Neurotransmitters are chemical messengers that coordinate the transmission of signals from one nerve cell (neuron) to the next.eurotransmitters are chemical messengers that coordinate the transmission of signals from one nerve cell (neuron) to the next.
Soldiers in the secondary zone may be boarded with 16 months time-in-service and four months time-in-grade as of the first day of the board month. The time-in-service requirement for attaining eligibility for promotion to SSG is 84 months Active Federal Service for the primary zone and 48 months for the secondary zone.
The promotion criteria for promotion to the ranks of E-2 to E-4 are: 1  Private (E-2) - Six months time-in-grade (TIG) as a private (E-1). 2  Private First Class (E-3) - Four months TIG as a Private (E-2) and 12 months time-in-service (TIS).  Specialist/Corporal (E-4) - 6 months TIG with 24 months TIS.