A model for understanding membrane potential using springs

2005 ◽  
Vol 29 (4) ◽  
pp. 204-207 ◽  
Author(s):  
David L. Cardozo
Keyword(s):  
Membrane Potential ◽  
Simple Model ◽  
Cellular Membrane ◽  
Equilibrium Potential ◽  
Ionic Conductance ◽  
Similar Form ◽  
Ionic Equilibrium ◽  
Ionic Conductances ◽  
The Relationship

In this report, I present a simple model using springs to conceptualize the relationship between ionic conductances across a cellular membrane and their effect on membrane potential. The equation describing the relationships linking membrane potential, ionic equilibrium potential, and ionic conductance is of similar form to that describing the force generated by a spring as a function of its displacement. The spring analogy is especially useful in helping students to conceptualize the effects of multiple conductances on membrane potential.

scholarly journals Mechanisms of Anion and Cation Permeations in the Resting Membrane of a Barnacle Muscle Fiber

1971 ◽  
Vol 57 (4) ◽  
pp. 408-434 ◽  
Author(s):  
S. Hagiwara ◽  
K. Toyama ◽  
H. Hayashi
Keyword(s):  
Membrane Potential ◽  
Muscle Fiber ◽  
Ion Permeation ◽  
Monovalent Cations ◽  
Barnacle Muscle ◽  
Anion Permeation ◽  
Current Voltage ◽  
Ionic Conductances ◽  
The Relationship ◽  
Barnacle Muscle Fiber

The resting membrane of a barnacle muscle fiber is mostly permeable to cations in a solution of pH 7.7 whereas it becomes primarily permeable to anions if the pH is below 4.0. Mechanisms of ion permeation for various monovalent cations and anions were investigated at pH 7.7 and 3.9, respectively. Permeability ratios were obtained from the relationship between the membrane potential and the concentration of the test ions, and ionic conductances from current-voltage relations of the membrane. The permeability sequence for anions (SCN > I > NO3 > Br > ClO3 > Cl > BrO3 > IO3) was different from the conductance sequence for anions (Br, Cl > ClO3, NO3 > SCN). In contrast, the permeability and conductance sequences were identical for cations (K > Rb > Cs > Na > Li). The results suggest that anion permeation is governed by membrane charges while cation permeation is via some electrically neutral mechanism.

Ionic conductances of monkey solitary cone inner segments

1994 ◽  
Vol 71 (2) ◽  
pp. 656-665 ◽  
Author(s):  
T. Yagi ◽  
P. R. Macleish
Keyword(s):  
Membrane Potential ◽  
Potassium Current ◽  
Time Course ◽  
Reversal Potential ◽  
Light Response ◽  
Membrane Properties ◽  
Equilibrium Potential ◽  
Ionic Conductances ◽  
Voltage Dependent ◽  
Tetraethylammonium Ions

1. The membrane properties of cone inner segments dissociated enzymatically from monkey retina were studied under voltage-clamp conditions using patch pipettes in the whole-cell clamp configuration. 2. A noninactivating, voltage-gated calcium current was evoked at potentials positive to -60 mV and peaked between -30 and -20 mV when barium was substituted for calcium. Cadmium (50 microM) but not nickel (50 microM) blocked the current. 3. A large calcium-activated anion current (IAn) was observed when the membrane potential was set to a level between -60 and 30 mV. The reversal potential of IAn was 0 mV with chloride as the sole anion and about -30 and -40 mV when methanesulfonate and D-aspartate, respectively, replaced intracellular chloride to set the equilibrium potential for chloride at -50 mV. IAn inactivated and oscillated when the membrane potential was maintained at depolarized levels, contrary to calcium-activated anionic currents seen in photoreceptors of other species. 4. A sustained-type potassium current was activated by depolarizations positive to -50 mV. The time course of activation and deactivation were voltage dependent. This potassium current was partially blocked by 20 mM tetraethylammonium ions. 5. A transient potassium current was activated by depolarizations positive to -20 mV. This current was blocked by 4-aminopyridine (2 mM) and inactivated with a time constant of approximately 500 ms. The amplitude in response to voltage steps to 45 mV was decreased by prepulses to voltages more positive than -30 mV. 6. Hyperpolarization negative to -65 mV activated an inward current that was completely blocked by external cesium (10 mM). The reversal potential suggested a conductance mechanism permeable to both sodium and potassium ions. 7. A calcium-activated potassium current, which was found in salamander photoreceptors, was not detected. 8. The presence of these conductances is expected to influence the membrane potential and the time course of the light response in monkey cones.

scholarly journals Contractile activation phenomena in voltage-clamped barnacle muscle fiber.

