Recording of sympathetic activity from muscle nerves revealed vasoconstrictor impulses modulated by baroreflex influence, with a reflex delay of 0.9-1.4 seconds from arterial pulse to inhibition.
Observational
This physiological study characterizes human sympathetic muscle nerve activity, demonstrating its role as vasoconstrictor impulses modulated by baroreflexes and external stimuli.
Abstract Multiunit sympathetic activity was recorded from muscle nerve fascicles in the median or peroneal nerve of resting, relaxed human subjects. The impulses, which were reversibly abolished by a Sympathetic ganglion blocking agent, were grouped in the pulse rhythm, and series of such pulse rhythmic bursts of impulses regularly appeared during spontaneously occurring blood pressure reductions, whereas temporary blood pressure elevations were associated with neural silence. The findings agree with the notion that the sympathetic muscle nerve activity recorded consists of vasoconstrictor impulses, the outflow of which is modulated by a strong phasic and tonic inhibitory baroreflex influence. The reflex delay from an arterial pulse wave to the corresponding inhibition of efferent sympathetic activity was 0.9–1.4 seconds, depending on the recording site. Several stimuli, such as sudden chest compression, a rapid deep breath or an electrical shock against the skin, caused a transient inhibition of the sympathetic discharges lasting a few seconds.
Delius et al. (1972) conducted an observational in Resting, relaxed human subjects. Physiological stimuli and sympathetic ganglion blocking agent was evaluated on Characteristics of sympathetic muscle nerve activity. Recording of sympathetic activity from muscle nerves revealed vasoconstrictor impulses modulated by baroreflex influence, with a reflex delay of 0.9-1.4 seconds from arterial pulse to inhibition.