Potentials

• C= Q/V
• C~ area/thickness
• C_m= 1uF/cm²= 0.01pF/um²

• Q=CV..
• Q/t=I=C(V/t)

I=gV or I=g(V-Vrest)

T= RmCm

so if more channels-> inc g-> dec R-> dec T= less time of voltage transient (faster)

• Dec C by inc thickness. (10 fold)
• 1. fewer charges need to change V
• 2. voltage transient is faster (T-RC)

• []out/[]in: 5:140 (1:28)
• Nernst: -84

• []out/[]in: 145:5-15 (~15:1)
• Nerst: +68

• []out/[]in: 110:4-3 (~10:1)
• Nerst: -58

• []out/[]in: 1-2:0.0001 (10,000:1)
• Nerst: +116

Reduced excitability after AP

• Absolute: no matter how large I, must wait
• Relative: during which a larger current or duration can stimulate

• Dramatic inc in g, conductance (40X) produces AP... explaine high g_Na during AP
• During AP, Na follows Nernst trace.
• AP: 20 to 40 mV, 3-4ms