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| September/October, 2005 Volume 11, Issue 5 |
Pen Pal Listing
Support Group Listing
Q&A With Phillip Watkins, MD
Director of the MVP Center, Alabama
Subscribers Page
Notice of seminars and support group meetings.
| The Heart and Central Nervous System
The Autonomic nervous system (ANS) is the devision of the nervous system that regulates our visceral functions, such as heartbeat and gland activity. It is also known as the involuntary nervous system since it is not under our control, as we cannot decide how fast or slow our heartbeat is or how much acid our stomach should secrete.
The ANS is organized into two parts, the sympathetic and parasympathetic, which bring about opposite effects on the same organ. For example, the sympathetic increases the strength of the heart contraction, while the parasympathetic decreases the heart contraction. The sympathetic constricts the blood vessels, while the parasympathetic dilates them.
How does the ANS control the heartbeat? When at rest the normal heartbeat is anywhere from 60-100 beats per minte. During sleep it goes down to 50-60 beats per minute, and it accelerates to above 100 with emotional excitement.
Increased heart rate is produced by increased sympathetic activity.
During sleep the parasympathetic is in control, and the sympathetic is suppressed so that the heart rate becomes lower. In times of fear the sympathetic takes command, and the parasympathetic is suppressed so the heart rate becomes faster.
The parasympathetic nerves originate from the Medulla in the brain, and specifically from the Nucleus Ambigous. The nerve which carries those fibers, is called the Vagus.
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Headlines from past issues:
You are not going to have a heart attack
The autonomic nervous system
How I live with MVPS
Oh, those "flutters" and "skipped" beats
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Comments about our newsletter:
Dr. Hartman, cardiologist at Good Samaritan Hosiptal in Illinois
"Your newseletter is full of good information. We need people like you."
Debra Doud, MD, cardiologist, Naperville, IL
The Durantes have done a wonderful job of helping people with this syndrome"
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The vagus nerve innervates the Sinus node and the AV node. The vagus therefore, can slow the heartbeat by inhibiting the activity of the Sinus node, which is the main switch of the heartbeat. If the vagus activity is very high, it may even cease the activity of the sinus node and cause complete cessation of the heartbeat for seconds.
The parasympathetic activity dominates the sympathetic activity at the Sinus node, i.e. when the Sinus node is subjected to combined parasympathetic and sympathetic stimulation the heartbeat slows under the influence of the parasympathetic.
The AV node is located at the junction between the atria (upper cardiac chambers). Hence the name Atrio-Ventricular node. It
enables the transmission of the eletric impulse from the atria to the ventricles. The Vagus nerve results in delay of this transmission.
The sympathetic pathways originate from the spinal cord and travel over the great heart vessels to reach the heart. Upon reaching the heart they are distributed over the heart chambers like an extensive net. Accompaning the coronary arteries, they penetrate the heart muscle (myocardium).
The effects of the sympathetic diminish gradually after cessation of stimulation, while the effects of the parasympathetic diminish abruptly after cessation of stimulation. For example, in a freightening situation it takes longer time for your heartbeat to go back to normal even after the danger is over. while your heartbeat briskly increases as you wake up, here the parasympathetic, which is dominat during sleep, abruptly gives way.
| Many people born with a prolapsed mitral vavle may also have a slight imbalance of the central nervous syste, this is why we feel heart palpitations and tachycardia at inappropriate times. An example would be waking up in the middle of the night with your heart pounding. Our parasympathetic system is supposed to be active, but because of the imbalance our sympathetic is activated.
Functions of the ANS
The Sympathetic
Speeds Heart Rate
Vasoconstricts
Dilates pupils
Slows Digestion
Induces Wakefulness
The Parasympathetic
Slows Heart Rate
Vasodilates
Constricts Pupils
Induces Sleep
The nervous system maintains a delicate balance of the body. There are many ways that this system can become out of balance, resulting in dysautonomia. The sympathetic can be too active while the parasympathetic is not active enough, resulting in an inappropriate response of the ANS. Also both systems can be too active or underactive. The pattern of dysautonomia can also change overtime.
Remember, most if not all of the symptoms of MVPS are a result of "dysautonomia."
Page 2, Pen Pal List, Medication Corner, Endocarditis
Page 3, Subscriber's Page
Page 4, Q&A, with Dr. Watkins, White-coat Hypertension
Page 5, Support Groups and Resources
Page 6, Sugar-Free Recipe
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