Which node initiates the heartbeat

In a healthy heart, the signal travels very quickly through the heart, allowing the chambers to contract in a smooth, orderly fashion. This cycle of an electrical signal followed by a contraction is one heartbeat.

When the SA node sends an electrical impulse, it triggers the following process:. After the electrical signal has caused your atria to contract and pump blood into your ventricles, the electrical signal arrives at a group of cells at the bottom of the right atrium called the atrioventricular node, or AV node.

The AV node briefly slows down the electrical signal, giving the ventricles time to receive the blood from the atria. The electrical signal then moves on to trigger your ventricles. When the electrical signal leaves the AV node, it triggers the following process:. After your atria and ventricles contract, each part of the system electrically resets itself. The cells of the SA node at the top of the heart are known as the pacemaker of the heart because the rate at which these cells send out electrical signals determines the rate at which the entire heart beats heart rate.

The normal heart rate at rest ranges between 60 and beats per minute. Your heart rate can adjust higher or lower to meet your body's needs. Your brain and other parts of your body send signals to stimulate your heart to beat either at a faster or a slower rate.

Although the way all of the chemical signals interact to affect your heart rate is complex, the net result is that these signals tell the SA node to fire charges at either a faster or slower pace, resulting in a faster or a slower heart rate.

For example, during periods of exercise, when the body requires more oxygen to function, signals from your body cause your heart rate to increase significantly to deliver more blood and therefore more oxygen to the body. Your heart rate can increase beyond beats per minute to meet your body's increased needs during physical exertion.

Similarly, during periods of rest or sleep, when the body needs less oxygen, the heart rate decreases. Some athletes actually may have normal heart rates well below 60 because their hearts are very efficient and don't need to beat as fast. Changes in your heart rate, therefore, are a normal part of your heart's effort to meet the needs of your body. Sympathetic and parasympathetic nervous systems.

The sympathetic and parasympathetic nervous systems are opposing forces that affect your heart rate. Both systems are made up of very tiny nerves that travel from the brain or spinal cord to your heart.

The sympathetic nervous system is triggered during stress or a need for increased cardiac output and sends signals to your heart to increase its rate. The parasympathetic system is active during periods of rest and sends signals to your heart to decrease its rate. During stress or a need for increased cardiac output, the adrenal glands release a hormone called norepinephrine into the bloodstream at the same time that the sympathetic nervous system is also triggered to increase your heart rate.

This hormone causes the heart to beat faster, and unlike the sympathetic nervous system that sends an instantaneous and short-lived signal, norepinephrine released into the bloodstream increases the heart rate for several minutes or more.

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Xylem Transport 2. Some athletes actually may have normal heart rates well below 60 because their hearts are very efficient and don't need to beat as fast. Changes in your heart rate, therefore, are a normal part of your heart's effort to meet the needs of your body. The sympathetic and parasympathetic nervous systems are opposing forces that affect your heart rate.

Both systems are made up of very tiny nerves that travel from the brain or spinal cord to your heart. The sympathetic nervous system is triggered during stress or a need for increased cardiac output and sends signals to your heart to increase its rate.

The parasympathetic system is active during periods of rest and sends signals to your heart to decrease its rate. During stress or a need for increased cardiac output, the adrenal glands release a hormone called norepinephrine into the bloodstream at the same time that the sympathetic nervous system is also triggered to increase your heart rate.

This hormone causes the heart to beat faster, and unlike the sympathetic nervous system that sends an instantaneous and short-lived signal, norepinephrine released into the bloodstream increases the heart rate for several minutes or more. Author: Healthwise Staff. Medical Review: Rakesh K.

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You are here Home » Electrical System of the Heart. Top of the page. 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 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 sleep. An orderly contraction of your atria and ventricles this is called a sinus rhythm.