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Topic: Membrane potential

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In the News (Fri 21 Jun 19)

  Membrane Pore: Reviews
We propose a hypothesis that an increase in the spontaneous curvature of the organelle's membrane leads to an increase in membrane tension and thus to the vacuole's rounding, severing of the radial arms from the vacuole, and opening of the pore.
The advantages and potential pitfalls of the various approaches are discussed, with some emphasis on the use of cyt c-GFP fusions and the determination of the characteristics of the putative outer membrane pore through which cyt c and other mitochondrial proteins with proapoptotic functions may pass.
The propargylamine moiety is responsible for the increase in the mitochondrial family of Bcl-2 proteins, prevention in the fall in mitochondrial membrane potential, prevention of the activation of caspase 3, and of translocation of glyceraldehyde-3-phosphate dehydrogenase from the cytoplasm to the nucleus.
lansbury.bwh.harvard.edu /membrane_pore_reviews.htm   (14874 words)

 Membrane potential - Wikipedia, the free encyclopedia
Membrane potential (or transmembrane potential or transmembrane potential difference or transmembrane potential gradient), is the electrical potential difference (voltage) across a cell's plasma membrane.
Action potentials are transient spikes in membrane potential characterized by initiating membrane potential changes that start the transmembrane flow of charged solutes through voltage-gated ion channels which in turn results in new membrane potential changes that ultimately return the membrane potential to the value it had at the start of the spike.
The typical membrane potential of a cell arises from the separation of potassium ions from intracellular immobile anions across the membrane of the cell.
en.wikipedia.org /wiki/Membrane_potential   (3028 words)

 Brain and Behavior (IPHY 3730), University of Colorado at Boulder
The plasma membrane of a nerve cell functions as a barrier between the cytoplasm and the extracellular environment of the cell.
Membrane proteins in a nerve cell have a number of specific functions, such as permitting selective passive of an ion (=ion channel), moving an ion against a concentration gradient (=ion pump), or acting as a receptor which communicates information about events in the immediate environment.
Membrane transport of solute (such as glucose or Na+) is by either diffusion (passive, down a concentration gradient), facilitated diffusion (passive, mediated, down a concentration gradient, or active transport (requiring energy, mediated, but movement against a concentration gradient).
www.colorado.edu /intphys/Class/IPHY3730/03plasmamembrane.html   (1826 words)

Membranes are composed of phospholipids, proteins and carbohydrates arranged in a fluid mosaic structure, as shown in this diagram.
Proteins on the inside surface of cell membranes are often attached to the cytoskeleton and are involved in maintaining the cell's shape, or in cell motility.
Cell membranes are a barrier to most substances, and this property allows materials to be concentrated inside cells, excluded from cells, or simply separated from the outside environment.
www.biologymad.com /cells/cellmembrane.htm   (1771 words)

 Membrane potentials
Membrane potentials are determined primarily by three factors: 1) the concentration of ions on the inside and outside of the cell; 2) the permeability of the cell membrane to those ions (i.e., ion conductance) through specific ion channels; and 3) by the activity of electrogenic pumps (e.g., Na
At the peak of the action potential in a cardiac cell (e.g., ventricular myocyte), the membrane potential is approximately +20 mV.
However, to fully understand how multiple ions affect the membrane potential, and ultimately how the membrane potential changes during action potentials, it is necessary to learn how changes in membrane ion permeability, that is, changes in ion conductance, affect the membrane potential.
www.cvphysiology.com /Arrhythmias/A007.htm   (827 words)

 Bacterial Adhesion Assay   (Site not responding. Last check: 2007-10-26)
Because bacterial attachment is a critical and necessary first step for membrane biofilm formation, the 'biofouling potential' of a membrane can be estimated by determining the relative affinity of selected bacterial strains for the particular membrane(s) of interest.
The degree of bacterial attachment is proportional to the fouling tendency (i.e., the biofouling potential) of that membrane.
In addition, a standard set of 'control' membrane materials is routinely run in parallel with the test membrane sample(s) to account for experimental variation in the assay from one run to the next and to provide base line data with which the test membranes can be compared.
www.micromemanalytical.com /bacAA/bactAA.htm   (1832 words)

 Intracellular Ion Environment and Membrane Electric Potential
In all cases, the rate and extent of ion transport across membranes is influenced not only by the ion concentrations on the two sides of the membrane but also by the voltage (i.e., the electric potential) that exists across the membrane.
The resulting separation of charge across the membrane can be measured by a potentiometer as an electric potential, or voltage, with the right side of the membrane negative (having excess negative charge) with respect to the left (Figure 15-8b).
In plants and fungi, the membrane potential is maintained by the ATP-driven pumping of protons from the cytosol across the membrane.
www.ncbi.nlm.nih.gov /books/bv.fcgi?rid=mcb.section.4055   (2011 words)

