estion 3, You are studying the electrical properties of a neuron in a dish. The

Question

estion 3, You are studying the electrical properties of a neuron in a dish. The extracelular lution bathing the cell contains 145 mM Nat and 5.6 mM Kt, You determine that under these itions, the Nat equilibrium potential is +35 mV and the K+ equilibrium potential is 60 mV All measurements are conducted at room temperature. a. (2 pts) What are the intracelular Nat and K+ concentrations? (2 pts) If you held the neuron at +20 mV, in which direction would the net flow of each ion be? b. (2 pts) If you held the neuron at +50 mV, in which direction would the net flow of each ion be? e.

Explanation / Answer

Ans. As per the membrane potential equation we would have the intracellular concentration of Na+ ions as

35 = 2.303 x 8.314 x 298/ 96485 log 145 / x

Hence intracellular concentration of Na+ ions would be 37.103 mM

The intracellular concentration of K+ ions would be

-60 = 2.303 x 8.314 x 298/96485 log 5.6/x

Hence intracellular concentration would be 57.93 mM

Ans 3 b If the neurons are held at +20mV the sodium ions tend to diffuse out and potassium ions would diffuse in throught the Na+-K+ potassium channels, which pumps 3 sodium ions for 2 potassium ions.

Ans 3c, The same above case would be considered if the neuron is held at +50 mV. Sodium ions tend to diffuse if the negative potential is observed.

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