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Heart Disease (Expert Forum)
Re: the sino-atrial node
This forum is for questions and support regarding heart issues such as: Angina, Angioplasty, Arrhythmia, Bypass Surgery, Cardiomyopathy, Coronary Artery Disease, Defibrillator, Heart Attack, Heart Disease, High Blood Pressure, Mitral Valve Prolapse, Pacemaker, PAD, Stenosis, Stress Tests.
Re: the sino-atrial node
by CCF Cardio MD - MTR, Jan 01, 1995 12:00AM
Posted By CCF CARDIO MD - MTR on November 21, 1998 at 10:07:00:
In Reply to: the sino-atrial node posted by marit on November 20, 1998 at 04:44:19:
Hi my name is Marit and I have to do a report on the heart. I'd like to know how the electric activity in the sino-atrial node starts? I know the message comes from the brain, but what kind message is it? A hormon? An impuls? I thank you in advance.
Marit
Dear Marit, thank you for your question. The SA node is innervated by the vagus nerve which is part of the autonomic nervous system. The vagus nerve signals the SA node to increase or decrease its firing (which corresponds directly to the heart rate) in response to stress, situations, etc. For example, if you are suddenly frightened, the sympathetic nervous system causes you to suddenly be hyperalert, your heart rate to increase, sweating, and your senses to sharpen. The SA node cells have a property called automaticity which means that they can generate their own electrical impulses. Thus, the SA node is constantly firing impulses which cause the ventricles to become excited and contract. Ventricular contraction ejects blood from the heart to the rest of the body (heartbeat). Even if the neural connections between the brain and the heart are severed, the SA node will continue to fire regularly. However, the SA node will not continue to respond to signals from the brain to increase or decrease its activity.
I hope you find this information useful. Information provided in the heart forum is for general purposes only. Only your physician can provide specific diagnoses and therapies. Please feel free to write back with additional questions. Good luck!
If you would like to make an appointment at the Cleveland Clinic Heart Center, please call 1-800-CCF-CARE or inquire online by using the Heart Center website at www.ccf.org/heartcenter. The Heart Center website contains a directory of the cardiology staff that can be used to select the physician best suited to address your cardiac problem.
In Reply to: the sino-atrial node posted by marit on November 20, 1998 at 04:44:19:
Hi my name is Marit and I have to do a report on the heart. I'd like to know how the electric activity in the sino-atrial node starts? I know the message comes from the brain, but what kind message is it? A hormon? An impuls? I thank you in advance.
Marit
Dear Marit, thank you for your question. The SA node is innervated by the vagus nerve which is part of the autonomic nervous system. The vagus nerve signals the SA node to increase or decrease its firing (which corresponds directly to the heart rate) in response to stress, situations, etc. For example, if you are suddenly frightened, the sympathetic nervous system causes you to suddenly be hyperalert, your heart rate to increase, sweating, and your senses to sharpen. The SA node cells have a property called automaticity which means that they can generate their own electrical impulses. Thus, the SA node is constantly firing impulses which cause the ventricles to become excited and contract. Ventricular contraction ejects blood from the heart to the rest of the body (heartbeat). Even if the neural connections between the brain and the heart are severed, the SA node will continue to fire regularly. However, the SA node will not continue to respond to signals from the brain to increase or decrease its activity.
I hope you find this information useful. Information provided in the heart forum is for general purposes only. Only your physician can provide specific diagnoses and therapies. Please feel free to write back with additional questions. Good luck!
If you would like to make an appointment at the Cleveland Clinic Heart Center, please call 1-800-CCF-CARE or inquire online by using the Heart Center website at www.ccf.org/heartcenter. The Heart Center website contains a directory of the cardiology staff that can be used to select the physician best suited to address your cardiac problem.
