Assignment

 1.  Set the Stim1 with a current of 10 nA current for a duration of 2 ms and Stim2 with a current of 10 nA for a duration of 30 ms duration. What are the differences do you observe in the firing of action potential when Stim1 and Stim2 inputs are given?

2.   What happens to the amplitude of the spike if you increase the current of Stim1 from 10 to 30 nA? Run the simulator by clicking Stim1 button. Note the difference.

3.   If the duration of Stim2 is changed from 2 to 10 ms, what change you are likely to observe? Is there any change in the number of spikes? If so, how many number of spikes did you observe?

4.  Repeat the problem 1 by changing the current of Stim 1 to 50 nA for a duration of 2 ms and the current of Stim 2 to 10 nA for the same duration. What are the differences do you likely observe?

Additional questions you would like to try:

1.   Why are action potential propagated in only one direction along an axon? What occurs when this propagation is interrupted?

2.   Test the generation of action potential with different stimulus inputs and also check it by varying the length of these stimulus inputs using the online neuron simulator.

3.   Test the hypothesis that the frequency (i.e., number per unit time) of action potentials is determined by the stimulus amplitude. Draw a graph of the frequency of action potentials vs. the amplitude of the stimulus.

Hint: To do this, you will have to prolong the duration of the stimulus to 100 ms and use a long(say 90 ms) current pulse stimuli. 

4.    Test the hypothesis that prior depolarization inactivates voltage-gated sodium channels.

Hint: Looking at the behavior of the sodium channels is much easier if you set the potassium conductance to zero.

 5.   Test the hypothesis that the potassium channels DO NOT inactivate following prior depolarization.