Which of the following is the key event at a membrane potential of –26 mV? a. Th

Question

Which of the following is the key event at a membrane potential of –26 mV?

a. The late outward current increases in magnitude

b. The late outward current decreases in magnitude

c. The early current reverses its polarity

d. The early and late currents flow inward

Which of the following is the key event at a membrane potential of 26 mV?

a. The late outward current increases in magnitude

b. The late outward current decreases in magnitude

c. The early current reverses its polarity

d. The early and late currents flow inward

e. The early current is at its maximum

Explanation / Answer

1)c. The early current reverses it's polarity.

The resting membrane potential of -70 increase to -26 due to the opening of sodium ion channels allowing the inward flow of sodium ions (positive charge) reversing the polarity across the membrane. In other words depolarizing it.

Outward currents include include that of chlorine and potassium. The former alone cannot achieve depolarization while the latter would end up polarizing the membrane. There is no late inward current.

2)e. The early current is at its maximum.

Maximum number of sodium channels are open now and hence heavy accumulation of sodium occur at the intracellular side of the membrane further increasing the potential from -26 to 26

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