Where’s Your Head At?

The Immune-Brain Connection 


When studying the processes that cause depression, cognitive decline, Alzheimer’s and neurodegeneration, the immune-brain connection is essential.

The brain is composed of nervous tissue.  Nervous tissue is composed of neurons and glial cells.  Now, we have all heard of neurons, right.  Neurons are ‘nerve cells’ that transmit chemical and electrical impulses.

Glial cells on the other hand are definitely less familiar.  In fact, early on in their study very little was known about their function. Glial cells were thought to just help neurons attach together.  And that is where the name ‘glial’ comes from: it is the Latin word for ‘glue.’

It is now known that glial cells do a lot more than stick neurons together.  They are the immune cells of the brain.  Glial cells actually assist in the broadcast of nerve impulses, provide nutrients to neurons, form myelin, help maintain homeostasis and provide support and protection for neurons. 

Interestingly, there are 10 times MORE glial cells in the brain than there are neurons.  Glial cells are the most abundant cells in the brain, and constitute half of the overall mass of the brain.

This is the important thing to understand about glial cells from a brain health standpoint … anytime the glial cells are activated, then neuroinflammation and neurodegeneration can occur.

There are three types of glial cells: microglia, astrocytes and oigodendrocytes.


Astrocytes help form the blood-brain barrier, provide metabolic support to neurons and assist in repair of injured tissues in the central nervous system.  The blood-brain barrier separates the brain and spinal cord from the rest of the body.  It allows oxygen, carbon, dioxide, fatty acids, ethanol, steroid hormones and some amino acids and sugars to pass through.  And it keeps everything else segregated.  For example, neurotransmitters made in the brain, stay in the brain.  Antibodies made in the body, stay in the body.


Oigodendrocytes insulate axons with myelin. Myelin is the fatty covering on nerve fibers, it helps increase the speed at which impulses are conducted.


And the microglia serve as the main immune system for the central nervous system.  Microglia are distributed throughout the brain and spinal cord, constantly circulating, surveying and scavenging. 

Macrophages in the peripheral nervous system and microglia in the brain are very similar in function.  You’ve heard of macrophages, they are the white blood cells that remove dead or dying cells, cellular debris, and pathogens.  They are known as the ‘big eater’ cells because they essentially engulf and digest their quarry.

Microglial cells also engulf and digest foreign material, but they are more sensitive than macrophages.  This is because antibodies cannot cross the blood-brain barrier effectively.  To compensate microglial cells are designed to be ‘more responsible.’  They scavenge, phagocytosize (devour), cytotoxicize (poison), present antigens (tag), strip synapses (clean), and promote repair.

Microglia are constantly searching the brain and spinal cord for damaged or dying cells, neural tangles, DNA fragments, plaques and substances that provoke an immune response.  When a microglial cell finds any of these it will activate and destroy the compound.

Microglia do not destroy by solely engulfing and digesting their quarry, they can also release hydrogen peroxide and nitric oxide to promote cellular damage and secrete proteases to digest cellular proteins.  They also secrete glutamate and aspartate as part of their defense mechanism.

The thing is, when the mighty microglia are activated they produce significant amounts of collateral damage to surrounding neurons … and this is what promotes neuronal injury and degeneration that manifests with symptoms like depression, cognitive decline, or Alzheimer’s.

To maintain brain health, it is really good to know what activates microglia.  There are actually quite a number of things that can activate microglia.  Have you ever heard of cytokines?  Cytokines are cell-signaling proteins and they readily cross back and forth through the blood-brain barrier.  Many of the cells in our immune systems produce cytokines.  So anything that causes the immune system to flare will result in cytokines being released and eventually making their way to the central nervous system, activating the microglia.

Microglia can be activated by any substance that crosses the blood-brain barrier and causes an immune response, not just cytokines.  Microglia can also be activated by increased extracellular potassium (from sickly or dying neurons), elevated glucose (Syndrome X, Type I & II Diabetes), activation of the gut-associated lymphoid tissue (immune response in the digestive tract, like food sensitivities or IBS), and activation of the bronchial-associated lymphoid tissue (immune response in the lungs, like airborne allergens or pneumonia).

This is why an anti-inflammatory diet, repairing the integrity of the digestive system and modulating the immune response has such a profound positive effect upon brain function.

Brain function is important to EVERYONE regardless of age.  Peak performance in career, sports, hobbies and relationships depends upon a healthy brain.


To get an idea about how your brain is functioning you can start by asking yourself these questions:


Is your memory noticeably declining?

Are you having a hard time remembering names and phone numbers?

Is your ability to focus noticeably declining?

Has it become harder for you to learn new things?

Do you have a hard time remembering your appointments?

Is your temperament generally getting worse?

Is your attention span decreasing?

Do you find yourself down or sad more often?

Do you become more fatigued when driving compared to in the past?

Do you become more fatigued when reading compared to in the past?

Do you often pick up your cell phone and forget why?

Do you find yourself walking into a room and forget why?


If you answer yes to any of the above questions, there is definitely some neurodegeneration occurring.  The good news is that A LOT can be done about it.

If you or someone you love has noticed symptoms related to general brain health, then approaching the issue from the perspective of nutritional therapy can really, REALLY help.

Be sure to check out the rest of the website to learn more about the nutritional coaching process and contact me with any questions.

As always, 

Many Blessings and Cheers!

Vanessa Hendley


I’d love to hear about your biggest “aha!” moment from today’s blog, and how you’re going to implement its wisdom into your life.  Just drop a comment via email

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