SA node

[Kailas]

How does SA node produce electric impulse?

[JackBean]

And are we supposed to guess what is SA node? Or ask the 8-ball?

[Darby]

Sino-atrial node in the heart, I'm pretty sure. I think it works like clusters of nerve cells do, even though I don't think they are technically nerve cells.

[jonjominns]

The SA node is a very complicated little piece of tissue located within the heart. Hence, the action of producing electrical impulses is equally as complex. I will try and explain the process as simply as I can. Electrical impulse in the SA node occurs because regular action potentials. There are a number of different phases to the process; firstly the depolarisation phase of the action potential takes place. This is then followed by the next phase of repolarisation. The cell repolarises between fully around -60mV, at this time the cycle is repeated. Membrane potential changes that occur during the cycle are brought about by the changes in movement of Calcium and Potassium ions (and to a lesser degree, Sodium) across the membrane through ion channels, which at different times open and close during the action potential. As a channel opens, an increase in electrical conductance of the specific ion occurs through the channel. Similarly, as the channel closes, electrical conductance decreases. As the ions (Na+, Ca++ and K+) travel through channels which are open, electrical current is generated which in turn changes the membrane potential.

That is as simply as I can put it, it is still quite complex but hope it is of help.