The Blood-Brain Barrier Explained

The Blood-Brain Barrier Explained
The diagram above shows how endothelial cells form tight junctions (gaps) to keep harmful particles from passing into the brain from the bloodstream

The blood-brain barrier (BBB) is a selectively permeable membrane that surrounds most of the blood vessels in the brain, that acts as a barrier between the bloodstream and the extracellular space in the brain. It is highly selective and only allows certain substances like water, glucose, oxygen, and small lipid-soluble substances to easily cross from the blood into the brain. This blocks pathogens, toxins, and other potentially dangerous particles from exiting the blood and entering into the brain. The BBB consists of parasitic cells, tight junctions between endothelial cells, and a fibrous extracellular matrix. It is important to have a brief understanding of what the BBB is and how to protect and maintain it. Degrading of this barrier leads to neurodegeneration and brain disease. The whole idea is to be aware and to prevent neurodegeneration.

There are several components to the BBB that make it so efficient. The barrier is in the innermost lining of blood vessels in the brain. It consists of tight junctions between endothelial cells, parasitic cells, and a fibrous extracellular matrix. Parasitic cells are embedded into the cellular membrane and create a thick fibrous basement layer to keep toxins out. To maintain the blood-brain barrier, astrocytes (brain cells) further tighten the junctions. This is demonstrated in the top diagram above. These astrocytes have “astrocytic feet” that project onto the walls of blood vessels and signal the endothelial cells to form these tight junctions. This restricts diffusion of harmful particles across the membrane. Maintaining a healthy inner lining of blood vessels is absolutely crucial to optimal function of the blood-brain barrier.


Lipid-soluble molecules and low-weight molecules are able to cross the BBB. The barrier uses invasive and noninvasive ways to transport nutrients, drugs, and other molecules. Glucose, water, oxygen, alcohol, THC, nicotine, and caffeine are able to cross the blood-brain barrier. Most infections aren’t able to cross; however, some are able and can be deadly if not treated. Most medications are not able to cross the BBB, which presents a major challenge in treating neurodegenerative disease and brain infections. Luckily, toxins, foreign substances, and most infections cannot cross the blood-brain barrier.


Protecting the blood-brain barrier (BBB) and maintaining the integrity of it, are crucial for optimal function. Damage to this barrier can eventually lead to a leaky BBB, which can lead to brain fog, memory loss, depression, and inflammation in the brain. The blood-brain barrier can be repaired if damaged; however, it is important to know how to prevent and limit disturbances in the BBB. It is important to realize that chronic low-grade inflammation in the brain will slowly, but surely degrade the blood-brain barrier. This inflammation over time will lead to an overall weaker, leakier BBB, allowing toxins, immune cells, cytokines, and other harmful particles to enter into the neural tissues. Thus, furthering increasing neurotoxic substances, brain pathologies, and brain inflammation. Metabolic syndrome, insulin resistance, diabetes, hypertension, high cholesterol, and obesity can all lead to a leaky barrier and chronic systemic low-grade inflammation. And overtime, this can all lead to neurodegenerative disease, chronic sleep disorders, and psychiatric disorders. One of the most effective ways to maintain and strengthen the BBB is through exercise. Get up and M O V E.

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