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Elements of Bioelectricity
Published in Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu, Interdisciplinary Engineering Sciences, 2020
Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu
These membrane proteins contain a movable barrier, which alternatively opens and closes depending upon the voltage across the membrane (voltage gating), mechanical stress across the membrane (mechanical gating), and synaptic signals across the membrane (ligand gating). Gating is the process of opening and closing of the channels in response to particular external or internal stimuli. The selectivity filter gives specificity to the ion channels, that is, a particular class of ions should pass through a particular channel. Mostly, Na+ channels are voltage gated, that is, they open whenever the potential across the membrane changes and in this process Na+ ions are allowed to enter the cells. This contributes to the generation of action potential. The mechanism of flow through Na+ channels is the same as through the open channels. Apart from Na+ channels, K+, Ca2+, proton, and anion (Cl−, HCO3−) channels are also gated.
Electrophysiology
Published in Jay L. Nadeau, Introduction to Experimental Biophysics, 2017
Jay L. Nadeau, Christian A. Lindensmith, Thomas Knöpfel
Along with selectivity, many ion channels also display gating, which means that they are effectively open only in the presence of a stimulus of some kind. Voltage-gated ion channels open in response to a particular transmembrane voltage (“membrane potential”); ligand-gated ion channels open in response to the binding of a chemical species (Figure 15.1). Other types of gating exist as well, such as gating caused by mechanical stress (mechanosensitive channels), temperature, or light (channel rhodopsin).
Short-term Demand Forecasting for Online Car-hailing Services Using Recurrent Neural Networks
Published in Applied Artificial Intelligence, 2020
Alireza Nejadettehad, Hamid Mahini, Behnam Bahrak
GRU was proposed by Cho et al. in 2014 (Cho et al. 2014). It is similar to LSTM in structure but simpler to compute and implement. The difference between a GRU cell and an LSTM cell is in the gating mechanism. It combines the forget and input gates into a single update gate. It also merges the cell state and the hidden state. The function of reset gate is similar to the forget gate of LSTM. Since the structure of GRU is very similar to LSTM, we will not get into the detailed formula. The structure of a GRU cell is shown in Figure 4.
Deep spatio-temporal sparse decomposition for trend prediction and anomaly detection in cardiac electrical conduction
Published in IISE Transactions on Healthcare Systems Engineering, 2022
Xinyu Zhao, Hao Yan, Zhiyong Hu, Dongping Du
Here, t represents time and s indicates spatial location. u(t, s) is the transmembrane potential, is a vector of variables associated with the ion channel conductance (gating variables). c(t, s) is the external stimulus, Cm is the total capacitance, and D is the isotropic diffusion coefficient determined by gap junction resistance, surface-to-volume ratio, and membrane capacitance (Courtemanche et al., 1998). Iion is the summation of 12 different ion channel currents, which are controlled by u(t, s) and with over 70 equations. These equations are compactly represented by in (2), and their detailed expressions as well as model parameters used for the data generation can all be found in (Xie et al., 2002). In reality, the transmembrane potential u(t, s) can often be measured (i.e., observable), but the ion currents Iion and the associate hidden variable are often hard to obtain (i.e., unobservable). Although Iion and are unobservable, it is known that they take into effect on the transmembrane potential within different periods, such as the sodium currents affect the rising of u(t, s) while potassium currents influence its restoration. It is such a phenomenon that motivates the proposed modeling structure in the next section. The CRN model has been popularly used in many studies to simulate both normal heart functions and cardiac disorders such as atrial fibrillation (Harrild & Henriquez, 2000; Xie et al., 2002; Zahid et al., 2016). However, due to its computational complexity, metamodeling techniques are important to reduce computational complexity. The details of the CRN model can be found in (Courtemanche et al., 1998).
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
where is the number of gating particles for the particular ion channel model, and is the exponent of the ith gating variable .