( ( Since ( ( the brain ) ( is ( ( the ( ( most complex ) organ ) ) ( in ( the ( human body ) ) ) ) ) ) ) ( , ( it ( ( ( ( is not ) surprising ) ( that ( things ( can ( ( go wrong ) ( with it ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN Since) (S (NP (DT the) (NN brain)) (VP (VBZ is) (NP (NP (DT the) (ADJP (RBS most) (JJ complex)) (NN organ)) (PP (IN in) (NP (DT the) (JJ human) (NN body))))))) (, ,) (NP (PRP it)) (VP (VBZ is) (RB not) (ADJP (JJ surprising)) (SBAR (IN that) (S (NP (NNS things)) (VP (MD can) (VP (VB go) (ADJP (JJ wrong)) (PP (IN with) (NP (PRP it)))))))) (. .)))
Since the brain is the most complex organ in the human body, it is not surprising that things can go wrong with it.
(ROOT (S (NP (DT The) (NN brain)) (VP (VBZ is) (NP (NP (DT the) (ADJP (RBS most) (JJ complex)) (NN organ)) (PP (IN in) (NP (DT the) (JJ human) (NN body))))) (. .)))