Action potentials and saltatory conductionEdexcel International A Level Biology: Mind map

Exam questions on Action potentials and saltatory conduction

1. A neuroscientist stimulates an axon in a laboratory and records the potential difference across its membrane. At rest the inside of the axon is at −70 mV relative to the outside. After a stimulus the potential difference rises rapidly to +40 mV and then falls back to −70 mV.
   Explain why the inside of the axon is negative relative to the outside at rest.2 marks
2. Tetrodotoxin (TTX), a poison found in pufferfish, blocks the voltage-gated sodium ion channels in axon membranes. A different laboratory chemical blocks only the voltage-gated potassium ion channels.
   Explain why a person poisoned with TTX becomes paralysed.2 marks
3. Two axons of the same diameter and 0.50 m long are compared. Axon A is myelinated and conducts impulses at 50 m s⁻¹. Axon B is unmyelinated and conducts impulses at 1.0 m s⁻¹.
   Explain why axon A conducts impulses faster than axon B.3 marks