( This ( ( means ( that ( ( when ( ( the body ) ( ( demands ( more oxygen ) ) ( during exercise ) ) ) ) ( , ( ( less oxygen ) ( reaches ( ( ( ( ( ( ( the brain ) , ) heart ) , ) muscles ) and ) ( other organs ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ means) (SBAR (IN that) (S (SBAR (WHADVP (WRB when)) (S (NP (DT the) (NN body)) (VP (VBZ demands) (NP (JJR more) (NN oxygen)) (PP (IN during) (NP (NN exercise)))))) (, ,) (NP (JJR less) (NN oxygen)) (VP (VBZ reaches) (NP (NP (DT the) (NN brain)) (, ,) (NP (NN heart)) (, ,) (NP (NNS muscles)) (CC and) (NP (JJ other) (NNS organs))))))) (. .)))
This means that when the body demands more oxygen during exercise, less oxygen reaches the brain, heart, muscles and other organs.
(ROOT (S (PP (IN In) (NP (PRP$ your) (NN body))) (, ,) (NP (NP (DT the) (NN heart)) (CC and) (NP (NNS lungs))) (VP (VBP work) (ADVP (RB together)) (S (VP (TO to) (VP (VB make) (ADJP (JJ sure)) (SBAR (IN that) (S (NP (NN oxygen)) (VP (VBZ gets) (PP (TO to) (NP (NP (PDT all) (DT the) (JJ other) (NNS organs)) (PP (IN of) (NP (PRP$ your) (NN body)))))))))))) (. .)))
In your body, the heart and lungs work together to make sure that oxygen gets to all the other organs of your body.