Scientists have discovered a new planet called Neurvana. Organisms on this plane

Question

Scientists have discovered a new planet called Neurvana. Organisms on this planet use Cs+ and Li+ to regulate membrane potential and neuronal excitability. The physiological concentrations of these ions are as listed below. Additionally, Neurvanians []outside []inside Cs+ 350 mM 15mM Li+ 1 mM 40mM At rest, only Cs+ channels are open.

What is the resting membrane potential of a neuron in this organism?

A change in the membrane potential causes voltage-gated Li+ channels to open. What is the magnitude of the driving force (i.e., potential) that will cause Li+ to move across the membrane, and in which direction will these ions flow? Explain your answer.

At the “peak” of an acton potential, the membrane is 1000x more permeable to Li+ than Cs+. What is the Vm of the cell during this time?

Approximately 1 ms after the initiation of an action potential, these Li+ channels inactivate, and voltage-gated Cs+ channels begin to open. What happens te membrane potential of this cell? Which ions are flowing under these circumstances and in what direction?

Explanation / Answer

Resting membrane potential The following formula is used58 log P [cs ]out + p[li ]out / p [cs]in+ p[li]in The membrane potential is altered by the concentration of ions on both sides of the membrane. p ermeability of cs and Li are 0.17 and 0.08 respectively 58 log x[0.17 x350 +0.08x1 / 0.17x 15 + 0.08x 40] = 58.91 mV = resting membrane potential. Here Li+ concentration is less outside and cs concentration is less inside of the cell and vice versa. As the concentration of the ion changes from its resting concentration action potential is trigggered. Li+ ion flow flow outward to the cell and cs+ ion moves inside the cell. Because of this movement the membrane becomes more and more positive causing depolarisation . At the peak of the action potential , the membrane becomes more positive compared to the resting membrane potential . After 1ms of initiation of action potential , cs ion gates close and li+ ion channels open allowing li+ ions flow from inside to outide of the cell. Cs+ flows from outside to inside . As cs+ gates are closed it cannot flow into the cell.

Related Questions

Navigate

• Browse (All)
• Browse S
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.