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Electrophysiology
Published in A. Bakiya, K. Kamalanand, R. L. J. De Britto, Mechano-Electric Correlations in the Human Physiological System, 2021
A. Bakiya, K. Kamalanand, R. L. J. De Britto
Biopotentials are generated as a result of the electrochemical activity of the cells that are the components of the nervous, muscular and granular tissue. The electrical activity of the cell is generated via in and out ion movement (K+, Na+ and Cl−) through the cell membrane (Van Drongelen, 2010). Generally, the potentials are in two states (active and resting potential). The active potential is generated when cells are stimulated. The membrane potential when the cell is inactive is the resting potential. At resting state, the potassium ion is more permeable in the cell membrane when compared to the sodium and potassium ion concentrations is higher in the interior of the cell when compared to the exterior of the cell. The diffusion gradient of potassium ion arises toward the exterior of the cell that creates more negative ions in the interior of the cell. At steady or depolarization state, the diffusion gradient of potassium ion is in equilibrium and balanced by the electric field with the polarization voltages of −70 mV (Thakor, 2015; Webster, 1984). If the cells are electrically stimulated, the diffusion gradient of potassium ion increases and diffuse toward the interior of the cells that creates more potential. If the active potentials reach +40 mV, the permeability of the potassium ion decreases and the sodium ion increases causing resting potential. This cycle produces the several cellular potentials called as action potentials (Yazıcıoğlu et al., 2009; Thakor, 2015).
Force Generation Mechanism of Skeletal Muscle Contraction
Published in Yuehong Yin, Biomechanical Principles on Force Generation and Control of Skeletal Muscle and their Applications in Robotic Exoskeleton, 2020
It is recognized that motoneuron is the end of control signal for skeletal muscle contraction. The control signal, encoded by the AP, is sent to the neuromuscular junction through the axon of neuron. AP is the basic unit of nerve signal. The earliest systematic and quantitative research on AP was conducted by Hodgkin and Huxley [4] using squid’s giant axon. There are numerous ion channels on the membrane of neuron, including Na+ channel, K+ channel, Cl− channel, and Ca2+ channel. The ion concentration is unequal inside and outside the membrane and is generally kept constant by the cell. For instance, the K+ concentration inside the membrane ([K+]i) is higher than that outside the membrane ([K+]o). Oppositely, [Na+]o and [Ca2+]o are higher than [Na+]i and [Ca2+]i, respectively, and [Cl−]o and [Cl−]i can be treated as equal. The ion concentration (charge concentration) difference across the membrane contributes to the formation of membrane potential. AP is actually a special kind of membrane potential.
Signals, Noise, and Thresholds
Published in Ben Greenebaum, Frank Barnes, Bioengineering and Biophysical Aspects of Electromagnetic Fields, 2018
The electrochemical potential across the cell membrane is an energy source for many processes.44 The Na,Ca-exchanger, for instance, is a membrane protein that picks up a sodium ion on the outside and then goes through a cycle in the course of which it drops the sodium ion off on the inside. The protein couples the energetically downhill movement of sodium to uphill transport of calcium. In the course of the cycle, a calcium ion is picked up on the inside and pumped, against the electrochemical potential, to the outside. The membrane potential is maintained by ATP-driven ion pumps. The most common of these is Na,K-ATPase. This is a membrane protein that, in the course of its catalytic cycle, hydrolyzes one ATP and uses the released energy to transport three sodium ions out of the cell and bring two potassium ions in.
Emerging electrolyte-gated transistors for neuromorphic perception
Published in Science and Technology of Advanced Materials, 2023
Cui Sun, Xuerong Liu, Qian Jiang, Xiaoyu Ye, Xiaojian Zhu, Run-Wei Li
Typically, a neuron is composed of three compartments, namely, the dendrites, the axons, and the soma (cell body). The dendrites with a tree structure receive signals from other neurons and the axon passes the newly-generated neural spike signals as the output to other neurons. The soma functions as the key computing units for signal integration and generation (Figure 4(a)). The neurons can become inactive (at the resting state) or active (at the firing state), depending on the external stimulation conditions that control the neuronal membrane potential. For neurons at the resting state with a potential of ~-70 mV, the input neural spikes activate ion channels on the neuronal membrane that tune the flow of charged ions (such as Na+, K+, Cl−, etc.) across the cell membrane (Figure 4(b)) thus pulling up the membrane potential. When a threshold membrane potential (e.g. −55 mV) is reached, the neuron is set to the firing state and creates an action potential as the output signal [105,107,108].
Electrochemical evaluation of ion substituted-hydroxyapatite on HeLa cells plasma membrane potential
Published in Cogent Engineering, 2019
Bernard Owusu Asimeng, Elvis Kwason Tiburu, Elsie Effah Kaufmann, Lily Paemka, Claude Fiifi Hayford, Samuel Essien-Baidoo, Obed Korshie Dzikunu, Prince Atsu Anani
It is reported that disrupting the plasma membrane potential of cancer cells may trigger apoptosis (Zhang, Chen, Gueydan, & Han, 2017). Generally, cell plasma membranes generate potential (membrane potential) because of the imbalance of charges between the intracellular and extracellular environment. This arises from the presence of different ion channels which allow distinct ions such as Na+, K+, Ca2+ and Cl− access through the voltage-gates of the ion channels based on their specific size. Because of the difference in the number of ions within the cytoplasm and the extracellular medium, a voltage difference (electrochemical gradient) is always evolving. A normal cell tries to balance the ion concentration across the plasma membrane to achieve a resting potential through polarization. At resting potential, the cytoplasm becomes more negative. That is, more Na+ are sent outside and K+ are kept inside the cytoplasm (polarization). Typically, normal cells generate stimuli through polarization, for example, during muscle contraction (Lodish, Berk Arnold, Lawrence, & Baltimore David, 2000). On the contrary, cancer cells generate stimuli through plasma membrane depolarization (more Na+ are taken up by the cell and the cytoplasm becomes less negative). Depolarization generates strong stimuli that communicate faster, causing rapid proliferation (Yang & Brackenbury, 2013).
Multiscale modelling via split-step methods in neural firing
Published in Mathematical and Computer Modelling of Dynamical Systems, 2018
Pavol Bauer, Stefan Engblom, Sanja Mikulovic, Aleksandar Senek
The chemical connections between neurons are handled via synapses, where neurotransmitters are extruded into the extracellular space by the presynaptic neuron. The neurotransmitters form a part of a chemical process which may initiate a potential wave into the postsynaptic neuron – this wave is known as the action potential. During the action potential, the membrane potential quickly rises and falls, and the resulting signal propagates along the cell [1]. The process that underlies this propagation is the regulation of ion concentrations in both the intracellular cytoplasm and the extracellular space caused by integral membrane proteins called ion channels.