The Influence of the Autonomic Nervous System on the Contraction of the Human Heart under Normal Circulatory Conditions.

The authors conclude that the autonomic influence on the contraction of the heart must play an essential role in the regulation of the circulation.

Abstract

Summary. A study has been made of the contraction of the left ventricle under the influence of various agents acting on the autonomic nervous system. The analyses were made with the help of electro‐kymography, electrocardiography and phonocardiography. Blocking of the vagus with methyl scopolamine nitrate was found to have the following effects: (1) an increase in the heart rate, (2) a decrease in the duration of systolic contraction, (3) an increase in the amplitude of the first and second heart sounds, (4) a rise in the arterial blood pressure and (5) a tendency to an increase in the degree of contraction of the left ventricle. The effect differs from that of adrenaline, administered intravenously, in that the heart rate and the blood pressure are affected considerably more than the contraction of the heart. The action of adrenaline, administered intravenously was intensified by blocking of the vagus. Blocking of the sympathetic nerves with dihydroergotamine was found to have the reverse effect to that of blocking of the vagus. The action of the former seemed to be intensified by the simultaneous intravenous injection of acetylcholine. Doses of dihydroergotamine of 1 to 1.5 mg were found to have only a slight inhibitory effect on the action of adrenaline, administered intravenously. The results are discussed with reference to the regulation of the circulation of the blood and of its distribution under normal circulatory cnoditions. The authors conclude that the autonomic influence on the contraction of the heart must play an essential role in the regulation of the circulation.