Question

how does diabetes affect the nervous systems and immune system

Answer 1

well .. glucose is fuel for the body .. for the brain .. for the cells .. when the glucose is not stable .. either when its very increased .. or decrease ( insulin injection is administrated )
of course some really bad symptoms will happen .. for example
when its severely increase it may cause symptoms like seizure ,coma , or even death
in contrast .. when its severely decrease it will cause sweating, palpitations, anxiety, nausea and tremor