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Nature Reviews. Gastroenterology &... May 2022The primary function of the gut is to procure nutrients. Synchronized mechanical activities underlie nearly all its endeavours. Coordination of mechanical activities... (Review)
Review
The primary function of the gut is to procure nutrients. Synchronized mechanical activities underlie nearly all its endeavours. Coordination of mechanical activities depends on sensing of the mechanical forces, in a process called mechanosensation. The gut has a range of mechanosensory cells. They function either as specialized mechanoreceptors, which convert mechanical stimuli into coordinated physiological responses at the organ level, or as non-specialized mechanosensory cells that adjust their function based on the mechanical state of their environment. All major cell types in the gastrointestinal tract contain subpopulations that act as specialized mechanoreceptors: epithelia, smooth muscle, neurons, immune cells, and others. These cells are tuned to the physical properties of the surrounding tissue, so they can discriminate mechanical stimuli from the baseline mechanical state. The importance of gastrointestinal mechanosensation has long been recognized, but the latest discoveries of molecular identities of mechanosensors and technical advances that resolve the relevant circuitry have poised the field to make important intellectual leaps. This Review describes the mechanical factors relevant for normal function, as well as the molecules, cells and circuits involved in gastrointestinal mechanosensing. It concludes by outlining important unanswered questions in gastrointestinal mechanosensing.
Topics: Emotions; Gastrointestinal Tract; Humans; Mechanoreceptors; Muscle, Smooth; Neurons
PubMed: 35022607
DOI: 10.1038/s41575-021-00561-y -
Journal of Neurophysiology Sep 2018Cutaneous afferents convey exteroceptive information about the interaction of the body with the environment and proprioceptive information about body position and... (Review)
Review
Cutaneous afferents convey exteroceptive information about the interaction of the body with the environment and proprioceptive information about body position and orientation. Four classes of low-threshold mechanoreceptor afferents innervate the foot sole and transmit feedback that facilitates the conscious and reflexive control of standing balance. Experimental manipulation of cutaneous feedback has been shown to alter the control of gait and standing balance. This has led to a growing interest in the design of intervention strategies that enhance cutaneous feedback and improve postural control. The advent of single-unit microneurography has allowed the firing and receptive field characteristics of foot sole cutaneous afferents to be investigated. In this review, we consolidate the available cutaneous afferent microneurographic recordings from the foot sole and provide an analysis of the firing threshold, and receptive field distribution and density of these cutaneous afferents. This work enhances the understanding of the foot sole as a sensory structure and provides a foundation for the continued development of sensory augmentation insoles and other tactile enhancement interventions.
Topics: Action Potentials; Feedback, Physiological; Foot; Humans; Mechanoreceptors; Microelectrodes; Physical Stimulation; Postural Balance; Sensory Thresholds; Touch
PubMed: 29873612
DOI: 10.1152/jn.00848.2017 -
PLoS Computational Biology Dec 2022Sensory information is conveyed by populations of neurons, and coding strategies cannot always be deduced when considering individual neurons. Moreover, information...
Sensory information is conveyed by populations of neurons, and coding strategies cannot always be deduced when considering individual neurons. Moreover, information coding depends on the number of neurons available and on the composition of the population when multiple classes with different response properties are available. Here, we study population coding in human tactile afferents by employing a recently developed simulator of mechanoreceptor firing activity. First, we highlight the interplay of afferents within each class. We demonstrate that the optimal afferent density to convey maximal information depends on both the tactile feature under consideration and the afferent class. Second, we find that information is spread across different classes for all tactile features and that each class encodes both redundant and complementary information with respect to the other afferent classes. Specifically, combining information from multiple afferent classes improves information transmission and is often more efficient than increasing the density of afferents from the same class. Finally, we examine the importance of temporal and spatial contributions, respectively, to the joint spatiotemporal code. On average, destroying temporal information is more destructive than removing spatial information, but the importance of either depends on the stimulus feature analyzed. Overall, our results suggest that both optimal afferent innervation densities and the composition of the population depend in complex ways on the tactile features in question, potentially accounting for the variety in which tactile peripheral populations are assembled in different regions across the body.
