Final answer:
McMurphy reacts to the ward's atmosphere with challenge and resistance, seeking to inspire change and assert individuality among the patients against the oppressive environment.
Step-by-step explanation:
Upon encountering the atmosphere of the ward, the character McMurphy from Ken Kesey's novel One Flew Over the Cuckoo's Nest shows a reaction of challenge and resistance. McMurphy's lively and rebellious spirit immediately sets him at odds with the oppressive and demoralizing environment that he finds there.
His reaction is to provoke change and incite the other patients to assert their individuality against the authoritarian rule of Nurse Ratched, personifying a battle for human dignity and freedom within the clinical, controlling confines of the mental institution.