Fifty years of microneurography: learning the language of the peripheral sympathetic nervous system in humans

Abstract

As a primary component of homeostasis, the sympathetic nervous system enables rapid adjustments to stress through its ability to communicate messages among organs and cause targeted and graded end organ responses. Key in this communication model is the pattern of neural signals emanating from the central to peripheral components of the sympathetic nervous system. But what is the communication strategy employed in peripheral sympathetic nerve activity (SNA)? Can we develop and interpret the system of coding in SNA that improves our understanding of the neural control of the circulation? In 1968, Hagbarth and Vallbo (Hagbarth KE, Vallbo AB. Acta Physiol Scand 74: 96-108, 1968) reported the first use of microneurographic methods to record sympathetic discharges in peripheral nerves of conscious humans, allowing quantification of SNA at rest and sympathetic responsiveness to physiological stressors in health and disease. This technique also has enabled a growing investigation into the coding patterns within, and cardiovascular outcomes associated with, postganglionic SNA. This review outlines how results obtained by microneurographic means have improved our understanding of SNA outflow patterns at the action potential level, focusing on SNA directed toward skeletal muscle in conscious humans.

Heterogeneous baroreflex control of sympathetic action potential subpopulations in humans

“…Indeed, many forms of physiological stress strongly recruit previously silent larger and faster conducting APs including those activating the arterial chemoreflex and muscle metaboreflex along with manoeuvres involving volitional effort or perceptual stress (e.g. Valsalva's Manoeuvre, voluntary apnoea) (Steinback et al 2010;Salmanpour et al 2011b;Badrov et al 2016b;Klassen et al 2017;Shoemaker, 2017;Shoemaker et al 2018). In these other manoeuvres, it remains possible that baroreflex resetting is responsible for the recruitment of previously silent APs; however, the current data argue against that mechanism.…”

“…Unlike other forms of stress (e.g. chemical, metabolic, or apnoeic) (Malpas et al 1996;Klassen et al 2017;Shoemaker et al 2018), baroreflex unloading represents a weak reflex for recruiting larger, latent AP clusters (i.e. high-threshold axons) until severe levels, such as -80 mmHg LBNP, with some inter-individual variability (Salmanpour et al 2011a;Badrov et al 2015).…”

The role of the paravertebral ganglia in human sympathetic neural discharge patterns

“…Furthermore, multi‐unit and single‐unit recordings of axonal firing patterns within MSNA bursts have revealed additional layers of complexity regarding communication strategies contained within the sympathetic neural signal in humans (Shoemaker et al . 2014, ; Macefield & Wallin, ). For instance, under baseline conditions, recruited axons fire with relatively low probability (e.g.…”

Brain-Computer Interface Data Classification Based on Support Vector Machine

“…Brain is the human nervous system control center, which controls people's thinking, behavior, emotions and other activities (Manfredsson et al, 2018;Shoemaker et al, 2018;Schoedel et al, 2018;Chen et al, 2018;Mirfeizi et al, 2017;Uribe-Perez and Pous, 2017;Chen et al, 2018;Schoedel et al, 2018;Shoemaker et al, 2018). After the brain parses and processes information of external environment, it uses external nerve conduction pathways and muscle tissues to control the peripheral equipment or interact with the external environment.…”