May 20, 1956

Vagal and sympathetic effects on the pacemaker fibers in the sinus venosus of the heart

The Journal of General Physiology
O F HUTTER, W Trautwein

Abstract

1. Action potentials from sinus venosus and auricle fibers of spontaneously beating frog hearts have been recorded with intracellular electrodes. 2. Sinus fibers show a slow depolarization, the pacemaker potential, during diastole. The amplitude of this potential varies in different parts of the sinus. In some fibers the membrane potential falls by 11 to 15 mv. during diastole and the transition to the upstroke of the action potential is comparatively gradual. In other regions the depolarization develops more slowly and the action potential takes off more abruptly from a higher membrane potential. It is proposed that the fibers showing the largest fall in membrane potential during diastole are the pacemaker fibers of the heart, and that the rest of the preparation is excited by conduction. In auricle fibers the membrane potential is constant during diastole. 3. The maximum diastolic membrane potential and the overshoot of the action potential vary inversely with the amplitude of the pacemaker potential. The highest values were measured in auricle fibers. 4. Stimulation of vagi suppresses the pacemaker potentials. While the heart is arrested the membrane potential of the sinus fibers rises to a level above the maximum diastolic ...Continue Reading

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Mentioned in this Paper

External Ear
Sympathetic Nervous System
Vagal Stimulation
Protoplasm
Action Potentials
Shock
Sinus - General Anatomical Term
Vagus Nerve Structure
Auricle of External Ear
Metabolic Inhibition

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