Question

Plot the voltage of the cell using the original parameters for
Na, K and Cl, and changing sodium permeability from 1 to 10, 100,
1000 and up to 9999. Will the voltage keep increasing positively as
the permeability to sodium is increasing? Why?

Plot the voltage of the cell using the original parameters for
Na, K and Cl, and changing potassium permeability from 1 to 10,
100, 1000 and up to 9999. Will the voltage keep increasing
negatively as the permeability to potassium is increasing?
Why?

In the Goldman equation, Ki and Nai are on the top of the
equation ratio, but Cli is on the bottom. Why?

Summary:

State the important principles that you have discovered in
working with the Goldman equation using the Nernst/Goldman
simulator.

Answer #1

1ans.**increase** the **permeability**
of an axonal **membrane** to **sodium**
ions, the equilibrium **potential** for
**sodium** in the cell .**increase**,
because the influx of **sodium** depolarizes the
neuron.balance the inward directed chemical gradient for Na+, the
cell interior needs to be +52 mV to prevent Na+ from diffusing into
the cell. ... Therefore, while the resting
**potential** is far removed from the ENa, the peak of
the action **potential** approaches ENa.

2ans.increase the **membrane potential**
(hyperpolarize the cell) because the presence of extra
**potassium** outside the cell will make the
**potassium equilibrium potential** more
**negative**. c. increase the **membrane
potential** because the excess positive charge on the
outside of the cell makes the inside relatively more
**negative**.

4) Recall that after the Na+ channels open the K+ channels open.
Again to make the calculations relatively simple, solve the Goldman
equation again with all resting conditions EXCEPT a 100 fold
increase in potassium permeability. (2 points) [Hints, first, while
I always stress the importance of units, in this case the
simplified equation uses lumped constants (RT/F) and thus the units
are factored in – so you can, this time, ignore the units. Second,
remember that Cl- is a...

5) A new drug has been discovered that completely opens the
voltage-gated potassium channels. If this drug is used
experimentally on an isolated axon, the membrane potential can be
easily measured. Assume that this experiment provided the following
results. The extracellular Na+ is 145 mM and the extracellular K+
is 4mM, the measured membrane potential in the presence of the drug
is -94mV. Using this information, calculate the intracellular K+
concentration.
To solve this equation, you will need to use...

1) Answer the following questions:
a) Explain a concentration gradient using K+,
Na+, and Cl-.
b) I have a nerve cell and sodium channels are blocked. What
happens when potassium rushed out of the cell?

As a result of an experiment following measurements were
obtained from a cell:
intracellular Na+ concentration of 20
mM,
intracellular K+ concentration of 100
mM,
intracellular Cl- concentration of 60
mM,
intracellular Ca2+ concentration of 0.0001
mM,
extracellular Na+ concentration of 150
mM,
extracellular K+ concentration of 5
mM,
extracellular Cl- concentration of 120
mM,
extracellular Ca2+ concentration of 2
mM.
Using these values calculate equilibrium potential for
K+ ion in these cells. (RT/F = 26.7 mV, 37oC;
Use original...

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