Neurons are the cells that transmit information between your brain and different parts of your body. To send these messages, connections develop between neurons to facilitate communication, and the better the connection is between neurons, the easier and more quickly the message is received and executed.
Our environment and the ways we interact with it affect the neural connections in our brains, and between our brains and the rest of the body. When you do something over and over again, the neural connections associated with that action become stronger and more fixed. When you do something new or in a new way, you develop new neural connections and even new neurons. If you rarely do something, the connections can become weak or even disappear over time [source: Ratey].
Tennis requires the brain to be creative, and it involves planning, tactical thinking, agility and the coordination of different parts of the body. So the more you play tennis, the better and stronger the neural connections related to those types of activities become, and the better you become at them.
In addition to improving neural connections and developing new neurons, studies show that exercises that require a lot of thinking -- such as tennis -- can actually improve brain function in ways that aid memory, learning, social skills and behavior [source: Ratey].