I) Channels With Quatrameric Structure Related to
   Voltage-Gated, Cation-Permeant Channels:
   A) Voltage-gated:
     •K+ permeant
     •Na+ permeant
     •Ca++ permeant
     •Cation non-specific permeant (HCN)
   B) Cyclic Nucleotide-Gated (Cation non-specific
     permeant)
   C) TRP Family (Cation Non-specific); Gated by:
       • osmolarity
     • pH
     • mechanical force
     • ligand binding
     • temperature