Question

the bacterium clostridium botulium secrete botilium toxin, the toxin blocks the release of acetycholine from the axon terminal of a motor neuron. explain how the toxin binding would change the normal sequence of event at the neuromuscular junction.

Answer 1

The normal sequence of events at a neuromuscular junction are:  

1. An action potential reaches the presynaptic axon terminal of a motor neuron.
2. Opening of voltage gated calcium channels and influx of calcium from synaptic cleft into presynaptic neuron.
3. Movement of neurotransmitter vesicles filled with acetylcholine to move towards axon terminal membrane.
4. Release of acetylcholine.
5. Binding of acetylcholine with receptors on post synaptic membrane.
6. Opening of ion channels in presynaptic membrane.
7. Influx of Na+ and Ca++
8. Muscle contraction.

what happens when botulium toxin binds?

It blocks the release of acetylcholine from presynaptic neuron and thus the normal events at neuromuscular junction cannot take place.This will inhibit muscle contraction and lead to muscle weaknesses or paralysis and atrophy.