Question 4. You record the electrical activity of a neuron with intracellular el
ID: 193438 • Letter: Q
Question
Question 4. You record the electrical activity of a neuron with intracellular electrodes. The normal resting membrane potential is measured to be-50 mV. When Na channels are blocked the resting potential is -64 mV. When K' channels are blocked, the resting potential is +29 mV. Assume that the membrane is not permeable to any other ions. All measurements are conducted at room temperature. a. (2 pts) What are the equilibrium potentials for Na" and K? b. (2 pts) What ratio of K' to Na" permeability would account for the neuron's normal resting potential? c. (2 pts) If you suddenly made the cell much more permeable to K', what would happen to 0 neuron's resting potential? Near what value would it stabilize? d. (2 pts) If you were to add KCI to the extracellular solution so that the external K concentration became equal to the intracellular K concentration, what would the cell's resting potential become? (Hint: first determine the new Ex)Explanation / Answer
a) Equilibrium potentials of K+ and Na+ are around -90 mV and +60 mV respectively.
b) The ratio of Two K+ ions inside the cell and three Na+ ions outside the cell would account for the neuron's normal resting potential.
c) If you suddenly make the cell more permeable to K+,more K+ will come inside the cell to make it more negative.It would be stabilized near -90 mV value.
d) If you add KCl to extracellular solution,K+ will move down the concentration gradient to the inside cell.So Cl- will be higher outside and K+ will be higher inside so as to give rise to net positive resting potential.The resting potential can be calculated by Nernst equation that is-
Ek=RT/ZFln[KR]/[KL]
Where R=gas constant,T=absolute temperature in Kelvin,Z=the charge/valency,F=Faraday constant,
[KR] and [KL] are the K+ concentrations inside and outside of the cell,respectively.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.