AAMI Microbiology for Embalmers Practice Exam

Tetanus, producing the telltale lockjaw, is caused by a toxin from Clostridium tetani, an anaerobic bacillus that forms spores. The toxin, tetanospasmin, travels to the central nervous system and blocks the release of inhibitory neurotransmitters like GABA and glycine. Without those inhibitory signals, motor neurons fire unchecked, leading to rigid, prolonged muscle contractions—especially in the jaw muscles—giving the characteristic locking of the jaw. This explanation fits because the paralysis and spasms come from an exotoxin produced by a bacterium, not from a protozoan parasite, a virus, or a fungus.