In what clic Star Trek episode does Nurse Chapel slap Mr. Spock back to consciousness?

He's in sick bay in some Vulcan-type trance. He starts to come to and calls Nurse Chapel. He tells her to hit him, hit him harder. Mindful of her unspoken love for him she is hesitant but does it. Eventually Dr. McCoy rushes in to stop her but Mr. Spock, now fully aware, explains that he asked her to do it. Please name the title of the episode and maybe which season it comes from.