1978 ◽  
Vol 71 (5) ◽  
pp. 467-488 ◽  
Author(s):  
C Caputo ◽  
R Dipolo
Keyword(s):  
Membrane Potential ◽  
Equilibrium Potential ◽  
Tension Development ◽  
Barnacle Muscle ◽  
Time Integral ◽  
A Value ◽  
Tension Time ◽  
Contractile Activation ◽  
The Relationship ◽  
Barnacle Muscle Fibers

Tension development in voltage-clamped barnacle muscle fibers occurs with depolarizing pulses so small as not to activate the potassium and calcium conductance systems. Peak tension and the tension time integral appear to be graded by both amplitude and duration of the depolarizing pulses. Subthreshold depolarizing conditioning pulses shorter than 500 ms potentiate the response to a given test pulse. This effect diminishes and reverts when the duration of the conditioning pulse is increasingly prolonged. The relationship between fiber membrane potential and tension developed in response to depolarizing pulses is described by an S-shaped curve. The tension saturates at a membrane potential of about +10 mV (inside positive). For a given pulse duration the saturation value remains constant even when the fiber interior reaches a value of +230 mV, which is well above what may be estimated to be the equilibrium potential of calcium ions (Eca = +120). In the presence of 5 mM external procaine, the shape of the tension-potential curve changes; the maximum value tension besides being diminished is not sustained by falls when the potential approaches the estimated value for Eca. These results suggest that under physiological conditions the contractile activator is probably released from an internal store, and that the calcium entering the fiber as inward current does not play a direct major role in contractile activation.

Calcium channels and excitation–contraction coupling in cardiac cells. I. Two components of contraction in guinea-pig papillary muscle

1987 ◽  
Vol 65 (9) ◽  
pp. 1821-1831 ◽  
Author(s):  
E. Honoré ◽  
M. M. Adamantidis ◽  
B. A. Dupuis ◽  
C. E. Challice ◽  
P. Guilbault
Keyword(s):  
Membrane Potential ◽  
Guinea Pig ◽  
Papillary Muscle ◽  
Cardiac Cells ◽  
Resting Membrane Potential ◽  
Tonic Component ◽  
Contraction Coupling ◽  
Rich Solution ◽  
The Relationship ◽  
Guinea Pig Atria

Biphasic contractions have been obtained in guinea-pig papillary muscle by inducing partial depolarization in K+-rich solution (17 mM) containing 0.3 μM isoproterenol; whereas in guinea-pig atria, the same conditions led to monophasic contractions corresponding to the first component of contraction in papillary muscle. The relationships between the amplitude of the two components of the biphasic contraction and the resting membrane potential were sigmoidal curves. The first component of contraction was inactivated for membrane potentials less positive than those for the second component. In Na+-low solution (25 mM), biphasic contraction became monophasic subsequent to the loss of the second component, but tetraethylammonium unmasked the second component of contraction. The relationship between the amplitude of the first component of contraction and the logarithm of extracellular Ca2+ concentration was complex, whereas for the second component it was linear. When Ca2+ ions were replaced by Sr2+ ions, only the second component of contraction was observed. It is suggested that the first component of contraction may be triggered by a Ca2+ release from sarcoplasmic reticulum, induced by the fast inward Ca2+ current and (or) by the depolarization. The second component of contraction may be due to a direct activation of contractile proteins by Ca2+ entering the cell along with the slow inward Ca2+ current and diffusing through the sarcoplasm. These results do not exclude the existence of a third "tonic" component, which could possibly be mixed with the second component of contraction.

Sulu-Sulawesi Seas Patrol: Lessons from the Malacca Straits Patrol and Other Similar Cooperative Frameworks

2018 ◽  
Vol 33 (4) ◽  
pp. 799-826 ◽  
Author(s):  
Hadyu Ikrami
Keyword(s):  
Best Practices ◽  
The Philippines ◽  
Maritime Security ◽  
The Other ◽  
Similar Form ◽  
Security Cooperation ◽  
Sulu Sea ◽  
Straits Of Malacca ◽  
Maritime Strategy ◽  
The Relationship

Abstract On 19 June 2017, Indonesia, Malaysia, and the Philippines launched the Sulu-Sulawesi Seas Patrol (SSSP), a framework of maritime security cooperation aimed at protecting the Sulu Sea and Sulawesi (Celebes) Sea from maritime crimes. The three nations had announced that their cooperation might be modelled on the Malacca Straits Patrol (MSP), a similar form of cooperation between Indonesia, Malaysia, Singapore, and Thailand to safeguard the Straits of Malacca and Singapore. This article primarily compares both cooperative frameworks, and argues that the SSSP should be modelled on the MSP, subject to certain conditions. Where there are insufficient best practices in the MSP, this article contrasts the SSSP with other similar cooperative frameworks, including the Combined Maritime Forces and the ECOWAS Integrated Maritime Strategy. In addition, this article also discusses the relationship between the SSSP and MSP on one hand, and the ASEAN maritime security mechanisms on the other hand.

