Sentence:  Since electrical stimulation of the posterior hypothalamus produces the effects of wakefulness while stimulation of the anterior hypothalamus induces sleep , it may be said that the reactivity of the whole <WSD>organism</WSD> is altered by a change in the autonomic reactivity of the hypothalamus . 
Meaning of the word marked with <WSD> tags:  a living thing that has (or can develop) the ability to act or function independently