What makes a joke funny? The frontal lobe acts as a gatekeeper that sort of determines whether we as individuals get the joke, and if we do, it sends a signal throughout the brain that lights up certain areas of the brain, which releases serotonin into the brain which makes you happy. Serotonin is the chemical that is responsible for your happiness, but it's also to blame if you're in a bad mood. It acts as a regulator that sort of determines how you're going to feel at any given time, also 80% of the serotonin in your body can be found in your gut, which is you're hangry (hungry and angry) all the time. 

Short-term benefits
 

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A good laugh has great short-term effects. When you start to laugh, it doesn't just lighten your load mentally, it actually induces physical changes in your body.

Long-term effects
Laughter isn't just a quick pick-me-up, though. It's also good for you over the long term. Laughter may:
Increase personal satisfaction. Laughter can also make it easier to cope with difficult situations. It also helps you connect with other people.
Improve your mood. Many people experience depression, sometimes due to chronic illnesses. Laughter can help lessen your depression and anxiety and may make you feel happier.
 

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