Applied physiology of nociception
Pamela E Macintyre, Suellen M Walker, David J Rowbotham in Clinical Pain Management, 2008
Neurons in peripheral nerves can be classified according to morphological, electrophysiological, and biochemical characteristics (Table 1a.1 and Figure 1a.1).3,4,5,6 There are two types of primary afferent fiber involved in nociception: Aδ- and C-fibers (Table 1a.2). The two principal functions of primary afferent neurons are stimulus transduction and transmission of encoded stimulus information to the CNS. The cell body of such a neuron is located in the dorsal root ganglion of a spinal nerve (or trigeminal ganglion for the trigeminal nerve), and the smaller diameter cell bodies are associated with nociception. Each axon possesses two branches, one projecting to the periphery (peripheral process), where its terminal is sensitive to noxious stimuli, and one projecting to the CNS (central process), where it synapses with CNS neurons. Eighty percent of nociceptor primary afferents are nonmyelinated C-fibers.
Neuronal Regulation of the Immune System in Cardiovascular Diseases
Shyam S. Bansal in Immune Cells, Inflammation, and Cardiovascular Diseases, 2022
The circumventricular organs (CVOs), located around the third and fourth ventricles, are particular brain regions characterized by a leaky blood–brain barrier (BBB) and dense vascularization (Ballabh, Braun, & Nedergaard, 2004). These specialized areas are points of communication between the blood, the brain parenchyma, and the cerebrospinal fluid. The peripheral nervous system (PNS) connects the CNS to peripheral tissues and is mainly organized in two branches comprising the somatic and autonomic systems. Each of these systems further consists of two arms of sensory or afferent neurons – transporting the information from the periphery to the CNS – and motor or efferent neurons, delivering responses toward the effector tissues (Reardon et al., 2018). Additionally, the humoral route regulated by the hypothalamus-pituitary-adrenal axis provides further control of neuroimmune communication in health and disease.
Motor Function and ControlDescending Tracts
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
A reflex can be defined as an automatic or involuntary stereotype response to a stimulus mediated by a receptor, an afferent and efferent pathway and an effector organ. The reflex pathway generally consists of a receptor and an afferent neuron and is integrated by interneurons in the spinal cord. The final common efferent path is a motor neuron to the effector organ. Spinal cord ventral horn motor neurons may be either α motor neurons (14 μm in diameter and rapid conduction velocity) or γ motor neurons (5 μm in diameter and slower conduction velocity). There are also interneurons, which are highly excitable and may have high spontaneous firing rates. The Renshaw cell is a special interneuron that receives collateral branches of motor neuron axons. The Renshaw cell provides inhibitory connections with the same or neighbouring motor neurons via its own axons.
Communication between the gut microbiota and peripheral nervous system in health and chronic disease
Published in Gut Microbes, 2022
Tyler M. Cook, Virginie Mansuy-Aubert
Neuronal transmission allows for nearly instantaneous processing of sensory input or generation of motor output. This rapid signaling of peripheral neurons in the gut is critical for homeostatic mechanisms such as GI motility, secretion, and even immune response modulation.39 The peripheral nervous system (PNS) consists of vagal and spinal sensory (afferent) neurons, autonomic motor (efferent) neurons, and enteric neurons (Figure 2). Afferent neurons send information from the periphery to the brain or spinal cord, while efferent neurons project out from the central nervous system (CNS) to peripheral organs. Classifying by anatomical distribution, the twelve cranial nerves project from the brain/brainstem and spinal nerves from the spinal cord. The autonomic system is divided into sympathetic, parasympathetic, and enteric nervous systems (ENS).
The triple function of the capsaicin-sensitive sensory neurons: In memoriam János Szolcsányi
Published in Temperature, 2023
Erika Pintér, Zsuzsanna Helyes, Éva Szőke, Kata Bölcskei, Angéla Kecskés, Gábor Pethő
Prof. János Szolcsányi spent 60 years studying the properties of capsaicin-sensitive sensory neurons. The existence of the latter subpopulation of primary afferent neurons itself has been adopted by the scientific community as a result of his extensive and fruitful research activity. His research group has provided substantial evidence for the triple function of the peptidergic subgroup of the capsaicin-sensitive sensory neurons including classical afferent function, local efferent tissue responses and remote, hormone-like anti-inflammatory and antinociceptive actions. This latter phenomenon was named “sensocrine” function by his own words. These discoveries have, and in the future certainly will have, broad implications for studying pathophysiological regulation of inflammation and pain as well as for the development of novel analgesic drugs acting directly on peripheral nociceptors. The immunohistological pictures shown below demonstrate co-localization of TRPV1 and TRPA1 channels, CGRP and SOM in primary sensory neurons from the L4 dorsal root ganglion of the rat using the RNAscope method (Figure 5). These four proteins/peptides are not only characteristic markers of these neurons but also cornerstones of the splendid research work performed by János Szolcsányi and his coworkers.
Solid lipid nanoparticles and nanostructured lipid carrier-based nanotherapeutics for the treatment of psoriasis
Published in Expert Opinion on Drug Delivery, 2021
Capsaicin is the main constituent of the plant Capsicum annum belonging to the family Solanaceae. It functions majorly at the primary afferent neurons of C-fibers in the nerves of somatic sensory system [41]. The anti-inflammatory property of capsaicin is attributed to the production of nitric oxide in peripheral macrophages, prostaglandin E2 (PGE2) inhibition and release of substance P [42]. In a study, capsaicin has also been found to translate hypoxia-inducible factor-1α (HIF-1α) gene in hyperproliferated psoriatic skin [43]. A double-blind study was carried out on patients with moderate and severe psoriasis. After 6 weeks of topical capsaicin treatment, a significant reduction in erythema, redness, itching, and scaling was observed which disappeared upon continued use. These outcomes suggested the application of capsaicin in curing psoriasis [44].
Related Knowledge Centers
- Axon
- Central Nervous System
- Dendrite
- Peripheral Nervous System
- Sensory Neuron
- Ganglion
- Sensory Nervous System
- Sense
- Neuron
- Soma