Nervous systems vary in structure and complexity. There are several types of glia that serve different functions. In a cnidarians, nerve cells form a decentralized nerve net.
Glial cells of the b peripheral nervous system include Schwann cells, which form the myelin sheath, and satellite cells, which provide nutrients and structural support to neurons.
Glia are non-neuronal cells in the nervous system that support neuronal development and signaling.
Satellite glia provide nutrients and structural support for neurons in the PNS. The nervous system is made up of neurons, specialized cells that can receive and transmit chemical or electrical signals, and glia, cells that provide support functions for the neurons by playing an information processing role that is complementary to neurons.
Glia can be compared to the workers at the electric company who make sure wires go to the right places, maintain the wires, and take down wires that are broken.
This is distinctive from the PNS where a single Schwann cell provides myelin for only one axon as the entire Schwann cell surrounds the axon. Dendrites can have small protrusions called dendritic spines, which further increase surface area for possible synaptic connections.
A pseudounipolar cell has a single process that extends from the soma, like a unipolar cell, but this process later branches into two distinct structures, like a bipolar cell. A neuron can be compared to an electrical wire—it transmits a signal from one place to another.
But neurons are also highly specialized—different types of neurons have different sizes and shapes that relate to their functional roles.