Membrane rest potential

Hodgkin and Huxley [81] formulated a membrane model that accounts for K" ", Na" ", and ion leakage channels in squid giant axons [Fig. 22(a)]. The membrane resting potential for each ion species is treated like a battery and the degree to which the channel is open is modeled by a variable resistor. 

Equations (6.5.1) and (6.5.2) yield the membrane rest potential in the form... 

An examination of the relationship of [K" ]o] and [K+]i] in the Nernst equation shows that an increase in the [K" ]o will result in a decrease in the membrane resting potential (less negative). Changes in the extracellular concentration of another ion (Na+, Ca+", Cl > may also modify the resting potential. 

Figure 19-4 Diagrammatic representation of the membrane action potential, as recorded from a Purkinje fiber, and an electrogram recorded from an isolated ventricular fiber. The membrane resting potential is 90 mV relative to the exterior of the fiber. At the point of depolarization, there is a rapid change (phase 0) to a more positive value. 0-4 indicate the phases of depolarization and repolarization. Note that phases 0 and 3 of the membrane action potential correspond in time to the Inscription of the QRS and T waves. respMively. of the local electrogram.

Cells create potential differences by pumping ions across membranes. The Nemst equation defines the electrical potential arising from differences in ionic concentration created by the various pumps. It relates the membrane resting potential to the charge and concentration of ions on either side of a membrane. 

Is membrane resting potential changed with use of local anesthetics ... 

In humans the main cations acting as electrolytes are Na" ", K, Ca ", and Mg " [10,11]. The main task of Na is to maintain osmolality. By this it is closely correlated with the regulation of the extracellular volume and the water balance. The main functions of K are osmoregulation and maintainance of the membrane resting potential. Ca is a trigger for many enzymes. About 90%... 

It is possible that the stationary-state situations leading to an active ion transport occur only in localized regions of the membrane, i.e., at ATPase molecule units with diameters of about 50 A and a length of 80 A. The vectorial ion currents at locations with a mixed potential and special equipotential lines would appear phenomenologically like ionic channels. If the membrane area where the passive diffusion occurs is large, it may determine the rest potential of the whole cell. 

K Channels belong to a class of membrane proteins that form highly K-selective pores in membranes. All known K Channels are composed of several (usually four) pore forming alpha subunits and auxiliary beta subunits. K Channels play an essential role in cellular excitability, being involved in repolarization of Action Potentials and setting the cell resting potential as well as contributing to potassium homeostasis. 

Resting potential is a stable membrane potential in nonexcitable cells, or the most stable membrane potential between Action Potentials in excitable cells. In some excitable tissues it is impossible to define a resting potential because of continuous change in membrane potential. 

Marine toxins modify the functions of many different types of ion channels in animal cell membranes. These channels may be important for maintaining the cell s resting potential, for generating electrical membrane signals, such as impulses, and for controlling hormonally triggered or metabolic responses. Thus toxins may depolarize membranes, leading to a (sometimes transient) increase in cellular activities, or they may... 

Fromm and Spanswick [79] studied inhibiting effects of DNP on the excitability of willow by recording the resting potential of the phloem cells. In willow, 10 " M DNP rapidly depolarized the membrane potential by about 50 mV. 

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