ABSTRACT
Neurons are excitable because they have voltage-dependent ion channels in their plasma membrane. These transmembrane proteins have two properties, ion selectivity and voltage sensitivity. Voltage-dependent channels are classified according to the ion (Na+, K+ or Ca2+) to which they are preferentially permeable. A large number have been identified to date. They are multi-subunit complexes. The ion channel a subunit(s) are accompanied by a variety of β subunits which modify the channel properties.
