Tetanus is caused by an a-b exotoxin called , which is produced by clostridium tetani.

Collagenase is produced by several species of Clostridium, facilitates the spread of gas gangrene. And toxins are produced and secreted by actively growing cells, may be found in foods but are usually inactivated by cooking, the host typically responds by producing antibodies called antitoxin, may be toxic in very tiny amounts, may be produced by gram negative or gram positive bacteria; examples include tetanus toxin, cholera toxin, and staphyloccal enterotoxin.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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