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Nonadrenergic Innervation of Blood Vessels To Skeletal Muscles
Published in Geoffrey Burnstock, Susan G. Griffith, Nonadrenergic Innervation of Blood Vessels, 2019
The preganglionic nerve fibers for the blood vessels of the lower extremities arise from the T12 to L5 spinal cord segments.29-32 Nerve fibers originating from the T12 to L3 segments are vasoconstrictors; those arising from segments L2 to L5 are vasodilators. The greatest vasoconstrictor outflow originates from the segments L1 to L3; the segment L4 is the origin of the greatest vasodilator outflow in the cat.31 Preganglionic fibers from the above-mentioned T12 to L5 segments descend through the chain ganglia to synapse with postganglionic neurons located chiefly in the L1 to S3 chain ganglia.30,33-34 Postganglionic nerve fibers reach the spinal nerves that supply the hindlimb muscles in a way similar to that previously described for the upper extremities (Figure 5).
Neural Control of the Intestinal Circulation and its Interaction With Autoregulation
Published in Irving H. Zucker, Joseph P. Gilmore, Reflex Control of the Circulation, 2020
Gerald A. Meininger, Harris J. Granger
Origin and Distribution of Sympathetic Innervation. Autonomic nervous control of the intestine can be subdivided into three components consisting of the sympathetic, parasympathetic, and enteric nervous systems. Of these the splanchnic circulation receives its primary innervation from the sympathetic nervous system (Fig. 1). The sympathetic nerves supplying the digestive organs arise from the thoracic (T1–T12) and lumbar (L1–L3) portions of the spinal cord as preganglionic nerve fibers. After leaving the spinal cord, these fibers travel through the paravertebral sympathetic chain ganglia on their way to synapse in one of three major prevertebral ganglia that lie near the roots of their namesake arteries: the celiac ganglion, the superior mesenteric ganglion, or the inferior mesenteric ganglion. From these ganglia arise the postganglionic nerve fibers that travel along with the celiac, superior mesenteric, and inferior mesenteric arteries and distribute to the individual digestive organs. An exception is the sympathetic postganglionic fibers that distribute to the salivary glands that arise from the superior cervical ganglion. Postganglionic fibers originating from the celiac ganglion supply the esophagus, stomach, liver, pancreas, and proximal duodenum. Fibers originating from the superior mesenteric ganglion supply the distal duodenum, jejunum, lieum, and proximal colon. The distal colon and rectum receive postganglionic fibers that arise from the inferior mesenteric ganglion. The major splanchnic nerves carrying the preganglionic sympathetic supply to these ganglia include the greater splanchnic nerve, the lesser splanchnic nerve, the smallest or renal splanchnic nerve, and two upper lumbar nerves (Granger et al., 1985; Goodman and Gilman, 1980; Carpenter, 1976; Brooksby and Donald, 1970). Neural transmission in the prevertebral ganglia, between pre- and postganglionic fibers, involves the neurotransmitter acetylcholine, whereas postganglionic neurotransmission is via norepinephrine. The noradrenergic neurons that innervate intestinal blood vessels also contain neuropeptide Y and ATP (Cooke, 1986). Yet, due to a lack of specific antagonists the transmitter roles of these substances are not precisely understood. Blood vessels within the digestive organs receive their innervation directly from the postganglionic sympathetic fibers. The vascular effects of sympathetic nerves will be discussed below.
Anatomical considerations
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Manual of Neuroanesthesia, 2017
Sympathetic nerve fibers (efferent) emerge from the first thoracic (T1) to second lumbar (L2) segment of the spinal cord (thoracolumbar outflow). This part of the spinal cord (T1-L2) possesses a lateral horn in addition to anterior and posterior horns present in the other part of the spinal cord. The cell body of the sympathetic connector neuron is located in the lateral horn of the spinal cord (Figure 1.12).3 The myelinated axons of these cells pass through the anterior nerve root of the spinal nerve. From the spinal nerve, these fibers pass via the white rami communicantes to reach the paravertebral ganglion of the sympathetic trunk on either side of the vertebral column. These are the preganglionic fibers. Sympathetic trunks (or sympathetic chains) are elongated chains of sympathetic nerve fibers running along each side of the vertebral column (paravertebral) with a number of sympathetic ganglia along its length. The number of ganglia is variable.8 Generally, there are 3 ganglia in the cervical region (superior, middle, and inferior cervical ganglia), 11–12 ganglia in the thoracic region, 4–5 ganglia in the lumbar region, and 4–5 ganglia in the sacral region. The two trunks end by joining caudally to form a single ganglion called the ganglion impar.8 The inferior cervical and first thoracic ganglion are often fused to form the stellate ganglion.2 Once the preganglionic fibers reach the ganglion of the sympathetic trunk, these fibers may take one of the following courses (Figure 1.12).2,8 (1) These fibers may synapse with another cell (postganglionic neuron) in the ganglion. The postganglionic nerve fibers (nonmyelinated) reach the spinal nerve via gray rami communicantes and are distributed via the branches of spinal nerves. (2) Some preganglionic fibers may travel up or down via the sympathetic trunk to reach another ganglion higher or lower in the sympathetic chain before synapsing with the postganglionic neurons. The postganglionic nerve fibers than pass through the gray rami communicantes to reach the spinal nerve and are distributed along with the nerve and its branches. (3) A few preganglionic fibers may leave the ganglion of sympathetic trunk without synapsing via the visceral branches of sympathetic trunk, such as cardiac, pulmonary, and splanchnic nerves, to reach the autonomic nerve plexuses (cardiac, pulmonary, celiac, mesenteric, and renal nerve plexuses). The preganglionic fibers synapse with the postganglionic fibers in these plexuses and the postganglionic fibers supply the blood vessels, smooth muscles, and glands of the visceral organs.2,3
The future of cardioneuroablation in cardiovascular medicine
Published in Expert Review of Cardiovascular Therapy, 2022
Tolga Aksu, Asad Khan, Henry Huang
Different GP sites demonstrated different acute neuromodulation responses during radiofrequency application [65]. Vagal response was most commonly observed at the LSGP site, and less often at the LIGP and RIGP sites, 34.2% and 7.9% of cases, respectively while ablation of RSGP increased heart rate acutely without any vagal response. In the human heart, postganglionic vagal nerve fibers travel from RSGP to the sinoatrial node, and it is likely that ablation around sinoatrial junction first affects postganglionic nerve fibers before affecting epicardial ganglia which likely causes an increase in heart rate by blocking parasympathetic innervation of the sinoatrial node without vagal discharge effect [66].