Short answers, pulled from the story.
Nervous tissue first arose in wormlike organisms about 550 to 600 million years ago. This emergence marked a turning point for animal life, allowing creatures to coordinate actions and sense environmental changes with precision.
Sponges remain the only multicellular animals without any nervous system at all. They lack synaptic junctions connecting their cells yet possess homologs of genes that play key roles in synaptic function.
In vertebrates, the nervous system divides into two main parts: the central nervous system and the peripheral nervous system. The central nervous system consists of the brain and spinal cord while the peripheral nervous system comprises nerves connecting the central system to every other body part.
It was not known that neurons are the basic units of the brain until approximately year 1900 according to Santiago Ramón y Cajal. His work established the neuron as the fundamental building block of neural architecture.
Glial cells provide structural and metabolic support maintain homeostasis form myelin and participate in signal transmission. A very important type of glial cell generates layers of fatty substance called myelin that wraps around axons allowing action potentials to transmit much more rapidly and efficiently.