Darkthorn’s Blog

- Tetrodoxin blocks Na+ channels, nifedipine blocks Ca2+ channels

- voltage gated channel family – membrane spanning protein with 4 subunits with 6 membrane spanning domains each.

- S4 senses membrane voltage, S2 forms conducting pore

- opening/closing regulated by membrane potential

- other ion channels – cation – cellular activity, ion channel properties, spontaneous transmitter release, not regenerative

- ? is the length of an axon, the distance at which the voltage declines to ~37% of the original value (exponential decay). It depends on the diameter, membrane leakiness (Rm) and cytoplasmic crowdedness (Ri)

- active – the action potential, maintains full size (all or nothing) but is slow

- passive – fast, but decays quickly

- combined by mylination – active at the nodes of ranvier, passive between

- Na+ channels abundant in axon hillock, nodes of ranvier & soma, least in axon beneath myelin & dendrites

- K+ channels wide spread

- Ca2+ channels abundant in terminals, dendrites & areas of soma