Question

What is the key property of axon membranes that accounts for their ability to sustain action potentials? How would each of these scenarios affect action potentials?

1.Voltage-gated Na+ channels are absent

2.Voltage-gated K+ channels are absent

3.Voltage-gated Na+ channels are open for a shorter period of time

4.There is a longer delay before voltage-gated K+ channels open

5.Voltage-gated K+ channels have exactly the same properties as voltage-gated Na+ channels, in terms of latency before opening, open time, and inactivation.

6.Voltage-gated Na+ and voltage-gated K+ channels fail to close once they have opened

7.The Na+/K+ pump is poisoned or ATP is suddenly absent

8.Tetrodotoxin is applied to the neuron

9.NaCl is added to the extracellular fluid

10.KCl is added to the extracellular fluid

Answer 1

1.Voltage-gated Na+ channels are absent

• The Neuron will not be able to trigger an action potential. Due to absent of Na+ channel, the cell will remain at the resting potential of -30 mV and will be prevented from achieving positive membrane potential of +40 mV, so an action potential will not be triggered.

2.Voltage-gated K+ channels are absent

• The neuron cell will lose its ability to repolarize the cell and will not return back to its resting membrane potential.

3.Voltage-gated Na+ channels are open for a shorter period of time

• If Na+ channels are opened for a shorter period of time it will not overcome the threshold potential needed to trigger an action potential.

4.There is a longer delay before voltage-gated K+ channels open

• The neural cell will remain at a depolarized state for a longer period of time. The frequency of conduction of impulse will be slowed down.