Science Shows Us How The Blood-Brain Barrier Works

The brain has a barrier that is like a wall of cells, and this barrier protects the brain from things in the blood.

The BBB allows certain molecules to pass through easily, like oxygen and carbon dioxide. This allows the cells in your body to work properly. (1)

It also keeps out larger particles and unwanted molecules that could cause problems.

This selective permeability of the BBB is critical for regulating the composition of fluids in the brain.

So, to keep fluids in the brain at optimum levels, the blood-brain barrier has special mechanisms that let different substances through.

The presence of ions within the extracellular compartment between neurons, such as sodium and potassium, plays a major role in supporting cell membrane potentials and nerve impulse transmission, which supports brain function.

Ions are important in the cells that make up your brain. They help provide a difference in the electric charge between the two sides of a cell. (2)

This helps support messages going to other cells and nerves and also helps to keep your brain healthy.

The BBB is present at all levels in the central nervous system (CNS), with the exception of the circumventricular organs, including the pineal gland.

This barrier is very selective in regulating the movement of substances from the blood into brain interstitial fluid.

A unique property of the blood-brain barrier is that it prevents large molecules from getting into the brain, which would affect normal brain function.

Brain Protection

Since the cerebral spinal fluid is liquid and can’t cross the blood-brain barrier, it circulates in the space between the cells that make up your brain.

This means that substances within the body’s immediate vicinity easily alter it.

It contributes to homeostasis by ensuring a consistent circulation of nutrients into different parts of your cells and removing any substances created by those processes. (3)

Cerebral spinal fluid also has its own defenses against infectious agents like viruses and bacteria.

In addition to acting as an immune defense agent that prevents pathogens from infecting you, it also contains special proteins that help carry messages through your nervous system from one part of the body to another.

Endothelial Cells

The main cell that makes up the BBB is called an endothelial cell.

Endothelial cells are essential because they help form blood vessels in your body. They also help prevent many foreign molecules from entering your brain and spinal cord, so it stays healthy.

The endothelial cells of the BBB are in many blood vessels that surround your brain and spinal cord. These cells help make up all different types of blood vessels, from tiny capillaries to large arteries.

The endothelial cells are special because they do not allow many molecules or ions to pass through them. This makes it harder for substances to enter the brain from the bloodstream.

Endothelial cells are also very flat and close together, creating a barrier that keeps different substances from passing into the tissue. Each of these cells only lets needed substances through.

The BBB controls the entry of substances from your blood into your brain in a very specific way, depending on which substance you are talking about.

Some things can easily pass through, while others cannot.

The Importance Of A Healthy Blood-Brain Barrier

A healthy blood-brain barrier is important for protecting our brain cells from harmful substances that may cause damage.

If the barrier becomes unhealthy, we are more vulnerable to having problems with memory, balance, and other things. (4)

The endothelial cells of the blood-brain barrier also help form blood vessels in our body which are necessary for good health.

When it comes to the blood-brain barrier, many things change as we age.

This includes a buildup of things like cholesterol and fat, which make up the cells that form the blood-brain barrier.

In addition, changes in our immune system can cause problems with how well our body can fight infection or remove harmful substances.

As we get older, certain things can cause the blood-brain barrier to become tighter and allow less helpful substances into our brain.

This can include diseases or medical conditions in addition to aging itself.

Causes Of Impaired Function

I mentioned that as we age, the blood-brain barrier becomes tighter, and less helpful substances enter our brains.

With this, certain things can cause the blood-brain barrier to become tighter.

One of the most common diseases that cause problems for the BBB is Alzheimer’s disease.

With Alzheimer’s disease, it is believed that plaques containing proteins called beta-amyloid build up in the space between your brain cells which interfere with how well your BBB works. (4)

This makes it harder for helpful substances to enter your brain and also allows harmful substances to get inside more easily.

Another disease that can cause problems for your BBB is multiple sclerosis.

Multiple sclerosis causes a disorder in the protective covering of your nerves called myelin. (5)

There is a lot that we still do not know about multiple sclerosis, but it is thought that the loss of this myelin causes problems with the BBB and nervous system damage.

Treatment For Impaired Function 

An impaired blood-brain barrier can be treated with a variety of different techniques and medications.

One treatment for an impaired blood-brain barrier is the administration of intravenous fluids.

This is done by placing a needle into the vein and then slowly injecting a liquid solution of saltwater and glucose into the bloodstream.

This creates more fluid which in turn creates more space between the endothelial cells. The liquid acts as a temporary seal to make it harder for harmful substances to enter the brain.

Another treatment for an impaired blood-brain barrier is immunotherapy which has been effective in specific conditions like chronic allergic asthma, rheumatoid arthritis, and ulcerative colitis.

To administer this therapy, physicians will inject a small amount into the patient to introduce their immune system to the substance it is reacting to.

This allows the immune system to slowly learn how to recognize and stop reacting to the harmful substance while still allowing helpful substances through.  

In addition, this also helps with any inflammation that may occur within your brain, which can cause further problems for your BBB.

If you have an infection that is affecting your BBB, your doctor may prescribe medicine to fight the infection off.

It may also be a good idea to get treated for any other underlying conditions you may have.

Some treatments used to help treat impaired function in the blood-brain barrier include: 

  • Antibiotics for infections like Lyme disease
  • Immunosuppressants that help your body fight off infections
  • Drugs or supplements to lower cholesterol levels, blood pressure, or other heart conditions
  • Drugs to help prevent blood clots.

If you have a disease like diabetes, high cholesterol, or high blood pressure, your doctor may treat you with medicine to fight off the disease and make it easier for your brain to function normally.


The blood-brain barrier is a system of cells that protects the brain from potential dangers.

It prevents many substances in your bloodstream, like ions and molecules, from entering into the fluid between cells where neurons reside because it does not allow these things through its endothelial lining.

If this protective membrane becomes weak or damaged due to other conditions such as high cholesterol levels and diabetes, you may be at risk for infection in your brain, which will impair functioning within the BBB even more so than before.

If you suffer from a disease that makes it harder for vessels in your brain to function properly, you may be more prone to an infection entering the fluid between cells.

In these cases, your doctor may prescribe antibiotics or other drugs to treat the infection and help protect your blood-brain barrier.

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