Topics: Humans; Action Potentials; Touch; Mechanoreceptors; Neurons; Neurons, Afferent
PubMed: 36477028
DOI: 10.1371/journal.pcbi.1010763 -
American Journal of Physiology. Renal... Jan 2016All cells in the body experience external mechanical forces such as shear stress and stretch. These forces are sensed by specialized structures in the cell known as... (Review)
Review
All cells in the body experience external mechanical forces such as shear stress and stretch. These forces are sensed by specialized structures in the cell known as mechanosensors. Cells lining the proximal tubule (PT) of the kidney are continuously exposed to variations in flow rates of the glomerular ultrafiltrate, which manifest as changes in axial shear stress and radial stretch. Studies suggest that these cells respond acutely to variations in flow by modulating their ion transport and endocytic functions to maintain glomerulotubular balance. Conceptually, changes in the axial shear stress in the PT could be sensed by three known structures, namely, the microvilli, the glycocalyx, and primary cilia. The orthogonal component of the force produced by flow exhibits as radial stretch and can cause expansion of the tubule. Forces of stretch are transduced by integrins, by stretch-activated channels, and by cell-cell contacts. This review summarizes our current understanding of flow sensing in PT epithelia, discusses challenges in dissecting the role of individual flow sensors in the mechanosensitive responses, and identifies potential areas of opportunity for new study.
Topics: Animals; Epithelial Cells; Humans; Integrins; Intercellular Junctions; Ion Channel Gating; Ion Channels; Kidney Tubules, Proximal; Mechanoreceptors; Mechanotransduction, Cellular; Pressure; Stress, Mechanical
PubMed: 26662200
DOI: 10.1152/ajprenal.00373.2015 -
Gene Jul 2012A wide range of cell types depend on mechanically induced signals to enable appropriate physiological responses. The skeleton is particularly dependent on mechanical... (Review)
Review
A wide range of cell types depend on mechanically induced signals to enable appropriate physiological responses. The skeleton is particularly dependent on mechanical information to guide the resident cell population towards adaptation, maintenance and repair. Research at the organ, tissue, cell and molecular levels has improved our understanding of how the skeleton can recognize the functional environment, and how these challenges are translated into cellular information that can site-specifically alter phenotype. This review first considers those cells within the skeleton that are responsive to mechanical signals, including osteoblasts, osteoclasts, osteocytes and osteoprogenitors. This is discussed in light of a range of experimental approaches that can vary parameters such as strain, fluid shear stress, and pressure. The identity of mechanoreceptor candidates is approached, with consideration of integrins, pericellular tethers, focal adhesions, ion channels, cadherins, connexins, and the plasma membrane including caveolar and non-caveolar lipid rafts and their influence on integral signaling protein interactions. Several mechanically regulated intracellular signaling cascades are detailed including activation of kinases (Akt, MAPK, FAK), β-catenin, GTPases, and calcium signaling events. While the interaction of bone cells with their mechanical environment is complex, an understanding of mechanical regulation of bone signaling is crucial to understanding bone physiology, the etiology of diseases such as osteoporosis, and to the development of interventions to improve bone strength.
Topics: Bone and Bones; Humans; Intracellular Signaling Peptides and Proteins; Mechanoreceptors; Osteoblasts; Osteoclasts; Osteocytes; Signal Transduction; Stem Cells; Stress, Mechanical; Stress, Physiological
PubMed: 22575727
DOI: 10.1016/j.gene.2012.04.076 -
Journal of Neurobiology Nov 2002The Drosophila auditory system is presented as a powerful new genetic model system for understanding the molecular aspects of development and physiology of hearing... (Review)
Review
The Drosophila auditory system is presented as a powerful new genetic model system for understanding the molecular aspects of development and physiology of hearing organs. The fly's ear resides in the antenna, with Johnston's organ serving as the mechanoreceptor. New approaches using electrophysiology and laser vibrometry have provided useful tools to apply to the study of mutations that disrupt hearing. The fundamental developmental processes that generate the peripheral nervous system are fairly well understood, although specific variations of these processes for chordotonal organs (CHO) and especially for Johnston's organ require more scrutiny. In contrast, even the fundamental physiologic workings of mechanosensitive systems are still poorly understood, but rapid recent progress is beginning to shed light. The identification and analysis of mutations that affect auditory function are summarized here, and prospects for the role of the Drosophila auditory system in understanding both insect and vertebrate hearing are discussed.
