神经元兴奋性 Class 1 Neural Excitability Class 2 Neural Excitability f40, CI lass 1 excitability 仝 Class 2 excitability 250 g200 30 g F-I curve g20 F-I curve 100 200 300 500 1000 1500 jected dc-current, I(pA) injected dc-current, I(pA)神经元兴奋性