Activity 3
3-1: Explain why the threshold voltage is not always the same value) between axons and within an axon)
Activity 31. Each region of the neuron contains distinct membrane proteins that provide the basis for the threshold differences.
2. The action potential is regenerated by the influx of sodium which establishes local currents that depolarize adjacent sections of the membrane to threshold. The action potential must be regenerated at adjacent sections of the membrane.
3. The action potential is not graded. It is “all or none,” so the peak value of the action potential doesn't change.
Activity 41. The sodium channels are voltage-gated sodium channels. Closure of the inactivation gate is a delayed response to the initial depolarization to threshold which closes the inactivation gate about 1 msec after sodium channels open.
2. Careful preparation of the pufferfish requires removal of the toxic portions that contain
tetrodotoxin. The poison is most concentrated in the liver, ovaries and skin of the fish.
3. Calcium channels could possibly substitute for sodium channels to provide an influx of cation.
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