Potentials potassium

Alger, B. E., and Nicoll, R. A. (1980) Epileptiform burst afterhyperpolarization Calcium-dependent potassium potential in hippocampal CA1 pyramidal cells. Science, 210 1122-1124. 

Hyperkalemia This occurs most commonly in patients given IV potassium, but also may occur in patients given oral potassium. Potentially fatal hyperkalemia can develop rapidly and may be asymptomatic. 

Beckett, P. H. T. 1964. Studies on soil potassium. I. Confirmation of the ratio law Measurement of potassium potential. J. Soil Sci. 15 1-8. 

The only antiarrhythmic agent that consistently alters the resting potential of the AV node is adenosine. It apparently activates Ij, potassium channels in the AV node, thus forcing the membrane potential closer to the Nernst potassium potential thus, adenosine significantly hy-perpolari2Ks this tissue, preventing the conduction of action potentials. The answer is (A). 

Section (4) refers to the restrictions imposed on cation movement by membranes. The relative ease of movement of potassium through a nerve membrane at rest generates a potassium potential. Imposition of a perturbation upon the membrane changes its properties so that it is more permeable to sodium, and the activated membrane shows a sodium potential of reversed sign to the potassium potential. Thereupon a self-propagating spike of depolarization which is rapidly followed by recovery to the rest state fiows along the nerve cell and is the nerve message. 

If the calculated potential equals the actual potential in the cell, then the membrane potential is in fact a potassium potential. There is enough agreement between the calculated and the measured values to conclude that this is probably true. Yet, some have objected that the actual and theoretical values correlate only within narrow limits of potassium concentration. For example, although there is a good correlation at concentration of K equal to 0.5 mM, at concentration of 2.5 mM, the actual intracellular potential, the calculated values are 8 mV higher than the measured potential. 

Equation (22.25) defines the potassium potential If Na+ or Ca + were the permeant ion instead of K+, there would be a different potential. You can think of this potential in two different ways. First, it is the voltage that arises as a counterbalance when an ion flows down its concentration gradient. Second, if... 

EXAMPLE 22.2 A potassium potential in skeletal muscle. In mammalian skeletal muscle, the extracellular potassium concentration is [K lout = 4mM and the intracellular concentration is [K+]in = 155mM. The K+ potential at 37 °C is given by Equation (22.25) ... 

Fig. 2a. Simultaneous recording of membrane PDs (upper) and potassium potentials (lower) by the two barrels of the double-barreled K -selective microelectrode.

Fig. 2. Schematic diagram of recording arrangement. Voltage signals from K and reference rrricro-electrodes amplified with a differential electrometer, negative input from reference electrode records tissue potential changes (V) during neuronal activity. Potassium potential recorded differentially (Ej ) or electronically converted to its antilog approximating aj. ...

Upper traces - changes in potassium potential (tiEy)... 

Thus under standard conditions chloride ions are not oxidised to chlorine by dichromate(Vr) ions. However, it is necessary to emphasise that changes in the concentration of the dichromate(VI) and chloride ions alters their redox potentials as indicated by the Nernst equation. Hence, when concentrated hydrochloric acid is added to solid potassium dichromate and the mixture warmed, chlorine is liberated. 

Acetoxybenzene is prepared by the reaction of benzene with Pd(OAc)2[325,342-345], This reaction is regarded as a potentially useful method for phenol production from benzene, if carried out with only a catalytic amount of Pd(OAc)2. Extensive studies have been carried out on this reaction in order to achieve a high catalytic turnover. In addition to oxygen and Cu(II) salts, other oxidants, such as HNOi, nitrate[346,347], potassium peroxodisulfate[348], and heteropoly acids[349,3S0], are used. HNO is said to... 

The metal-ion complexmg properties of crown ethers are clearly evident m their effects on the solubility and reactivity of ionic compounds m nonpolar media Potassium fluoride (KF) is ionic and practically insoluble m benzene alone but dissolves m it when 18 crown 6 is present This happens because of the electron distribution of 18 crown 6 as shown m Figure 16 2a The electrostatic potential surface consists of essentially two regions an electron rich interior associated with the oxygens and a hydrocarbon like exterior associated with the CH2 groups When KF is added to a solution of 18 crown 6 m benzene potassium ion (K ) interacts with the oxygens of the crown ether to form a Lewis acid Lewis base complex As can be seen m the space filling model of this... 

Other potential sources of potassium include insoluble minerals and ores, and the oceans, which contain 3.9 x 10 t/(km) of seawater (see Ocean RAW materials). The known recoverable potash reserves are sufficient for more than 1000 years at any foreseeable rate of consumption. 

Triduoropyriaiidiae can be prepared ia 85% yield from 2,4,6-trichloropyrioiidiae [3764-01-0] and potassium fluoride ia sulfolane or solvent-free conditions (458,459). Derivatives such as l,l,l-trichloro-3-[5-(2,4,6-trifluoropyrimidyl)]-3,4-epoxybutane [121058-68-2] have been prepared as potential herbicides (460). 

Reference Electrodes and Liquid Junctions. The electrical cincuit of the pH ceU is completed through a salt bridge that usually consists of a concentrated solution of potassium chloride [7447-40-7]. The solution makes contact at one end with the test solution and at the other with a reference electrode of constant potential. The Hquid junction is formed at the area of contact between the salt bridge and the test solution. The mercury—mercurous chloride electrode, the calomel electrode, provides a highly reproducible potential in the potassium chloride bridge solution and is the most widely used reference electrode. However, mercurous chloride is converted readily into mercuric ion and mercury when in contact with concentrated potassium chloride solutions above 80°C. This disproportionation reaction causes an unstable potential with calomel electrodes. Therefore, the silver—silver chloride electrode and the thallium amalgam—thallous chloride electrode often are preferred for measurements above 80°C. However, because silver chloride is relatively soluble in concentrated solutions of potassium chloride, the solution in the electrode chamber must be saturated with silver chloride. 

To prevent radioactive iodides from lodging in the thyroid gland during exposure to excessive radiation, a potential appHcation of iodine acting as a thyroid-blocker has arisen. Eor this purpose potassium iodide was recommended (66). 

Oxidation Reactions. Potassium permanganate is a versatile oxidizing agent characterized by a high standard electrode potential that can be used under a wide range of reaction conditions (100,133—141). The permanganate ion can participate in a reaction in any of three distinct redox couples. 

Sodium and potassium ions are actively absorbed from the intestine. As a consequence of the electrical potential caused by transport of these ions, an equivalent quantity of Cf is absorbed. The resulting osmotic effect causes absorption of water (56). 

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