From: http://www.answers.com/topic/channelopathy

"Cells of the body, including nerve and muscle cells, are surrounded by thin coverings called membranes. Embedded in these membranes are a large and varied set of proteins that control the movement of materials across the membrane, in and out of the cell. One major type of material that crosses through such proteins are called ions, and the proteins that transport them are called ion channels.

Ions perform many different functions in cells. In neurons (nerve cells), they help transmit the electrical messages that allow neurons to communicate with each other, and with muscle cells. In muscle cells, they allow the muscle to contract. When the ion channels are defective, these activities may be disrupted."

<Think of ion channels as the port holes in a great ocean liner and pretend they are the only way to pass stuff onto or off of the ship. Suppose you are going to load a shipment of beach balls 18"in diameter through ports that the ship specs say are 19" in diam. No problem. But you find that due to a mutation that the ports are actually 17" in diam. That is a channelopathy. You may still be able to squeeze the beach balls through the port, but it will be slower, some will be damaged, etc. Things won't work right.>