Acetylcholine is a neurotransmitter that binds to receptors on skeletal muscle cells. The receptor-signal complex brings about a series of events that result in contraction of skeletal muscle. Venom from black widow spiders causes an explosive release of acetylcholine. What would that do to its victims?

paralysis, lack of breath and death (because of a great deal of Acetylcholine)

Explanation:

The receptor-signal complex brings about a series of events that result in contraction of skeletal muscle. So, if a black widow spider bites you, its venom will cause your muscular system to paralyze, as well as your lack of breathing and lack of heartbeat leading you to die.