Scott: Doctor, I've seen the captain feverish, sick, drunk, delirious, terrified, overjoyed, boiling mad... But up to now, I have never seen him red-faced with hysteria.
Kang: Kirk, my ship is disabled. I claim yours. You are now prisoners of the Klingon empire against which you have committed a wanton act of war!
Answer: Kirk was getting his physical and Dr. McCoy probably turned off communications, because if he hadn't, Kirk would have left and headed straight for the bridge, leaving McCoy irritated.