What is the expected consequence of dendrotoxin blocking potassium channels in motor neurons?

• A. Shortened action potential duration.
• B. Enhanced neurotransmitter release.
• C. Prolonged action potential.
• D. Reduced muscle contraction strength.

Answer: (C)

Blocking potassium channels in motor neurons with dendrotoxin primarily leads to a prolonged action potential. During a typical action potential, potassium channels are responsible for repolarizing the membrane potential after the depolarization phase. When the potassium channels are blocked, repolarization is hindered. As a result, the action potential duration increases because the return to the resting membrane potential is delayed.

This alteration in action potential duration can significantly impact neuronal signaling and neurotransmitter release. With a longer action potential, calcium influx may persist for an extended period, potentially leading to enhanced neurotransmitter release following subsequent impulses. However, the most direct and immediate consequence of the potassium channel blockade is the prolongation of the action potential itself, making this the correct consequence of the blockage.

Additional options could involve the muscle contraction strength but are more related to downstream effects rather than the direct result of altered action potential duration due to blocked potassium channels.