BIOPHYSICS N°13 (FILL)

For most living cells, the only ions that can exert any significant influence on

bioelectrical phenomena are ...............

Big three ion K-Na-Cl

............... equation represents the more physiologically realistic case in which the

membrane shows a finite permeability to three different ions.

Goldmann

Lesions in one or more subunits of the KIR channels are linked

to ............. of infancy

Persist hyperinsulinemia hypoglycemia

At rest, membrane permeability of most cells, including

neurons, is greatest for ..............

K+

Because in absolute terms the extracellular potassium concentration is

comparatively ............. . Increases in [K+]e of only a few mM can have enormous effects on

resting membrane potential.

Small

Changes in [K+]e can occur as a consequence of ............. that rapidly

release large absolute amounts of K+ into the blood stream.

Crushing injuries

Alteration in membrane permeability to ions can arise as a

consequence of an extraordinary number of pathological defects in ion channel proteins or

................

Channolopothies

Mutations in KIR channels have been linked to persistent

hyperinsulinemic hypoglycemia of ............

Pancreatic cells

When an ion is in equilibrium across a membrane i.e. μ i= μe,

then ∆μ= ................

0

Resting membrane potential can be measured experimentally or estimated using

................ equation.

Goldmann equation

The combination of 1) .............. and 2)

differential permeability to selected ions is the basis for the generation of transmembrane

potential differences.

Na-K Gradient

Cell membranes show different degrees of permeability to different ions, owing to

the inherent selectivity of specific .........

Ion channel

The numerical value of the membrane potential is generally

negative, meaning that the inside of the cell is ............... with respect to the outside

solution, which is taken as the reference or ............... value.

Negative, standard

The electrochemical driving force equation is .........

where .........

F= Em-Ei where F=FORCE, Em = Membrane potential, Ei = Equilibrium potential

................ equation illustrates the resting membrane potential dependence of some

cells on the interplay between gK and gNa. It can be used to calculate the approximate

value of the resting membrane potential.

Goldmann hodg katz

Conductance is defined by the formula: .............. where ...............

g = 1/R where R=RESISTENCE

Factors contributing to the resting membrane potential are:

1).............

2)............

3)............

1. Gibbs Donnan equilibrium

2. Electrogenic Na-K ATPase

3. electro diffusion of ions

In the disease .............. the observed hyperexcitability of skeletal

muscle cells results from a decreased PCl.

Myotonia congenita

The interior of animal cells is electrically ............... with respect to the external

solution.

Negative

The only ions that can exert any significant influence on bioelectrical phenomena

are .............

Na+, K+, Cl-

The voltage across the cell membrane is the difference between ............... and ...............

Potential inside the cell, potential outside the cell

The formula that relates ion current and ion flux is ................:

Where ...........

GOLDMAN-HODGIN-KATS FIELD

equation, where: P = Permeability

The membrane conductance is the reciprocal of ..........

Membrane resistance

If the electric field across a membrane is constant, then we can write that dφ /

dx = ..........

E = 0

The Nernst-PIanck molar flux equation in terms of dimensionless potential and can be

written as ............

J = -uRT dC/dx - cuzF dɸ/dx

The Goldman equation is valid only when the net current flow

across the membrane is ...........

Constant

The resting membrane potential is mainly determined by the

............. gradient.

K+

For a typical animal cell, the resting membrane potential is

determined by the equilibrium distribution of K+ ions across the cell membrane. The

movement of K+ across the membrane occurs through .............. channels.

Selective ions

Resting membrane potential depends on the product of the ion concentrations and

.............

Temperature

If a membrane is impermeable to Na+ and Cl-, the Goldman equation reduces to

............... for K+.

Nernst equation