( ( When ( ( blood vessels ) constrict ) ) ( , ( ( ( the flow ) ( of blood ) ) ( ( is ( ( ( ( restricted or ) decreased ) , ) ( thus ( ( ( retaining ( body heat ) ) or ) ( increasing ( vascular resistance ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NN blood) (NNS vessels)) (VP (VBP constrict)))) (, ,) (NP (NP (DT the) (NN flow)) (PP (IN of) (NP (NN blood)))) (VP (VBZ is) (VP (VBN restricted) (CC or) (VBN decreased) (, ,) (S (ADVP (RB thus)) (VP (VP (VBG retaining) (NP (NN body) (NN heat))) (CC or) (VP (VBG increasing) (NP (NN vascular) (NN resistance))))))) (. .)))
When blood vessels constrict, the flow of blood is restricted or decreased, thus retaining body heat or increasing vascular resistance.
(ROOT (S (NP (NNP Blood)) (VP (VBP flow) (VP (VB decrease) (SBAR (WHADVP (WRB when)) (S (NP (NN blood) (NNS vessels)) (VP (VBP constrict)))))) (. .)))