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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).
Organization of Central Respiratory Neurons
Published in Alan D. Miller, Armand L. Bianchi, Beverly P. Bishop, Neural Control of the Respiratory Muscles, 2019
Armand L. Bianchi, Rosario Pásaro
These respiratory medullary neurons are subjected to rhythmic depolarizations and repolarizations. Careful examination of the membrane potential trajectories, especially during the phases when the neurons are inhibited, gives detailed information about the period within the respiratory cycle at which the neurons are alternatively excited and inhibited (reviewed in Reference 11).
Cardiovascular Toxicology
Published in Frank A. Barile, Barile’s Clinical Toxicology, 2019
Conducting cells in the atria are found in the internodal pathways, which distribute the contractile stimulus to atrial muscle cells as the impulse travels from the SA node to the AV node. The ventricular conducting cells include those in the AV bundle and the bundle branches as well as the Purkinje fibers, which distribute the stimulus to the ventricular myocardium. The cells in the conducting system share an important feature: they cannot maintain a stable resting potential. Each time repolarization occurs, the membrane potential again gradually drifts toward a threshold. The rate of spontaneous depolarization varies in the different portions of the conducting system. It is fastest at the SA node, principally because of the constant leaking of Na+ ions in these specialized cells, giving the SA node the distinctive title of cardiac pacemaker.
Hyperoside ameliorates cerebral ischaemic–reperfusion injury by opening the TRPV4 channel in vivo through the IP3-PKC signalling pathway
Published in Pharmaceutical Biology, 2023
Lei Shi, Chenchen Jiang, Hanghang Xu, Jiangping Wu, Jiajun Lu, Yuxiang He, Xiuyun Yin, Zhuo Chen, Di Cao, Xuebin Shen, Xuefeng Hou, Jun Han
First, the rats were sacrificed by CO2 asphyxiation. Then, cerebral vessels were carefully excised from rats under an inverted microscope, fixed in a 10 mL silica gel slot with an average pressure of 85 mmHg, bubbled with PSS containing 95% O2 and 5% CO2, and incubated at a temperature of 37 °C for 1 h. Microelectrodes for the detection of intracellular membrane potential (Em) were applied to vascular endothelial smooth muscle cells (VSMCs) of the CBA. A glass microelectrode (40–80 MΩ, filled with 3 mol/L KCl) was inserted into each VSMC to measure the trends in the intracellular membrane potential (Em) value. The potential difference and interference (50 Hz) were recorded using a conventional high-impedance amplifier and selectively moved aside. The values of Em were monitored and analysed using a MacLab system connected to Chart 5 software. Hyperpolarization of VSMC membranes was recorded as soon as the negative resting membrane potential increased evidently (Petersen 2017).
Alpha adrenergic receptors have role in the inhibitory effect of electrical low frequency stimulation on epileptiform activity in rats
Published in International Journal of Neuroscience, 2023
Mahmoud Rezaei, Nooshin Ahmadirad, Zahra Ghasemi, Amir Shojaei, Mohammad Reza Raoufy, Victoria Barkley, Yaghoub Fathollahi, Javad Mirnajafi-Zadeh
About five minutes after applying high-K+ aCSF, EA started, and CA1 pyramidal cells fired spontaneous action potentials that were recorded intracellulary. Applying high-K+ aCSF depolarized the membrane potential. The changes in baseline membrane potential, but not the changes in membrane voltage due to occurrence of an action potential, were measured during three phases: (a) before EA initiation for 5 min (before EA), (b) from EA initiation to start of high-K+ aCSF washout, which lasted 15 min (EA to washout), and (c) after starting high-K+ aCSF washout for 10 min (after washout) (Figure 1a). In the HK group, the mean value of membrane potential before EA starting was −64.67 ± 0.47 mV. From EA to washout, the membrane potential slowly depolarized and reached −47.17 ± 0.41 mV. After high-K+ aCSF washout, the membrane potential gradually hyperpolarized, and its average was −48.68 ± 0.69 mV.
Mitochondrial Pro-Apoptotic Properties of Sinularia compressa from Persian Gulf against Breast Cancer Cells and Its Chemical Composition
Published in Nutrition and Cancer, 2022
Pardis Mohammadi Pour, Afsaneh Yegdaneh, Mahmoud Aghaei, Fatemeh Kazemi, Mustafa Ghanadian
Mitochondrial -dependent apoptosis is also known as the intrinsic pathway of apoptosis. Some proteins in the inner part of the mitochondrial membrane due to swelling may cause membrane pores or increase the permeability of the mitochondrial membrane, which causes the leaking of apoptotic effectors (37). Indeed, depolarization of the membrane potential, and subsequent rupture of the outer membrane, lead to the release of intermembrane space proteins. Figure 4 clearly showed that SCE induced apoptosis in MCF-7 and MDA-MB231 cells concomitant with loss of ΔΨm, suggesting that it exert apoptosis through the mitochondrial pathway. This mitochondrial dysfunction is possibly related to intracellular ROS overproduction (38). Mitochondria are the location in which most of the reactive species are produced. They can target nearby mtDNA leading to impair mtRNA transcription of proteins, and loss to mitochondrial membrane potential (37)