Final answer:
Botulinum toxin inhibits acetylcholine release at neuromuscular junctions, resulting in flaccid paralysis but can be used in controlled doses for medical and cosmetic muscle relaxation.
Step-by-step explanation:
The effect of botulinum toxin (Botox) on acetylcholine (Ach) transmission is that it inhibits the release of Ach from axon endings at the neuromuscular junction. Botulinum toxin acts by cleaving proteins necessary for synaptic vesicles to fuse with the membrane of the motor neuron's axon terminal. Without the fusion of these vesicles, Ach release is significantly impaired, preventing muscle contraction and leading to flaccid paralysis, a hallmark of the disease botulism. However, in controlled doses, Botox is used medically and cosmetically to induce muscle relaxation, treating conditions like hyperhidrosis, overactive bladder, eyelid twitching, and reducing the appearance of wrinkles.