The reasoning: quantal release, receptor reserve, rapid termination
ACh is synthesised from choline + acetyl‑CoA (choline acetyltransferase), loaded into vesicles (VAChT; ~5,000–10,000 molecules per quantum). A spontaneous single‑vesicle release produces a miniature EPP (~0.5 mV). A nerve AP releases tens to a few hundred quanta (quantal content), producing an EPP well above threshold — a safety factor ≈ 3–5. Adult junctional AChR is α₂βδε (fetal/extrajunctional α₂βγδ). AChE in the basal lamina hydrolyses ACh within ~1 ms; choline is recycled by a high‑affinity transporter (blocked by hemicholinium).