Effect of Variation of Blood Pressure on the Autonomic Nervous System

Summary

1. Increase in blood pressure induced by adrenalin or infusion of Ringer's solution leads to a decrease in pupillary diameter and to a relaxation of the nictitating membrane. A fall in the blood pressure induced by amylnitrite leads to a dilation of the normal and of the sympathectomized pupil. These observations indicate that a rise in blood pressure produces parasympathetic excitation and sympathetic inhibition, whereas a fall in blood pressure has the opposite results. 2. The effects produced by variations of blood pressure are still present after bilateral vagotomy and denervation of the carotid sinuses. 3. The effects of variations of blood pressure are not restricted to the visceral nervous system but extend to the somatic nervous system, inasmuch as increase in blood pressure is associated with decreased somatic excitability and decrease in pressure is associated with increased somatic excitability.