nerve
Explanation
The comic features a conversation between two characters about the enteric nervous system -- the network of neurons embedded in the lining of the gastrointestinal tract, sometimes called the "second brain." One character says they'll get their nerve checked, and the other clarifies they're not talking about the brain but the enteric nerve system. When asked to elaborate, they explain that the "second brain" governing gut functions "has 100 million neurons, that's about the same as a dog's brain," and suggests "we should give it some space."
The punchline comes when the character decides to "reach out" to their gut brain and ask it about its interests -- to which the gut responds that it's interested in "liquor and cake." The final panel shows a character saying "back off" -- the gut brain asserting its independence.
The humor plays on the real science of the enteric nervous system, which genuinely contains roughly 100 million neurons and operates semi-independently from the central nervous system. The comic anthropomorphizes this "second brain" and imagines what would happen if we tried to communicate with it as though it were a separate conscious entity. The gut brain's stated interests in liquor and cake are funny because they represent the base cravings and impulses that our "higher" brain often tries to override -- the joke suggests that our gut instincts are literally just a simpler creature inside us that wants junk food and alcohol. The "back off" at the end personifies the gut as a surly, independent entity that doesn't want to be managed by the "main" brain.