• Transduce signals into electrical signals
• Allow for rapid response

3 TYPES

1) Ligand-gated Ion Channels

• Specific ligand is required for each channel
• Ligand binds to ligand binding site on channel
• Channel opens allowing ions to pass through
• When ligand dissociates, channel closes

2) Mechanically-gated Ion Channels

• Physical (i.e., stretching) forces on the membrane or channels are what open the channels and allow the ions to traverse the membrane

3) Voltage-gated Ion Channels

Sodium & Potassium Channels

a) Sodium Channel

• Change in membrane potential opens the channel – activation gates change to the open conformation and sodium can traverse the membrane
• Channel becomes inactivated – Inactivation gate “plugs” the channel and sodium cannot travel through the membrane
• Channel eventually resets back to closed conformation

b) Potassium channel

• Change in membrane potential opens the channel – activation gates change to the open conformation and potassium can traverse the membrane
• Channel eventually resets back to closed conformation