The Tensile Property of the SPF/Cotton Blended Yarn

2011 ◽  
Vol 321 ◽  
pp. 192-195
Author(s):  
Qing Bin Yang ◽  
Xiao Yang
Keyword(s):  
Experimental Data ◽  
Simple Model ◽  
Tensile Property ◽  
Cotton Fibers ◽  
Blended Yarn ◽  
The Difference ◽  
The Relationship

In order to analysis the relationship between the strength and elongation and the blended ratio of SPF/Cotton blended yarn, the strength and elongation of SPF /cotton blended yarn with different blended ratio were measured and compared with the simple model. The results indicated that For the SPF/cotton blended yarn, the difference between the experimental data and the model value is remarkable because of the high cohesion of the cotton fibers.

Beta-adrenergic actions on membrane electrical properties of dissociated smooth muscle cells

1988 ◽  
Vol 254 (3) ◽  
pp. C423-C431 ◽  
Author(s):  
H. Yamaguchi ◽  
T. W. Honeyman ◽  
F. S. Fay
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Electrical Properties ◽  
Smooth Muscle Cells ◽  
Input Resistance ◽  
Muscle Cells ◽  
Resting Potential ◽  
Equilibrium Potential ◽  
Dependent Manner ◽  
Beta Adrenergic

Studies were carried out to determine the effects of the beta-adrenergic agent, isoproterenol (ISO), on membrane electrical properties in single smooth muscle cells enzymatically dispersed from toad stomach. In cells bathed in buffer of physiological composition, the average resting potential was -56.4 +/- 1.4 mV (mean +/- SE, n = 35). The dominant effect of exposure to ISO was hyperpolarization. The hyperpolarization was apparent in all cells studied and averaged 11.6 +/- 1.2 mV (n = 27). In the majority of the cells, hyperpolarization was accompanied by a decreased input resistance (Rin). Often the change in resistance appeared to lag behind the change in membrane potential. The lack of coincident changes in membrane potential and resistance may reflect a superposition of the outward rectification properties of the membrane on beta-adrenergic-induced increases in ionic conductance. In about half of the cells, an initial small depolarization (3.1 +/- 0.3 mV, n = 14) was accompanied by a small but distinct increase in Rin (12 +/- 2.5%). When membrane potential was made more negative than the estimated equilibrium potential for K+ (EK) by injection of current, ISO also produced biphasic effects, an initial hyperpolarization which reversed to a sustained depolarization to a value (-90 mV) near the estimated EK. The hyperpolarization by ISO could be diminished in a time-dependent manner by previous exposure to ouabain. The inhibition by ouabain, however, appeared to be a fortuitous result of glycoside-induced positive shifts in EK. These observations indicate that the dominant electrophysiological effect of beta-adrenergic stimuli is to hyperpolarize the cell membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of intracellular potassium and sodium injections on the inhibitory postsynaptic potential

1964 ◽  
Vol 160 (979) ◽  
pp. 181-196 ◽  
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Cell Membrane ◽  
Direct Evidence ◽  
Equilibrium Potential ◽  
Ionic Mechanism ◽  
Half Time ◽  
Intracellular Potassium ◽  
Postsynaptic Potential ◽  
Almost All

Two barrels of double microelectrodes have been filled with different salts so that the electrophoretic injection of Na + and K + ions could be investigated in alternating sequence on the same motoneuron in the cat spinal cord. The effects of these injections on the mechanism generating the IPSP were evaluated by determining the equilibrium potential for the IPSP (the E IPSP ), i. e. the membrane potential at which the IPSP is zero. Such determinations have been made every 5 to 10 s after ion injections and have provided the most direct evidence of the ionic mechanism generating the IPSP . Comparison of the Na + and K + ion injections shows that the former injection always displaced the E IPSP much farther in the depolarizing direction and that recovery was much slower, with a half-time of 70 to 120 s, in contrast to about 20 s after the K + injection. In the discussion and evaluation of these results it was postulated that almost all of the displacement of the E IPSP in the depolarizing direction was due to the increased intracellular Cl - concentration, the (Cl - ) i . Under normal conditions a high (Cl - ) i declines by diffusional exchange across the cell membrane with a half-time of about 20 s, but this decline is much slower when the internal potassium is depleted. An explanation of this difference will be given in the following paper.

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