Question

This question is about the potassium ion: 1) what does potassium do at the passive potassium channels of neurons, 2) what is the role for potassium in the voltage-gated potassium channels, and 3) what is the role of potassium in chemically-gated channels that open a channel for potassium? Also, for 1), 2), and 3), where are each of these located on the neuron?

Answer 1

In al those types of channels potassium plays the role of being the ion being transported across across such channels, but the difference lies in the signal that triggers the transport.

1) This channels will let through potassium ions without spending any energy (ATP), but the transport will always follow the electrical and concentration gradients. Potassium in this case has a role in making resting potential. These channels are located mainly in the dendrites, but there are some in the cell body and the axon.

2) This channel will let through potassium ions without spending energy (ATP), but the channels will only open in response to voltage changes in the cell membrane, when open they will allow potassium ions out of the cell. In this case potassium plays a major role in action potential generation. These are located along the axons.

3) This channels will open in response to chemical signals, like neurotransmiters (acetylcholine), to let through potassium ions. In this case the potassium is producing a synaptic potential. These channels are thus located in the synaptic cleft, in the postsynaptic membrane.