Still, the opportunity to acquire a good command of the common mechanisms that underlie phenomena such as synaptic potentials, action potentials, pacemaker potentials, etc., as well as the relative stability of the resting membrane potential, is being missed.
It is then shown that the chemical potential, or free energy per mole, is the potential whose corresponding field may be considered to generate a force responsible for the directed movement of the particles.
The electrical potential difference established across the membrane is the potassium equilibrium potential which depends on the ratio of the concentrations of the ion on both sides of the membrane.
www.fiu.edu /~cuervol/PhysiologicalMechanisms/MembranePotential.htm   (3143 words)

 An Illustrated Discussion of the Membrane Potential Concept
The membrane potential is critical for maintenance of the integrity of the cell membrane including the protein complexes within the lipid bilayer, and for signal transduction in excitable cells such as nerve and muscle.
The equilibrium potential is a consequence of the displacement of positive ions across the membrane.
Some of the positive ions that were separated from their negative counter-ions by the membrane are now back on the same side as their counter-ions, so fewer ion pairs are separated and the membrane is less polarized.
www.ruf.rice.edu /~bioslabs/bios315/mempot1.htm   (1138 words)

 A Brief Introduction to the Brain:Membrane Potential
Electrical signals (receptor potential, synaptic potential and action potential) are all caused by transient changes in the current flow into and out of the neuron, that drives the electrical potential across the plasma membrane away of its resting condition.
The relative excess of positive charges outside and negative charges inside the membrane of a nerve cell at rest is maintained because the lipid bilayer acts as a barrier to the diffusion of ions, and give rise to an electrical potential difference, which ranges from about 60 to 70 mV.
Transient current flow and therefore rapid changes in potential are made possible by ion channel, a class of integral proteins that traverse the cell membrane.
ifcsun1.ifisiol.unam.mx /Brain/mempot.htm   (792 words)

 16 Action Potential   (Site not responding. Last check: 2007-10-26)
Recall that one of the characteristics of graded potentials is that the magnitude of change in membrane potential decreases with distance from the point of stimulation.
Action potentials are only triggered, however, in the downstream region of the axon because the Na channels in the membrane of the upstream region are still in a state of refractoriness.
By the time the channels are in an excitable state, the action potential has moved far enough down the length of the axon that the graded potentials that spread electrotonically are of insufficient strength to elicit an upstream potential.
human.physiol.arizona.edu /sched/cv/wright/16action.htm   (1894 words)

 Plasma Membrane
Membrane potential, function of ion gates (channels) and the conduction of electrical signals along nerve fibers.
As mentioned previously the plasma membrane is composed of a bilayer.
The plasma membrane is assymetric with respect to the lipid distribution.
www.prism.gatech.edu /~gh19/b1510/memtra.htm   (2182 words)

 NS Lecture 14: Membrane Potential   (Site not responding. Last check: 2007-10-26)
is the membrane permeability (in cm/sec) for the indicated ion.
Because the membrane has a finite permeability to most ionic species, the actual electrical PD at any point in time is a compromise between their combined influence.
Biologically relevant changes in membrane potential arise through changes in the permeability of the membrane to the various ions whose concentrations are great enough to make them "players" in defining the electrical status of the cell.
human.physiol.arizona.edu /SCHED/CV/Wright/14membra.htm   (2427 words)

 Membrane Potential 3   (Site not responding. Last check: 2007-10-26)
Remember that the membrane potential is at +62 mV, which means that the electrical force is pushing potassium out of the cell.
The membrane potential of the cell will move to be close to the equilibrium potential of the most permeable ion.
The number of actual ions that move to change the membrane potential of a cell is generally very small so that the concentrations of the ions do not change.
www.austincc.edu /emeyerth/mempot3.htm   (463 words)

 Resting potential - Wikipedia, the free encyclopedia
The resting potential of a cell is the membrane potential that would be maintained if there were no action potentials, synaptic potentials, or other active changes in the membrane potential.
The resting potential is mostly determined by the concentrations of the ions in the fluids on both sides of the cell membrane and the ion transport proteins that are in the cell membrane.
For determination of membrane potentials, the two most important types of membrane ion transport proteins are ion channels and ion pumps.
en.wikipedia.org /wiki/Cell_potential   (593 words)

 D.F. Davey's Teaching Resources - Membrane Potential
The membrane potential is a manifestation of a small separation of charge across the lipid bilayer of the membrane.
Although the membrane potentials observed in cells are less than 1/10th of a volt, the electrical field is very large.
This particular case is very important in many attempts to understand membrane phenomena because the membrane potential is temporarily eliminated from influencing ion movements, merely because it is zero.
www.physiol.usyd.edu.au /daved/teaching/potential.html   (577 words)

