Tetanospasmin is the toxin responsible for the clinical manifestations of tetanus.
Once the toxin enters an open wound, the spores germinate and grow if the wound is deprived of oxygen.
Stepping on a nail causes the bacterium to be pushed so deep into the tissues and it usually becomes deprived of oxygen
Only about 12% of tetanus infections in the U.S. from 1998-2000 were the result of a person stepping on a nail. Endospores can enter the body through even the smallest break in the skin.
There have been cases with patients reporting no injury before developing tetanus.
Due to bacterium entering the wound weeks to even years prior and the wound healed.
Since the wound had high oxygen content, the endospores did not germinate, but once the wound was deprived of oxygen, the tetanospasmin toxin was released and caused tetanus.
Tetanospasmin is a neurotoxin meaning it acts on the nervous system
The bacterium remains in the wound, and the toxin will travel to the nerves
Once the toxin is in the motor neuron, it is transported to the spinal cord and enters an inhibitory neuron.
Inhibitory neurons prevent muscle contractions, but the toxin will prevent the release of the neurotransmitters causing no inhibition of muscle contractions.
Ultimately this causes severe and violent contractions of all the major muscle groups