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 smae as curse, but still cannot understand what it means there.