Nurse Ratched, the antagonist, is drunk with her power until McMurphy arrives and upsets it. Much of her power lies in her ability to emasculate the male patients and maintain a sexless façade. When she is revealed as a woman (McMurphy rips her uniform off, exposing her ample bosom), she loses much of her power.
Although men gain power through sex according to McMurphy’s view of the world, women lose their power through sex. By denying a man sex, a female can symbolically castrate him; by having sex with a woman, a man can weaken her. Power is thus intimately connected with gender in One Flew Over the Cuckoo’s Nest.