It is from Crash Course Anatomy & Phisiology. It is at around 1 minute and 30 second to 2 minute. Here it goes:
Because, as unpleasant as a stick in the eye or tack in the foot may be, pain actually is a great example of where everything we have talked about over the last few weeks all come together. As we trace a pain signal through the nervous system, from the first cuss to the Hello Kitty band aid.
Dictionaries say that cuss is the same as curse, but I still cannot understand what it means there.