Bioelectric Phenomena - Introduction to Biomedical Engineering - page 809

Na þ , K þ , and Cl are the only

5. Derive the Goldman equation for a membrane in which

permeable ions.
6. Calculate V m for the frog skeletal muscle at room temperature.

7. The following steady-state concentrations and permeabilities are given for a red blood cell
membrane.
Ion Cytoplasm (mM) Extracellular Fluid (mM) Ratio of Permeabilities
K þ 140 4 1.0
Na þ 11 145 0.54
Cl 80 116 0.21
(a) Find the Nernst potential for each ion. (b) What is the resting potential predicted by the
Goldman equation?
8. The following steady-state concentrations and permeabilities are given for a skeletal muscle
membrane.
Ion Cytoplasm (mM) Extracellular Fluid (mM) Ratio of Permeabilities
K þ 150 5 0.1
Na þ 12 145 0.001
Cl 4 116 1.0
(a) Find the Nernst potential for each ion. (b) What is the resting potential predicted by the
Goldman equation?
9. The following steady-state concentrations and permeabilities are given for a membrane.
Ion

Cytoplasm (mM) Extracellular Fluid (mM) Ratio of Permeabilities

K þ 140 2.5 1.0

Na þ

13 110 0.019

Cl 3 90 0.381

K þ . (b) What is the resting potential predicted by the
Goldman equation? (c) Explain whether space charge neutrality is satisfied. (d) Explain why
the steady-state membrane potential does not equal zero.
10. A membrane has the following concentrations and permeabilities.
Ion

(a) Find the Nernst potential for

Cytoplasm (mM) Extracellular Fluid (mM) Ratio of Permeabilities

K þ ? 4 ?

Na þ 41 276 0.017

Cl

52 340 0.412

K þ

The resting potential of the membrane is 52 mV at room temperature. Find the

cytoplasm concentration.
11. The following steady-state concentrations and permeabilities are given for a membrane. Note
that A þ is not permeable.

Ion Cytoplasm (mM) Extracellular Fluid (mM) Ratio of Permeabilities

K þ

136 15 1.0

Na þ

19 155 0.019

Cl

78 112 0.381

A þ 64 12 —

Continued