 For instance, Sema3a repels axons from the dorsal root ganglia, facial nerves, vagal nerves, olfactory-sensory, cortical nerves, hippocampal nerves and cerebellar nerves.Class 3 semaphorins have an important function after traumatic central nervous system injuries, such as spinal cord injury.They regulate neuronal and non-neuronal cells associated with the traumatic injury due to their presence in the scar tissue.