after contraction. When inhibitory neurons are unable to release their neurotransmitters, motor neurons fire out of control, and muscles have difficulty relaxing. This causes the muscle spasms and spastic paralysis seen in tetanus infection.

The tetanus toxin, tetanospasmin, is made up of a heavy chain and a light chain. There are three domains, each of which contributes to the toxin's pathophysiology. The heavy chain has two domains. The N-terminal side of the