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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).
Targeting the Nervous System
Published in Nathan Keighley, Miraculous Medicines and the Chemistry of Drug Design, 2020
A resting potential of around −65 mV is maintained by the active transport of Na+ ions out of the nerve axon and K+ ions into the axon via intrinsic protein channels that make up the ‘sodium-potassium pump’. Three sodium ions are pumped out for every two potassium ions that enter the axon. Meanwhile, K+ ions are able to diffuse back out of the axon through specific ion channels, while sodium ion channels are mostly closed. This creates an electrochemical gradient; tissue fluid outside the neurone is positive compared to the axon membrane, which is said to be polarised.
Neuronal Function
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
When the flux of ions ceases, the membrane will repolarize to its resting potential. The rate at which it repolarizes depends on membrane resistance per unit area (Rm) and capacitance per unit area (Cm). The time required for the membrane potential to decay to 37% of its peak value is called the membrane time constant (TM), which is the product of membrane resistance and capacitance, that is, TM = Rm × Cm.
Ketogenic diet: overview, types, and possible anti-seizure mechanisms
Published in Nutritional Neuroscience, 2021
Mohammad Barzegar, Mohammadreza Afghan, Vahid Tarmahi, Meysam Behtari, Soroor Rahimi Khamaneh, Sina Raeisi
Two-pore domain potassium (K2P) channels, also known as potassium leak channels, are a major and distinct subclass of the potassium channel superfamily. They have been discovered in a wide variety of mammalian cells including neurons, myocytes, glia, and many different types of epithelial cells. These channels are structurally different from most other classes of potassium channels which form a functional tetramer. It has been shown that each subunit of K2P channels has two pore-forming regions and four trans-membrane segments, and thus, they form functional dimers. Functionally, these channels are spontaneously active leading to continuous efflux of potassium ions through the cell membrane which is necessary for setting a hyperpolarized resting potential of the cell membrane. Therefore, K2P channels may directly influence the duration and frequency of action potential firings [56,58–60]. These channels can be also modulated by a variety of physical, chemical and natural factors including voltage, temperature, mechanical pressure, protons (pH), and volatile anesthetics. It has been suggested that K2P channels may also be activated by ketone bodies and certain fatty acids as well [59,61]. Thus, KD-induced raises in blood ketone bodies and fatty acids as well may regulate neuron membrane excitability by activating K2P channels, and this can be assumed as another probable anticonvulsant mechanism of KD.
The ‘collateral side’ of mood stabilizers: safety and evidence-based strategies for managing side effects
Published in Expert Opinion on Drug Safety, 2020
Laura Orsolini, Simone Pompili, Umberto Volpe
The mechanism of action of Li is still not completely understood and several neurotransmitters and pathways have been hypothesized. Li competes for access to transport mechanism and binding site with other biological important cations (sodium, potassium, calcium, magnesium), including Sodium Potassium Pump (e.g. Na+/K+-ATPase) that is responsible for resting potential in neurons and other cells and mitochondrial Sodium Calcium Pump (e.g. Na+/Ca++ exchanger, NCLX), providing protection against damage to brain mitochondria exposed elevated calcium concentration. Another important mechanism of action seems to be the inhibition of magnesium-dependent enzymes by competing for the same binding site. This last way of action would cause the inhibitory activity of the enzyme inositol monophosphatase and the modulation of G-proteins and biphosphate 3-prime-nucleotidase (BPNT1). At least Li seems to be act in the regulation of gene expression for growth factors and neuronal plasticity with downstream signal transduction cascades, including the inhibitory activity of glycogen synthetase kinase 3 (GSK3) and protein kinase C (PKC) [5,97].
Effect of pulsed millisecond current magnetic field on the proliferation of C6 rat glioma cells
Published in Electromagnetic Biology and Medicine, 2019
Wenjun Xu, Jinru Sun, Yangjing Le, Jingliang Chen, Xiaoyun Lu, Xueling Yao
Since ions inside and outside the cell membrane are different in excitable tissues, such as the nuclei of muscles, there is a certain potential difference inside and outside the membrane, which is referred to as the membrane potential. The resting potential of different cells is variable. The potential of human neurons is −86 mV and is −90 to −80 mV for ventricular myocytes; for sinoatrial node cells, it is −70 to 40 mV, and is generally maintained at around −70 mV (Cifra et al., 2011). From the perspective of electricity, a living body is a complex volume conductor composed of a myriad of cells. Each cell consists of a cell membrane, a cytoplasm and a nucleus. The extracellular fluid between cells has the same electrical conductivity as the cytoplasm, which is equivalent to resistance, and the low leakage characteristics of the cell membrane can be equivalent to a capacitor (Kotnik et al., 2012). Simulation results show that the cell membrane can be equivalent to a low-pass filter and is a place where weak low-frequency magnetic fields interact (Chenguo et al., 2008). Organelle membranes such as the mitochondrial membrane and nuclear membrane can be equivalent to band-pass filters, and the intermediate frequency component is more likely to pass through the organelle membrane. The opening of calcium channels can also be affected by the ELF magnetic field (Koch et al., 2003; Yan, 2007).