Electromechanical Coupling Mechanisms Of Tactile Cells

Touch,as one of the five important human senses,which allows us to perceive a wealth of information from the physical world.Tactile cells are the executors of the tactile system that convert external mechanical stimuli into neural electrical signals.They can convert fovariousrms of mechanical stimuli into different types of electrical signals,which are the basis for the generation of touch.Dysfunction of touch cells can lead to pathological symptoms such as hyperalgesia or loss of touch.Therefore,studying the mechanical-electrial coupling mechanisms of tactile cells is of great significance to our understanding of touch,treatment of tactile diseases,and even the study of artificial bionic touch.Tactile cells have two main physiological functions:(1)stimulate downstream nerve cells by releasing neurotransmitters through vesicular transport;(2)generate action potentials under mechanical stimuli.The membrane tension of tactile cell changes under mechanical stimuli,which in turn affects vesicle transport and prompts cells to release neurotransmitters.However,how mechanical stimuli regulate the dynamics of vesicle transport remains unclear.Regarding the generation of action potentials under mechanical stimuli,previous studies have mainly focused on the scale of afferent fibers,and have made a detailed classification for different electrical signals generated in afferent fibers.However,an afferent fiber usually receives electrical signals from a large number of touch cells at the same time,so the electrical signals difference of afferent fiber may result from the difference in the response of touch cells to mechanical stimuli.However,the mechanical-electrial conversion mechanism at the cellular scale is still lacking,and how touch cells respond to different mechanical stimuli at the cellular scale is still unclear.Aiming at the above two questions,this paper studies the regulation mechanism of mechanical stimuli on vesicle transport in touch cells and the mechanical-electrical coupling response characteristics of touch cells under different forms of mechanical stimuli.Firstly,this paper establishes a multi-scale dynamic model for vesicle transport,which comprehensively considers factors such as cell volume regulation,cell membrane tension,exocytosis,and endocytosis,to study the dynamics of vesicle transport in touch cells under osmotic shock and mechanical compression.The results show that hypoosmotic shock promotes exocytosis,whereas hyperosmotic shock promotes endocytosis.Endocytosis and exocytosis,in turn,significantly reduce the magnitude of changes in cell membrane tension,thereby avoiding cell rupture caused by the drastic change in membrane tension.However,under mechanical compression,vesicle transport shows different response patterns at different loading speeds due to the competition between cell volume regulation and loading speed.During fast compression,the area and tension of the cell membrane increase,which promotes exocytosis.In turn,the increase in the vesicle transport rate reduces the changes in membrane tension and volume.During slow compression,the cell shrinks,causing a decrease in cell membrane tension and promoting endocytosis.In this case,the increase in vesicle transport rate instead promotes the changes in membrane tension and volume.Next,this paper comprehensively considers mechanosensitive(MS)channels,voltage-gated channels,ion pumps,membrane potential,sodium,potassium,chloride ion transport and other factors to establish a mechanical-electrial coupling model of tactile cells,and study the effect of different MS channels on the mechanical-electrial response properties of tactile cells.The results show that the rapidly adapting(RA)MS channels are more sensitive to loading speed,while the slowly adapting(SA)MS channels are more sensitive to loading depth.Therefore,the former facilitates tactile cells to perceive dynamic mechanical stimuli,while the latter facilitates tactile cells to perceive static mechanical stimuli.Finally,this paper further investigates the roles of RA and SA MS channels in texture perception,as well as the effects of finger sliding speed and contact force on texture perception.The results show that touch cells containing RA MS channels are able to perceive textures in a range of wavelengths in dynamic sliding mode.And the increase of sliding speed and contact force can broaden the sensing range of tactile cells,but a larger sliding speed will reduce the ability of tactile cells to perceive fine textures.In contrast,touch cells containing SA MS channels are unable to perceive texture in dynamic sliding mode,but could generate multiple action potentials in static contact mode.Since rough textures are mainly sensed through the distance between tactile cells,SA MS channels play an important role in rough texture perception.In summary,this paper explores the vesicle transport properties of touch cells under mechanical stimuli and their mechanical-electrial response properties under different forms of mechanical stimuli.We find that hypertonic and hypotonic stimuli can trigger different vesicle transport modes,and the vesicle transport modes of touch cells under mechanical compression are significantly dependent on the loading rate.This paper also clarifies that RA MS channels can respond to dynamic mechanical loads,while SA MS channels can respond to static mechanical loads,and reveals the regulatory rules of MS channels’ mechanical properties,finger sliding speed and contact force on texture perception.These results will play an important role in understanding of the tactile perception process,provide theoretical guidance for other aspects of tactile perception research,and offer an important scientific basis for bionic tactile design.