 Generation of resting membrane potential -- Wright 28 (4): 139 -- Advances in Physiology Education
is the membrane permeability (in cm/s) for the indicated
membrane permeability to ions is defined by the activity of
on the membrane surface is analogous to the action of a capacitor.
advan.physiology.org /cgi/content/full/28/4/139   (2563 words)

 Biology 202: Membrane Structure & Function
Lipids and Proteins are free to move about (diffuse) in the plane of the membrane and to rotate about an axis perpendicular to the membrane.
are an intrinsic component of the membrane and extend from one side of the lipid bilayer to the other; they cannot be removed without disrupting the membrane.
In (b) water diffuses across the membrane until the difference in height, h, equals the osmotic pressure.
www.sci.sdsu.edu /classes/biology/bio202/TFrey/MembraneStructure.html   (1280 words)

 Ionic basis of the resting membrane potential
This potential difference results from a separation of charge across the cell membrane: there is an excess of positive charges on the extracellular face of the membrane and an excess of negative charges on the inside of the cell membrane.
It should be noted that the small excess of anions at the inner surface of the cell membrane and cations at the outer surface that create the resting potential is negligible relative to the total number of ions in the bulk intracellular and extracellular solutions.
The cell membrane is composed of a mosaic of lipids and proteins.
www.williams.edu /BIMO/liz/LEC2.html   (1753 words)

 Direct and Indirect Actions of Dopamine on the Membrane Potential in Medium Spiny Neurons of the Mouse Neostriatum -- ...
To study the subthreshold potential oscillation, the membrane potentials were digitized at 0.33 kHz.
In all recordings, the membrane was depolarized from the resting potential to the subthreshold level by injection of depolarizing current pulses (intensity 0.3-0.7 nA for 1.5 s every 3 s) to obtain distinct responses induced by administration of DA (indicated by horizontal bars).
Membrane properties and synaptic responses of rat striatal neurons in vitro.
jn.physiology.org /cgi/content/full/87/3/1234   (5933 words)

 FLIPR Membrane Potential Assay Kit
Patch clamping is considered the "gold standard" for measuring membrane potential, but it is too slow and labor intensive to use in a primary screen.
And because the proprietary indicator dye in the Membrane Potential Assay Kit is much less sensitive to temperature changes than DiBAC, plates can be set up ahead of time and stacked for batch runs, making the assay highly amenable to automation.
With the FLIPR Membrane Potential Assay Kit, not only is the reagent much less temperature sensitive than DiBAC it is also less sticky, so there is no need to pre-soak tips, further increasing throughput.
www.moleculardevices.com /pages/reagents/f_mem_kit.html   (592 words)

 Cell membrane potential- first page   (Site not responding. Last check: 2007-10-26)
They are designed to make easier the understanding of the basic principles of generation and spreading of electric potential in excitable cells.
Flow of sodium and potassium ions during an action potential
Here you can simulate how the input through the presynaptic cell generates postsynaptic potential and when it is high enough, the postsynaptic cell starts to fire spikes.
www.emile-21.com /VRML/membPot0.html   (164 words)

 FBR ScienceWorks for ME - Long QT-Resting Membrane Potential
Long QT Syndrome and the Resting Membrane Potential: From Microscopic to Macroscopic is a curricular unit devised by FBR's Dr. Walt Allan, a pediatric neurologist.
In Long QT syndrome, this disturbance is caused by an inherited mutation in a gene that regulates one of the ion channels in heart muscle cells.
An objective of this lab is to demonstrate that the inherited defect in ion channels alters the repolarization phase of the action potential, leading to prolongation of the QT interval and to sudden death in Long QT syndrome.
www.fbr.org /swksweb/lqtrmp.html   (328 words)

 [No title]
An early indicator of the initiation of cellular apoptosis is the collapse of the electrochemical gradient across the mitochondrial membrane.
Our new Mitochondrial Membrane Potential Detection Kit detects the loss in membrane potential by detecting the fluorescence of a unique dye, JC-1 (Figure 3), thus differentiating healthy cells from apoptotic cells.
In apoptotic cells, the mitochondrial membrane collapses and JC-1 disperses throughout the cell, while maintaining its green fluorescent monomeric form..
www.stratagene.com /products/displayProduct.aspx?pid=624   (152 words)

    D. a membrane that exhibits a membrane potential is said to
             outer surface of the membrane
at peak of action potential, polarity is the reverse of
alamo.nmsu.edu /~vlombran/HumanPhysiologyLecture-MembranePotential.html   (1305 words)

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