Electrical System of the Heart - Topic Overview
What controls the timing of your heartbeat?
Your heart's electrical system controls the timing of your
heartbeat by regulating your:
- Heart rate, which is the number of times your
heart beats per minute.
- Heart rhythm, which is the synchronized
pumping action of your four heart chambers.
Your heart's electrical system should maintain:
- A steady heart rate of 60 to 100 beats per
minute at rest. The heart's electrical system also increases this rate to meet
your body's needs during physical activity and lowers it during
- An orderly contraction of your atria and ventricles (this is
called a sinus rhythm).
See a picture of the
heart and its electrical system .
How does the heart's electrical system work?
Your heart muscle is made of tiny
cells. Your heart's electrical system controls the timing of your heartbeat by
sending an electrical signal through these cells.
Two different types of cells in your heart enable the electrical
signal to control your heartbeat:
- Conducting cells carry your heart's electrical
- Muscle cells enable your heart's chambers to contract, an
action triggered by your heart's electrical signal.
The electrical signal travels through the network of conducting
cell "pathways," which stimulates your upper chambers (atria) and lower
chambers (ventricles) to contract. The signal is able to travel along these
pathways by means of a complex reaction that allows each cell to activate one
next to it, stimulating it to "pass along" the electrical signal in an orderly
manner. As cell after cell rapidly transmits the electrical charge, the entire
heart contracts in one coordinated motion, creating a heartbeat.
The electrical signal starts in a group of cells at the top of your
heart called the sinoatrial (SA) node. The signal then travels down through
your heart, triggering first your two atria and then your two ventricles. In a
healthy heart, the signal travels very quickly through the heart, allowing the
chambers to contract in a smooth, orderly fashion.
The heartbeat happens as
- The SA node (called the pacemaker of the heart) sends out an
- The upper heart chambers (atria) contract.
- The AV node sends an impulse into the ventricles.
lower heart chambers (ventricles) contract or pump.
- The SA node
sends another signal to the atria to contract, which starts the cycle over
This cycle of an electrical signal followed by a contraction is one