Abstract
The spinal cord is an important integrative center for blood pressure control. Spinal sensory fibers send projections to sympathetic preganglionic neurons of the thoracic spinal cord and drive sympathetically-mediated increases in blood pressure. While these reflexes responses occur in able-bodied individuals, they are exaggerated following interruption of descending control – such as occurs following spinal cord injury. Similar reflex control of blood pressure may exist in disease states, other than spinal cord injury, where there is altered input to sympathetic preganglionic neurons. This review primarily focuses on mechanisms wherein visceral afferent information traveling via spinal nerves influences sympathetic nerve activity and blood pressure. There is an abundance of evidence for the widespread presence of this spinal reflex arch originating from virtually every visceral organ and thus having a substantial role in blood pressure control. Additionally, this review highlights specific endogenous eicosanoid species, which modulate the activity of afferent fibers involved in this reflex, through their interactions with transient receptor potential (TRP) cation channels.
Highlights
Physiological mechanisms of blood pressure control involve complex interactions between neural and humoral factors, which work hand-in-hand to ensure optimal delivery of nutrient rich blood to all the cells of the body
Spinal sympathetic reflex arcs are important drivers of normal physiological responses and the spinal cord itself is an integrative center for maintenance of arterial blood pressure
Spinal afferent fibers arising from the viscera robustly activate sympathetic preganglionic neurons via intraspinal circuitry
Summary
Physiological mechanisms of blood pressure control involve complex interactions between neural and humoral factors, which work hand-in-hand to ensure optimal delivery of nutrient rich blood to all the cells of the body. Important are the effects of the sympathetic nervous system. Sympathetic postganglionic neurons innervate blood vessels to regulate vascular smooth muscle tone and peripheral resistance. The rostral ventrolateral medulla is arguably one of the most critical cites for establishing baseline blood pressure as it sends tonic impulses to sympathetic preganglionic neurons located within the intermediolateral cell column of the thoracic spinal cord. The spinal cord is often described as a mere relay station between the brainstem and the periphery, clinical and experimental evidence highlights the important role of intraspinal reflex circuits in blood pressure regulation
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