( It ( ( is ( ( the function ) ( of ( the ( nervous ( system ( to ( maintain ( this homeostasis ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (NP (NP (DT the) (NN function)) (PP (IN of) (NP (DT the) (JJ nervous) (NN system) (S (VP (TO to) (VP (VB maintain) (NP (DT this) (NNS homeostasis))))))))) (. .)))
It is the function of the nervous system to maintain this homeostasis.
(ROOT (S (NP (DT The) (JJ nervous) (NN system)) (VP (VBZ plays) (NP (NP (DT a) (JJ critical) (NN role)) (PP (IN in) (NP (NP (DT the) (NN regulation)) (PP (IN of) (NP (NN vascular) (NNS homeostasis))))))) (. .)))