China
Africa
Explore chapters and articles related to this topic
Elements of Bioelectricity
Published in Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu, Interdisciplinary Engineering Sciences, 2020
Ashutosh Kumar Dubey, Amartya Mukhopadhyay, Bikramjit Basu
The above equation is called as the Goldman–Hodgkin–Katz (GHK) current equation.4 Here, Vm and PX are the membrane potential and the permeability coefficient of the ion X, respectively. This equation is simply based on Ohm's law, because the current and voltage are directly proportional in this case. If the current of the single ionic species is set to zero, then the above equation reduces to Nernst equation, giving the equilibrium potential for that particular ionic species. Nernst equation is also called the reversal potential, for the cations and anions. For the cations, if the potential of the membrane is less positive as compared to the reversal potential, the current of the cation will be directed inwards. If it is more positive as compared to the reversal potential, the current of cations will be directed outwards. Therefore, the direction of the ionic current, changes at reversal potential. Similar phenomenon is true for the case of anions as well.
X-Nuclei MRI and Energy Metabolism
Published in Guillaume Madelin, X-Nuclei Magnetic Resonance Imaging, 2022
Equilibrium potential and Nernst equation. When ions are in electrochemical equilibrium, an equilibrium potential for these ions is created across the membrane. For any ion A with extracellular concentration [A]ex and intracellular concentration [A]in, the equilibrium potential can be calculated using the Nernst equation:Eeq=RTzFIn[A]ex[A]in with R= 8.314463 JK-1mol-1 the universal gas constant, T the absolute temperature (in K), z the electric charge of the ion (+1 for Na+andK+,+2 forCa2+, - 1 for Cl-), and F= 96485.33212 Cmol-1 the Faraday constant. The average Nernst equilibrium potential values of the main electrolytes are summarized in Table 2.2. This Nernst (also sometimes called reversal) potential for a specific ion is therefore the membrane potential at which there is no net (overall) flow of that ion from one side of the membrane to the other, and is equivalent to equilibrium potential for ideal single-ion systems only. A change in membrane potential, or membrane permeability (for example when ion channels open), will provoke a flux of ion.
Computational modelling of mechano-electric feedback and its arrhythmogenic effects in human ventricular models
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Yongjae Lee, Barış Cansız, Michael Kaliske
SACs are one of the physiological mechanisms behind MEF in cardiac tissue (Kohl et al. 1999; Hu and Sachs 1997). Since SACs were first demonstrated via experiments with amphibian ventricle (Lab 1978), there has been a considerable progress in research on MEF with developments of mathematical models for SACs. Sachs (1994) firstly attempted to incorporate SACs associated with sarcomere length as a measure of strain into the guinea-pig ventricular cell model (Noble 1992), whose results agreed well with the experimental observations. The effect of SACs observed in the experiments was reformulated by Sachs (1994) in terms of the fibre stretch, the maximum channel conductance and the reversal potential. Panfilov et al. (2005) have incorporated this mathematical model for SACs into an electromechanical model, where they found that the mechanical deformation results in automatic pacemaking activity via SACs. Moreover, mechanically induced arrhythmia was examined with recruitment of two types of SACs, cation-nonselective and potassium-selective channels by using a purely electrophysiological model (Trayanova et al. 2010) and by using a coupled electromechanical model (Jie et al. 2010). Lunze et al. (2010) added a term for open channel probability that depends on the myocardial strain to the model, which was incorporated into a 3 D human ventricular model within a human torso geometry and 12-lead electrocardiogram (ECG) was computed. Costabal et al. (2017) hypothesized that MEF may occur by additional deformations due to inertia effects and studied the alteration of wave dynamics via MEF using electromechanical models.
Event-triggered consensus control for stochastic multi-agent systems under state-dependent topology
Published in International Journal of Control, 2021
Chengbo Yi, Jianwen Feng, Chen Xu, Jingyi Wang, Yi Zhao
Furthermore, if the information transmissions, embellished on each nodes i, j, is depended on the states , the graph is translated into a state-dependent directed graph denoted as . Applying the positive function to describe the connections, where , correspondingly, the weighted adjacency matrix can be defined as . The function usually comes from some learning rules. For instants, from neural networks, the simplest form to use is the basic Hebb rule, in which the strength of the connections depends on the neural activities, i.e. on the states . In Bogojeska et al. (2014), the modified rule is proposed, where , called reversal potential, is a constant and for . In this paper, more general cases are considered that the state-dependent function is only supposed to be symmetric, of which an assumption will be given in the subsequent.
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 parameters for the intermediate scale are as follows. The specific membrane capacitance , resting potential , cytoplasm resistivity , specific leak conductance and leak reversal potential [24]. We let the model be confined to a cylindrical geometry with a length of and a diameter of . The cylinder is compartmentalized into sub-cylinders of equal length and diameter. The root node is ignited by a current injection of .