Topics: Animals; Drosophila; Embryo, Nonmammalian; Genes, Insect; Hearing; Mechanoreceptors; Mutation
PubMed: 12382274
DOI: 10.1002/neu.10126 -
The Journal of the American Osteopathic... Aug 2019From its founding by Andrew Taylor Still, MD, DO, through the work of many contributors, one of the cornerstones of osteopathic medicine has been its ability to aid... (Review)
Review
From its founding by Andrew Taylor Still, MD, DO, through the work of many contributors, one of the cornerstones of osteopathic medicine has been its ability to aid health by promoting neuromuscular homeostasis. As part of the understanding of osteopathic medicine since the time of Still, the proper functioning of stretch receptor organs (SROs) of skeletal muscle have been recognized as having a central role in this homeostasis. In doing so, the complexities of these numerous and vital sensors are described, including recent findings regarding their structure, function, and the nature of their neural connections. In their homeostatic role, SROs conduct information centrally for integration in proprioceptive and autonomic reflexes. By virtue of their integral role in muscle reflexes, they are putatively involved in somatic dysfunction and segmental facilitation. In reviewing some well-established knowledge regarding the SRO and introducing more recent scientific findings, an attempt is made to offer insights on how this knowledge may be applied to better understand somatic dysfunction.
Topics: Humans; Manipulation, Osteopathic; Mechanoreceptors
PubMed: 31355890
DOI: 10.7556/jaoa.2019.094 -
Current Opinion in Neurobiology Aug 2005Mechanoreceptor cells of the somatosensory system initiate the perception of touch and pain. Molecules required for mechanosensation have been identified from... (Review)
Review
Mechanoreceptor cells of the somatosensory system initiate the perception of touch and pain. Molecules required for mechanosensation have been identified from invertebrate neurons, and recent functional studies indicate that ion channels of the transient receptor potential and degenerin/epithelial Na+ channel families are likely to be transduction channels. The expression of related channels in mammalian somatosensory neurons has fueled the notion that these channels mediate mechanotransduction in vertebrates; however, genetic disruption and heterologous expression have not yet revealed a direct role for any of these candidates in somatosensory mechanotransduction. Thus, new systems are needed to define the function of these ion channels in somatosensation and to pinpoint molecules or signaling pathways that underlie mechanotransduction in vertebrates.
Topics: Animals; Humans; Mechanoreceptors; Neurons; Sensation; Signal Transduction
PubMed: 16023849
DOI: 10.1016/j.conb.2005.06.005 -
Annual Review of Neuroscience Jul 2013Sensory hair cells are exquisitely sensitive vertebrate mechanoreceptors that mediate the senses of hearing and balance. Understanding the factors that regulate the... (Review)
Review
Sensory hair cells are exquisitely sensitive vertebrate mechanoreceptors that mediate the senses of hearing and balance. Understanding the factors that regulate the development of these cells is important, not only to increase our understanding of ear development and its functional physiology but also to shed light on how these cells may be replaced therapeutically. In this review, we describe the signals and molecular mechanisms that initiate hair cell development in vertebrates, with particular emphasis on the transcription factor Atoh1, which is both necessary and sufficient for hair cell development. We then discuss recent findings on how microRNAs may modulate the formation and maturation of hair cells. Last, we review recent work on how hair cells are regenerated in many vertebrate groups and the factors that conspire to prevent this regeneration in mammals.
Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Hair Cells, Auditory; Humans; Mechanoreceptors; Regeneration
PubMed: 23724999
DOI: 10.1146/annurev-neuro-062012-170309 -
Channels (Austin, Tex.) 2012Cutaneous mechanoreceptors are localized in the various layers of the skin where they detect a wide range of mechanical stimuli, including light brush, stretch,... (Review)
Review
Cutaneous mechanoreceptors are localized in the various layers of the skin where they detect a wide range of mechanical stimuli, including light brush, stretch, vibration and noxious pressure. This variety of stimuli is matched by a diverse array of specialized mechanoreceptors that respond to cutaneous deformation in a specific way and relay these stimuli to higher brain structures. Studies across mechanoreceptors and genetically tractable sensory nerve endings are beginning to uncover touch sensation mechanisms. Work in this field has provided researchers with a more thorough understanding of the circuit organization underlying the perception of touch. Novel ion channels have emerged as candidates for transduction molecules and properties of mechanically gated currents improved our understanding of the mechanisms of adaptation to tactile stimuli. This review highlights the progress made in characterizing functional properties of mechanoreceptors in hairy and glabrous skin and ion channels that detect mechanical inputs and shape mechanoreceptor adaptation.
Topics: Animals; Humans; Ion Channels; Mechanoreceptors; Neurons; Skin; Spinal Cord; Touch
PubMed: 23146937
DOI: 10.4161/chan.22213