Under-appreciated – the other type of brain cell

This post is dedicated to a hard-working friend with a Napoleon complex. And by Napoleon complex I mean she is obsessed with Napoleon. And Glial cells. She sent me a link the other day…

As with most others taught about the brain, our neuroscience lectures started out by telling us that there were, broadly speaking two types of cells in the central nervous system (that which is encompassed by the brain and spinal cord). You’ve got the neurons: electrically excitable cells that is able to transmit information from one point to another very quickly. They also integrate information from different sources, form networks to accomplish complext tasks such as breathing, digestion, walking and of course thinking. They’re pretty clever little buggers. Along with these busy little think-cells are other cells, called glia (greek for glue).

Look at the pretty glia!

Glia stained in the cerebellum

There are numerous different types with different functions: oligodendrocytes wrap fatty insulating material around brain cells, while Schwann cells do the same to neurons that project outside the brain. Astrocytes remove excess neurotransmitter following synaptic transmission, regulate the ionic environment and also appear to regulate blood supply. Microglia are immune cells. Ependymal cells make cerebrospinal fluid. Enteric glia take care of neurons in the digestive system in much the same way that astrocytes do in the brain. There is much still to learn about them.

For a long time these pretty little glia were considered nothing more than glue. Their full importance had not been appreciated for a long time. Glia provide nutrients for neurons, insulation that allows for optimal signal transmission and maintain the environment. That environment needs to be maintained within a very small range, the smallest disruption in chemical composition can have catastrophic consequences for the neurons in the surrounding area.

Nice picture showing neurons and glia.

Neurons are labelled in green the glia are stained red.

When the function of glia is impaired severe debilitating diseases emerge. For example, in multiple sclerosis, the glial cells surrounding neurons in the brain and spinal cord get attacked by the immune system, leading to debilitating symptoms including dizziness, tiredness, pain, tingling and sight problems. Recent advances in ALS (Amyotrophic lateral sclerosis; Lou Gehrig’s disease) suggest that glia in the spinal cord have an important role in this progressive degenerative motoneuron disease. Furthermore, it looks like glia also have a role in Alzheimer’s disease. Pretty exciting for a group of cells that were only thought of as glue for a hundred years.

Below is a diagram depicting the relationship between glia and neurons.

The glia provide nutrients and maintain the neuronal environment