I\'m trying to understand if an action potential will happen in this scenario fo

Question

I'm trying to understand if an action potential will happen in this scenario for a lab report I'm writing:

Tetraethylammonium (blocks voltage gated potassium channels) was administered on a frog gastrocnemius. From my understanding, this drug would block the voltage gated potassium channels in the neuron(s) from functioning therefore depolarization of the action potential should occur as normal. However, repolarization (+hyperpoliarization) would not occur. My question is, if the action potential is allowed to depolarize but not reploarize, what happens in the neuromusclular junction? Does the constant depolarization result in continuous exocytosis of the excitatory neurotransmitters (leading to constant muscle contraction)? Or does the action potential not occur at all and therefore, no muscle contraction occurs?

Explanation / Answer

Tetraethyl ammonium blocks voltage gated potassium channels. Since potassium channels are involved in repolarisation and hyperpolarisation phases of action potential, tetraethyl ammonium causes prolongation of action potential. It increases the contractile force of muscle contraction. Action potential will occur because the concentration gradient of sodium and potassium is the activity of Na/K pump and not the potassium channels.

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