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Membrane Potentials: The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or Organelles membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).

Ion Channels

JoVE 10722

Ion channels maintain the membrane potential of a cell. For most cells, especially excitable ones, the inside has a more negative charge than the outside of the cell, due to a greater number of negative ions than positive ions. For excitable cells, like firing neurons, contracting muscle cells, or sensory touch cells, the membrane potential must be able to change rapidly moving from a negative membrane potential to one that is more positive. To achieve this, cells rely on two types of ion channels: ligand-gated and voltage-gated. Ligand-gated ion channels, also called ionotropic receptors, are transmembrane proteins that form a channel but which also have a binding site. When a ligand binds to the surface, it opens the ion channel. Common ionotropic receptors include the NMDA, kainite, and AMPA glutamate receptors and the nicotinic acetylcholine receptors. When a ligand, like glutamate or acetylcholine, binds to its receptor it allows the influx of sodium (Na+) and calcium (Ca++) ions into the cells. The positive ions, or cations, follow down their electrochemical gradient, moving from the more positive extracellular surface to the less positive (more negative) intracellular surface. This changes the membrane potential near the receptor, which can then activate nearby voltage gated ion channels to propagate the change in membrane potential throughout the cell

 Core: Cell Signaling

Imaging Membrane Potential with Two Types of Genetically Encoded Fluorescent Voltage Sensors

1Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, 2Center for Functional Connectomics, Korea Institute of Science and Technology, 3College of Life Sciences and Biotechnology, Korea University, 4Advanced Institutes of Convergence Technology

JoVE 53566

 Neuroscience

Whole-cell Patch-clamp Recordings of Isolated Primary Epithelial Cells from the Epididymis

1School of Life Science and Technology, ShanghaiTech University, 2Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, 3University of Chinese Academy of Sciences, 4Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University

JoVE 55700

 Developmental Biology

Measurement of Extracellular Ion Fluxes Using the Ion-selective Self-referencing Microelectrode Technique

1Department of Dermatology, Institute for Regenerative Cures, University of California, Davis, 2Departamento de Biologia, Centro de Biologia Molecular e Ambiental, Universidade do Minho, 3Department of Neurology and Center for Neuroscience, University of California, Davis Imaging of Dementia and Aging Laboratory, 4Department of Ophthalmology, Institute for Regenerative Cures, University of California, Davis

JoVE 52782

 Biology

The Use of Magnetic Resonance Spectroscopy as a Tool for the Measurement of Bi-hemispheric Transcranial Electric Stimulation Effects on Primary Motor Cortex Metabolism

1Department of Psychology, University of Montréal, 2Montreal Neurological Institute, McGill University, 3Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota

JoVE 51631

 Neuroscience

Transcranial Direct Current Stimulation for Online Gamers

1Department of Radiology, Yeouido St. Mary's Hospital, College of Medicine, The Catholic University of Korea, 2Department of Radiology, Incheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea, 3Department of Brain and Cognitive Sciences, Ewha W. University, 4Department of Biomedical Engineering, The City College of New York, 5Department of Neurology, Incheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea

Video Coming Soon

JoVE 60007

 JoVE In-Press

Improving the Accuracy of Flow Cytometric Assessment of Mitochondrial Membrane Potential in Hematopoietic Stem and Progenitor Cells Through the Inhibition of Efflux Pumps

1Ruth L. and David S. Gottesman Institute for Stem Cell and Regenerative Medicine Research, Albert Einstein College of Medicine, 2Departments of Cell Biology and Stem Cell Institute, Albert Einstein College of Medicine, 3Department of Medicine, Albert Einstein College of Medicine, 4Albert Einstein Cancer Center and Diabetes Research Center, Albert Einstein College of Medicine

JoVE 60057

 Biology

Local Field Fluorescence Microscopy: Imaging Cellular Signals in Intact Hearts

1School of Natural Sciences, University of California, Merced, 2Centro de Investigaciones Cardiovasculares, Universidad de la Plata and Conicet, 3Facultad de Ingenieria, Universidad Nacional de Entre Rios, 4Department of Physiology, Midwestern University, 5School of Engineering, University of California, Merced

JoVE 55202

 Biology
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