Yesterday garner was reading about the human nervous system. he knew it was a communication network that conveys messages throughout the body, but he did not realize it was made up of as many as 100 billion

The answer is neurons.

The nervous system is a network that made by neurons. Neurons have a feet-like organelle called axons that connect them with each other. These allow the brain to be connected with a muscle or any organ that located far away. The connection need many cells which makes them have a high cell count.