You are recording a neuron, and the cell is at resting membrane potential (-70mV

Question

You are recording a neuron, and the cell is at resting membrane potential (-70mV) when you inject a small amount of current eliciting a 5 mV increase that fades. You inject double the amount of current and elicit a 10 mV increase that fades. You inject 3 times the original amount of current, and now you see an action potential as such:

First, what is the approximate threshold of this neuron?

If you inject a current that is four times your original, what do you expect to see happen to the action potential?

What happens to the action potential when you apply the following drugs individually to the recording chamber

A. tetrodotoxin (blocks voltage gated Na+ channels)

B. TEA (blocks voltage gated K+ channels)

Explanation / Answer

Treshold potential is the critical level to which a membrane potential must be depolarised to initiate action potential.so in the given graph,the action potential is produced at three times the stimulus(3*5mv= 15mv).

Treshold potential is - 70+15=. -55mv

if the current is increased more than treshold,it is called supratreshold potential and it increases the frequency of action potential.

Tetrodotoxin inhibits firing of action potential and blocks excitability

TEA increases the duration of action potential

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