Nerve impulses Quiz
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5 questions, one answer each
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1. What is the main reason the resting potential is negative inside the axon?
- A. Na⁺ diffuse in rapidly
- B. The membrane is impermeable to all ions
- C. More K⁺ diffuse out than Na⁺ diffuse in, and the pump moves 3 Na⁺ out for 2 K⁺ in
- D. Chloride ions are pumped in
2. What opens at threshold to cause depolarisation?
- A. Voltage-gated potassium channels
- B. Stretch-mediated channels
- C. Calcium pumps
- D. Voltage-gated sodium ion channels
3. A stimulus of twice the strength produces which change in the axon?
- A. An action potential twice the size
- B. An action potential of the same size, possibly at a higher frequency
- C. No action potential
- D. A larger resting potential
4. A refractory period of 4.0 ms means the maximum frequency is:
- A. 250 per second
- B. 25 per second
- C. 400 per second
- D. 4 per second
5. Why does a myelinated axon conduct faster than a non-myelinated axon of the same diameter?
- A. Myelin makes sodium ions diffuse faster
- B. There are more sodium channels along the axon
- C. Action potentials jump between nodes of Ranvier, so fewer depolarisations are needed
- D. Myelin removes the refractory period