Getting to the HEART of the matter: How does the Sinoatrial Node work?

Question

* Why is it that an impulse from your "Sinoatrial Node" doesn't result in a contraction of your Atria and Ventricles at the same time? What would happen if this is what it did?

Answer 1

The Sino Atrial node or pacemaker is located in the right atrium of the heart. It initiates the impulse for contraction of the heart.

The impulse generated in the SA node causes the atria to contract simultaneously pumping blood into the ventricles.

The impulse is passed to the Atrio ventricular (AV) node which passes the impulse through a series of nerves called the Bundle of His. The impulse then pases up over the muscles of the ventricles via fibres called Purkinje fibres. This causes the ventricles to contract to pump blood into the pulmonary artery (Right ventricle) and the aorta (left ventricles)

The purpose of this is so that the ventricles do not contract until they are filled will blood from contraction of the atria.

Hope this helps!

Answer 2

In very simple terms the electrical impulse is directed within the nerve, which is 'insulated',  to specific muscles - those of the ventricles.

If both ventricles and atria contracted at the same time the heart would not function as a pump. When the atria contract where would the blood go - not into the ventricles because they are contracted as well.

More info here - http://en.wikipedia.org/wiki/Sinoatrial_...