Video Transcript
When the resting potential is being maintained, are the potassium ion channels, leak
channels, open or closed? (A) Closed, (B) open.
The following question asks us about a characteristic of nerve cells called the
resting potential. To answer this question, let’s review what the resting potential is and how the
potassium ion channels contribute to its maintenance. When a neuron is not transmitting a signal, it is said to be at rest. The resting potential is the membrane potential when the neuron is at rest. The membrane potential is the difference in ion charge between the inside and outside
of the neuron. When a neuron is at rest, the membrane potential is negative, which means the
cytoplasm is more negatively charged than the extracellular space.
To maintain the cytoplasm as more negative, the sodium–potassium pump and the
potassium ion channels move ions between the extracellular space and the
cytoplasm. The sodium–potassium pump will move three sodium ions into the extracellular space
while importing two potassium ions into the cytoplasm of the neuron. The action of the sodium–potassium pump requires energy in the form of ATP to pump
the ions against their concentration gradient from areas of low to high
concentration. This movement of sodium and potassium ions creates a net negative charge inside the
neuron.
In addition to the action of the sodium–potassium pump, the potassium ion channels,
or leak channels, allow potassium to passively leave the neuron because they are
always open. This allows potassium ions to move down their concentration gradient, causing the
cytoplasm to become more negative, further lowering the membrane potential. So, the action of the sodium–potassium pump along with the potassium ion channels,
which are always open, maintain the resting potential.
Now that we have reviewed how the resting potential is maintained by the
sodium–potassium pumps and the potassium ion channels, we’re ready to answer the
question. When the resting potential is being maintained, the potassium ion channels are
open.
