We try our best to make our material easy to understand. If you want more neuroscience, here are some resources by our colleagues and friends:
Kizoom! is geared toward elementary school students with a brand new book on the function of neurons.
The CK-12 Foundation has an open biology high school textbook with a nice chapter on the nervous system.
The Society for Neuroscience, the largest professional organization of neuroscience, has a free online book aimed at secondary school teachers and students.
If you wants to dive down the rabbit hole, our colleague Eric Chudler at the University of Washington has written brief book reviews of some popular titles in neuroscience.