Thus, chemical messages are not rapidly terminated as they should be, and normal transmission of impulses across the synapse is disrupted. If the disruption sufficiently prolonged, the system the post-synaptic for relaying impulses across membrane and beyond will be run down, leading to synaptic block, i.e. no synaptic transmission at all. Synaptic blockage causes tetanus (rigid fixation of muscle) and in vertebrates death is likely to follow quickly as a result of consequent paralysis of the diaphragm muscles and respiratory failure. Anticholinesterases act upon cholinergic junctions throughout the vertebrate nervous system, both central and peripheral, the pattern depending on the compound in question and the species affected Typical symptoms include tremors, convulsions respiratory and circulatory failure, coma, dizziness and depression.