Why does cardiac muscle have many gap junctions?

1 Answer
Sep 19, 2015

Cardiac cells have many gap junctions so that the ions responsible for causing the heartbeat can easily flow through all of the heart.


The heart has an area in the right atrium called the sinoatrial node where specialized cells can begin their own stimulation for the heartbeat. This stimulation is caused by a flood of Na+ ions into those cells and their subsequent travel to neighboring cells. This is called a wave of depolarization.

The wave of depolarization must rapidly spread through both atria first, causing their contraction, and then carry on to the Purkinje fibers to stimulate contraction of the ventricles.

Gap junctions allow the passage of the ions responsible for the depolarization. Where cardiac cell membranes meet they fold up into a rippled surface and this appears as a dark line called an intercalated disc when looking at muscle tissue under a microscope.

The rippled surface of the intercalated disc is full of many gap junctions, like little tunnels, that allow the speedy spread of the wave of depolarization from cell to cell.