▁a ▁type ▁of ▁tunnel ▁that ▁leads ▁toward ▁the ▁target ▁neur ons . ▁This ▁tunnel ▁is ▁known ▁as ▁band ▁of ▁Bü ng ner , ▁a ▁guidance ▁track ▁for ▁the ▁reg ener ating ▁ax ons , ▁which ▁behav es ▁like ▁an ▁end one ural ▁t ube . ▁The ▁st ump ▁of ▁the ▁dam aged ▁ax on ▁is ▁able ▁to ▁spr out , ▁and ▁those ▁spr outs ▁that ▁grow ▁through ▁the ▁Schw ann - cell ▁“ t unnel ” ▁do ▁so ▁at ▁the ▁rate ▁around ▁ 1 ▁mm / day ▁in ▁good ▁conditions . ▁The ▁rate ▁of ▁reg ener ation ▁decre ases ▁with ▁time . ▁Success ful ▁ax ons ▁can , ▁therefore , ▁re connect ▁with ▁the ▁mus cles ▁or ▁org ans ▁they ▁previously ▁controlled ▁with ▁the ▁help ▁of ▁Schw ann ▁cells , ▁but ▁specific ity ▁is ▁not ▁maintained ▁and ▁errors ▁are ▁frequent , ▁especially ▁when ▁long ▁distances ▁are ▁involved . ▁Because ▁of ▁their ▁ability ▁to ▁impact ▁reg ener ation ▁of ▁ax ons , ▁Schw ann ▁cells ▁have ▁been ▁connected ▁to ▁prefer ential ▁motor ▁re inner v ation , ▁as ▁well . ▁ ▁If ▁Schw ann ▁cells ▁are ▁prevent ed ▁from ▁associ ating ▁with ▁ax ons , ▁the ▁ax ons ▁die . ▁Reg ener ating ▁ax ons ▁will ▁not ▁reach ▁any ▁target ▁unless ▁Schw ann ▁cells ▁are ▁there ▁to ▁support ▁them ▁and ▁guide ▁them . ▁They ▁have ▁been ▁shown ▁to ▁be ▁in ▁advance ▁of ▁the ▁growth ▁con es . ▁▁ ▁Schw ann ▁cells ▁are ▁essential ▁for ▁the ▁maintenance ▁of ▁health y ▁ax ons . ▁They ▁produce