Action potentials and saltatory conduction Quiz
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5 questions, one answer each
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1. Which ion movement causes depolarisation?
- A. K⁺ out of the axon
- B. Na⁺ into the axon
- C. Na⁺ out of the axon
- D. Cl⁻ into the axon
2. What is the main reason an action potential cannot travel backwards?
- A. The myelin sheath blocks it
- B. K⁺ channels are all open ahead
- C. The synapse prevents it
- D. The region behind is in its refractory period
3. What is the effect of myelination?
- A. It lowers the resting potential
- B. It increases the threshold
- C. It allows saltatory conduction, so impulses are conducted faster
- D. It removes the need for the sodium-potassium pump
4. A stimulus is below the threshold potential. What happens?
- A. A small action potential forms
- B. A larger action potential forms
- C. No action potential forms
- D. The axon hyperpolarises permanently
5. An impulse travels 0.40 m along a myelinated axon in 0.0080 s. What is its speed?
- A. 50 m s⁻¹
- B. 5.0 m s⁻¹
- C. 0.032 m s⁻¹
- D. 320 m s⁻¹