( ( Although ( ( the ( muscle ( fiber stimulus ) ) ) ( is all-or-none ) ) ) ( , ( ( entire muscles ) ( ( can ( function ( upon ( graded contractions ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN Although) (S (NP (DT the) (NN muscle) (NN fiber) (NN stimulus)) (VP (VBZ is) (ADJP (JJ all-or-none))))) (, ,) (NP (JJ entire) (NNS muscles)) (VP (MD can) (VP (VB function) (PP (IN upon) (NP (JJ graded) (NNS contractions))))) (. .)))
Although the muscle fiber stimulus is all-or-none, entire muscles can function upon graded contractions.
(ROOT (S (NP (NNS Muscles)) (VP (VBP need) (NP (NN stimulus)) (PP (TO to) (NP (NN contract)))) (. .)))