Tetanus affects primarily

The manifestation of tetanus is due to tetanospasmin. The tetanus toxin specifically blocks synaptic inhibition in the spinal cord, presumably at inhibitory terminals that use glycine and GABA. The toxin acts presynaptically. The abolition of spinal inhibition causes the uncontrolled spread of impulses initiated anywhere in the central nervous system. This results in muscle rigidity and spasms due to the simultaneous contraction of agonist and antagonists in the absence of reciprocal inhibition. Reference: Textbook of Microbiology; Anathanarayan and paniker's; 10th edition; Page no: 265