Question

Explain how botulinum toxin alters the normal sequence of events at the neuromuscular junction to result in paralysis. Be sure to include the vesicular transport process that is inhibited.

Answer 1

Botulinum toxin inhibits muscle contraction by blocking the release of acetylcholine at the neuromuscular junction. It cleaves proteins involved in neurotransmitter release, preventing synaptic vesicles from releasing acetylcholine. This disruption of the normal sequence of events results in paralysis.

Step-by-step explanation:

Botulinum toxin, also known as botox, inhibits muscle contraction by blocking the release of the neurotransmitter acetylcholine (ACh) at the neuromuscular junction. The toxin is composed of a light A subunit and heavy protein chain B subunit. The B subunit binds to neurons to allow botulinum toxin to enter the neurons. Once inside, the A subunit acts as a protease, cleaving proteins that are involved in the release of ACh from the motor neurons.

This cleavage of proteins prevents synaptic vesicles from fusing to the neuron's membrane and releasing ACh. As a result, the normal sequence of events at the neuromuscular junction is disrupted, leading to paralysis. Without the release of ACh, the muscle fibers are not stimulated to contract. This inhibition of muscle contractions causes muscle relaxation.

For example, when botulinum toxin is used for cosmetic purposes, it is injected into specific facial muscles to relax them and reduce the appearance of wrinkles.

Answer 2

At neuromuscular junctions, a neurotransmitter called as acetylcholine if found. Botulinum toxin inhibits the transmission of acetylcholine at the synaptic junctions. Botulin toxin acts at presynaptic junctions and blocks the release of acetylcholine, leading to paralysis.