Synapsin is like a tiny messenger in our brains that helps our brain cells (neurons) communicate with each other. Think of it like a bunch of toy cars on a track. When the cars are all lined up, they can't move around or do anything fun. But when someone comes along and moves the first car, it sets off a chain reaction and all the cars start moving too. Synapsin is kind of like the toy car that starts the chain reaction.
When our brains think or feel something, electrical signals travel through our neurons like little bolts of lightning. These signals can't jump from one neuron to the next by themselves, so they need some help. That's where synapsin comes in. It helps the electrical signal jump from one neuron to the next by releasing a special kind of chemical called a neurotransmitter. This neurotransmitter is like a little package of information that travels across the gap (or "synapse") between the neurons, carrying the electrical signal with it.
So when you feel happy or sad or excited or scared, it's because different parts of your brain are talking to each other through these electrical signals and neurotransmitters, all thanks to synapsin. It's a really important and helpful part of how our brains work!