The cardiac myocyte: excitation and contraction
Neil Herring, David J. Paterson in Levick's Introduction to Cardiovascular Physiology, 2018
Membrane potentials are the result of differences in ion concentrations across the cell membrane and the pres-ence of ion-conducting channels in the membrane. The ion channels have been characterized by patch clamping, in which a tiny patch of cell membrane is sucked onto the end of a micropipette and the electrical current through the channels in the patch is recorded (Figure 4.3). By applying different ions, potentials and blocking agents to the patch, specific ion channels can be identified. Cardiac myocytes express three classes of cation-conducting channel, namely K+-, Na+- and Ca2+-selective channels, with many subtypes in each group. Channel selectivity is not absolute; for exam-ple, a ‘potassium channel’ has a K+/Na+ permeability ratio of ~100:1. Most of these channels can flip repeatedly between open and closed states, and the probability that one state predominates depends on the membrane potential and other factors.
Paper 2 Answers
James Day, Amy Thomson, Tamsin McAllister, Nawal Bahal in Get Through, 2014
Generation of an action potential: Above threshold potential, voltage-gated sodium channels open allowing rapid sodium influx into the cell. Membrane potential rises to +30 mV.Voltage-gated sodium channels close and potassium channels open. Potassium ions move out of the cell down their concentration gradient. Membrane potential drops again; this is repolarization.Membrane potential overshoots below resting membrane potential; this is hyperpolarization.Na+/K+−ATPase pump pumps sodium ions back out of the cell and potassium ions back into the cell to restore resting membrane potential.
Physiology of Excitable Cells
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
The presence of a membrane potential allows electrical communication between cells. For example, a motor nerve, when activated in the spinal cord, relays this information along the axon and releases transmitters by a progressive and propagated reversal of membrane potential. Skeletal muscle contraction is produced by a propagated change in membrane potential spreading over the cell, precipitating the release of calcium from intracellular stores. Afferent nerves are activated by special sense organs and transmit this information by electrical axonal activation and release of neurotransmitters, altering the membrane potential and function of central nervous system cells. In the heart, regular changes in the muscle cell ionic permeability and potential produce cardiac autorhythmicity. In all these examples, alterations in the membrane potential lead to communication between cells.
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).
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.
Efficient simulations of stretch growth axon based on improved HH model
Published in Neurological Research, 2023
Xiao Li, Xianxin Dong, Xikai Tu, Hailong Huang
Where 9] are the maximum conductance for sodium, potassium and leakage currents, respectively. 10] are the corresponding equilibrium membrane potentials after the resting membrane potential is decreased below (−70 mV).
Related Knowledge Centers
- Lipid Bilayer
- Protein
- Transmembrane Protein
- Cell Membrane
- Muscle Cell
- Cell
- Ion
- Ion Transporter
- Ion Channel
- Neuron