Neurons and the main parts of the brain
Grade 9 Science Worksheet
Circle the best answer.
“Reflex path (model, not to scale):” Bo reads the same reflex path. Which statement about neuron Y, which ends on the arm muscle, is right?
- 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
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 impulse jumps each gap electrically, so no chemicals slow it
- The brain sends the move first, and the spinal cord copies it
- The reflex path stays in the spinal cord, and the brain is told afterward
Jun studies a chemical synapse. What does the arrow marked ? carry across the gap?
- Pieces of the cell body of neuron 1
- The same electrical impulse, jumping straight across
- Neurotransmitter chemicals released by neuron 1
- Myelin released by neuron 1
(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
- 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
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 Luz reads the steps at a chemical synapse. What happens at step 2?
- The electrical impulse leaps across the gap into neuron 2
- Small sacs in the terminals release neurotransmitter into the gap
- Neurotransmitter flows back up the axon toward the cell body
- The terminals grow across the gap and join neuron 2
Noah rides a bike uphill. Which pairing matches what two parts of the brain do on the ride?
- 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
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 spinal cord, with no help from the brain
- The cerebellum, the little brain that does the thinking
- The brainstem, which helps keep breathing going
- The cerebrum, because breathing needs a decision each time
Both axons have the same width. Ren reads a card about two axons. Which statement does the card support?
- The two axons carry the impulse at the same speed
- Myelin makes the impulse stronger as it travels
- Axon A is faster because it has no wrapping in the way
- Axon B, wrapped in myelin, carries the impulse faster than axon A
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
- After the peak, the drop means the impulse runs back toward the dendrites
- The voltage starts at −70 mV, peaks at +30 mV, then returns to −70 mV
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 Zee reads a card of breathing and heart rates. Which statement does the card support?
- Both rates were lowest while cycling
- 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