. 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 rose from asleep to cycling, and the brainstem helps set both
    • Both rates rose, and the cerebellum helps set both
    • Both rates were lowest while cycling