The Vagus Nerve and The Heart
Parasympathetic innervation of the heart is controlled by the vagus nerve. To be specific, the vagus nerve acts to lower the heart rate. The right vagus innervates the sinoatrial node. Parasympathetic hyperstimulation predisposes those affected to bradyarrhythmias. The left vagus when hyperstimulated predisposes the heart to atrioventricular (AV) blocks.
At this location, neuroscientist Otto Loewi first proved that nerves secrete substances called neurotransmitters, which have effects on receptors in target tissues. In his experiment, Loewi electrically stimulated the vagus nerve of a frog heart, which slowed the heart. Then he took the fluid from the heart and transferred it to a second frog heart without a vagus nerve. The second heart slowed down without an electrical stimulation. Loewi described the substance released by the vagus nerve as vagusstoff, which was later found to be acetylcholine. Drugs that inhibit the muscarinic cholinergic receptor (anticholinergics) such as atropine and scopolamine are called vagolytic because they inhibit the action of the vagus nerve on the heart, gastrointestinal tract, and other organs. Anticholinergic drugs increase heart rate and are used to treat bradycardia (slow heart rate). Atropine is no longer indicated for the treatment of pulseless electrical activity (PEA) or asystole per the 2010 ACLS guidelines, as it has not been shown to improve outcomes in these clinical scenarios.
Read more about this topic: Vagus Nerve
Famous quotes containing the words nerve and/or heart:
“The American people is out to get the kaiser. We are bending every nerve and every energy towards that end; anybody who gets in the way of the great machine the energy and devotion of a hundred million patriots is building towards the stainless purpose of saving civilization from the Huns will be mashed like a fly. I’m surprised that a collegebred man like you hasn’t more sense. Don’t monkey with the buzzsaw.”
—John Dos Passos (1896–1970)
“The taking of a little prize,
Do not a single heart dispise.”
—Aurelian Townshend (c. 1583–c.1651)