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Introduction: Background Material
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
All living cells have a surrounding envelope referred to as the cell membrane, or plasma membrane. Animal cells are eukaryotic, that is, they have a well-developed nucleus and other membrane-bounded organelles, which are cell elements that perform some specialized functions. Figure 1.1 illustrates a typical eukaryotic cell and some of its organelles. The part of the cell that is outside the nucleus and bounded by the cell membrane is the cytoplasm. The cytosol, or intracellular fluid, is the liquid part of the cytoplasm, exclusive of organelles. It consists of a complex mixture of substances that are dissolved or suspended in water. The cell membrane is discussed in considerable detail in Sections 2.1 and 2.2. The following cell organelles are particularly relevant for our purposes.
Physiological basis and concepts of electromyography
Published in Kumar Shrawan, Mital Anil, Electromyography in Ergonomics, 2017
Part of a muscle fiber is represented in the upper part of Figure 2.2. The fiber is surrounded by a cell membrane which divides the intracellular fluid from the interstitial fluid. A measurement system comprising an electrode and a voltage display indicates a transmembrane potential of approximately −75 mV. The symbols for the ions in the upper part of Figure 2.2 vary in size as a sign of the unequal distribution of the relevant ions between the intracellular and the interstitial phase. The quantitative information on typical ion concentrations is to be found in the table in the lower part of Figure 2.2. The composition of the intracellular fluid is characterized by a high concentration of potassium cations (K+) and protein anions (A−) whereas the interstitial fluid is rich in sodium cations (Na+) and chloride anions (Cl−). (The concentration of further ions such as calcium, magnesium, bicarbonate and phosphate is not provided here since these substances only have a slight influence on the levels of the membrane potentials and on the electrical phenomena during the development of the action potential at the membranes.) Approximate ratios of the concentrations (internal : external) are provided in the right-hand column of the table in Figure 2.2. They range between 1:30 for Cl− and 40:1 for K+. Negatively charged protein ions (A−) are only found inside the cells. Their concentration in the extracellular space is negligible.
The impact of electric fields on cell processes, membrane proteins, and intracellular signaling cascades
Published in Ze Zhang, Mahmoud Rouabhia, Simon E. Moulton, Conductive Polymers, 2018
In the equivalent circuit method, we consider electrolyte solutions—such as the interstitial fluid and the intracellular fluid—a resistor. The interface that does not allow charge to pass is considered a capacitor, such as the nonpolarizable electrode and the cell membrane. As a simple example, a uniform cell suspension in culture medium is modeled using an equivalent circuit (Figure 8.7). Cmem is the capacitance of the cell membrane, Rin is the resistance of the intracellular fluid, and Rex is the resistance of the extracellular fluid. Human blood closely resembles this example. The distribution of the electrical signal can thus be calculated using the impedance information and the voltage division rule.
Features extraction of MRI image using complex network with low computational complexity to distinguish inflammatory lesions from tumors in the human brain
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2023
Trong Thanh Han, Tung Nguyen Duy, Lam Nguyen Dang Son, Hinh Nguyen Van, Tuan Do Trong, Dung Nguyen Viet, Dung Nguyen Tuan, Luu Vu Dang
Diffusion – Weighted Imaging (DWI) as in Figure 2 is used to evaluate the diffusion of water molecules within an organ. Normally, extracellular fluid diffuses freely in all directions (no diffusion restriction), while intracellular fluid is diffusion restricted. Newly damaged areas cause cellular oedema, resulting in less extracellular fluid, increased intracellular fluid, causing limited diffusion of water. If a structure is diffusely restricted, meaning that there is cellular oedema, the hyperintense DWI image is white. If tissue is not diffusely restricted, there is no cellular oedema, then DWI is hypointense and it is black. Therefore, DWI is a very effective method for detecting cellular swelling (ischaemia, for instance) and oedema. This is one of the typical signs of inflammation.
Cell wall components, cell morphology, and mechanical properties of peach slices submitted to drying
Published in Drying Technology, 2020
Chunju Liu, Jiaxin Liu, Dajing Li, Chunquan Liu, Zhongyuan Zhang, Ning Jiang, Liying Niu, Min Zhang, Jinjin Cheng
At the macroscopic level, fruits and vegetables are viscoelastic systems that exhibit a combination of elastic and viscous behavior under mechanical loading.[17–19] In plants, viscoelasticity is dependent on structural changes at the cellular level.[20,21] These changes depend on cell turgor pressure (the force exerted on the cell membrane by intracellular fluid), cell–cell adhesion (determined by the middle lamella and plasmodesmata), and cell wall rigidity (determined by cellulose and hemicellulose). Both cell turgor pressure and primary cell wall strength are determined by cellulose and hemicellulose that are related to the elastic properties.[22–25] The cell wall structure is considered a continuous matrix made up of cellulose–hemicellulose network, pectin matrix, structural proteins, and other non-polysaccharide components.[26,27] Pectin is a complex polysaccharide in the cell wall, which plays the role of a hydrophilic filler to determine cell wall porosity.[28,29] Pectin has an effect on cell wall diffusivity as well as on cell wall water uptake and cell wall swelling. Cross-linking of pectin and hemicellulose in the cell wall will increase the structural strength and complexity of the cell wall.[30] The contents and thickness of cellulose determine cell wall rigidity and hardness.[21,31–33]
Optimization of the electrode configuration of electrical impedance myography for wearable application
Published in Automatika, 2020
J. N. Wang, H. Y. Zhou, Y. M. Gao, J. J. Yang, Ž. Lučev Vasić, M. Cifrek, M. Du
The principle of EIM based on the four-electrode method for muscle fatigue detection is analysed in detail according to the three-element model of biological tissue [11–13]. The three-element model is considered to be connected in series by the resistance of intracellular fluid Ri and the capacitance of cell membrane Cm, and then parallel with the resistance of extracellular fluid Re according to dielectric properties of tissues [14]. Regardless of the serial or parallel array of the four-electrode method, both circuit systems adopt the excitation mode of a constant current source. The excitation electrodes are denoted 1 and 4, while the measuring electrodes are denoted 2 and 3. Z1, Z2, Z3, and Z4 are the contact impedances produced by the contact between the electrodes (1, 2, 3, and 4) and muscle tissue in the theoretical models of the four-electrode method. Figure 2(a) illustrates equivalent circuit model A of the four-electrode method in serial array, while Figure 2(b) demonstrates equivalent circuit model B of the four-electrode method in parallel array.