What effect would a human disorder that increased the [K+] of the cerebrospinal
ID: 8393 • Letter: W
Question
What effect would a human disorder that increased the [K+] of the cerebrospinal fluid (CSF) from 5mM to 20mM have on action potentials?a. more depolarization would be needed to generate an action potential
b. less depolarization would be needed to generate an action potential
c. it would have no effect on the depolarization needed, but would result in a quicker return to resting potential
d. it would have no effect on the depolarization needed, but would result in a longer return to resting potential
and could you please explain the reason for the answer?
Explanation / Answer
The answer is D. The resting membrane potential is maintained by specific concentration of ions on the intracellular and extracellular side of the membrane. After an action potential, K+ channels open to release K+ions outside the cell. This is necessary to bring back the membrane potential to normal. If the concentration of K+ inside the cell is higher than normal, it will take a longer time for the balance in ions and charge to be achieved on both sides of the membrane. For the resting membrane potential to be achieved, more of these extra K+ ions need to be pushed out of the cell. This would take longer time than usual.
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