There are also trillions of support cells in our brains they are collectively called glia, there are then several types of glia that have specific purposes. Neurons may be the more important cells in the brain that relay messages about what you're thinking, feeling, or doing, but they couldn't do it without a little help from their friends, the glial cells. There are several kinds of glial cells, Oligodendrocytes, Microglia, and Astrocytes are a few of these. Oligodendrocytes are glia cells that help with a neuron's action potential, they wrap tightly around the neuron axons and form the myelin sheath. This helps speed up the action potential as it travels down the axon to the synaptic gap. Without the myelin sheath the action potential would travel up to 30 times slower. The next one is the Microglia these are very important to our brain's health. They are immune cells found only in the brain, and their job is to eat foreign invaders such as bacteria and viruses. Finally, Astrocytes are actually involved in how signals travel between neurons. They are star shaped glia that hold the neurons in place, and supply nutrients. They actually can communicate with a neuron and this can modify the signals that a neuron sends and receives.