Engaging the core could regulate blood flow in the brain

Engaging core muscles—through movement, exercise or even coughing—may be a key regulator of blood flow in the brain. When the body moves, the contraction of abdominal muscles increases pressure in blood vessels connected to the brain through the spinal column. A new study by researchers at Penn State shows that the increased pressure creates ultrafast constrictions of major veins in the brain, momentarily increasing blood flow.

Understanding how the regulation of blood flow in the brain is influenced by movement in the body could help explain the connection between exercise and brain health or why migraines and headaches can become more severe with movement, according to the research team.

The paper describing the research, which was conducted in mice, appears this week in the Proceedings of the National Academy of Sciences.

Everyday behaviors constantly change the mechanical state of the body. Walking, running or involuntary movements, like breathing or coughing, can change pressures throughout the body, the researchers said. This work, the team said, identifies a previously underappreciated aspect of normal brain physiology—blood flow is not only regulated by local signals but is connected to movement elsewhere in the body—and provides a new framework for understanding how the brain and body interact.

“The brain may be protected inside the skull, but it is not isolated from the mechanical forces generated by the rest of the body,” said Qingguang Zhang, who was an assistant research professor in engineering science and mechanics at Penn State when the research began and is now an assistant professor of physiology at Michigan State University and the paper’s first author.

Veins respond to movement

“We were surprised by how rapidly and consistently the veins responded to movement. The brain is often studied as though its circulation is regulated independently of the rest of the body. Our findings show that mechanical signals generated by the body can have immediate consequences for the circulation inside the skull.”

While the research was conducted in mice, the team explained that the physiological structures are extremely similar in humans. They said they suspect that the relationship between abdominal contraction, movement and blood flow in the brain is similar in humans as well.

Patrick Drew, professor of biology, engineering science and mechanics, neurosurgery and biomedical engineering at Penn State and leader of the research team, compared the connections to a city’s water system.

“A city’s water system has to be able to accommodate different use needs of an apartment building or a single-family home, or even a full stadium on gameday,” Drew said. “Blood flow in the body must be precisely controlled because different organs need different amounts of blood at different times.”

Blood flow requires fine control

Within the brain, for example, active areas need more blood than parts of the brain that aren’t currently being used. This fine control is accomplished using three types of blood vessels: arteries, capillaries and veins. Arteries carry oxygenated blood from the lungs to capillaries, the tiny blood vessels that exchange oxygen and other nutrients for carbon dioxide and waste products from cells and organs. The blood then returns to the lungs in veins to start the process again.

“Arteries and capillaries are surrounded by muscles that can contract to control how much blood passes through them, and because of this, they are generally thought of as the main regulators of blood flow,” said Drew, who is also associate director of the Huck Institutes of the Life Sciences at Penn State.

“If a region of the brain needs more blood, it can send a chemical signal to arteries and capillaries that tells them to relax and increase flow. Veins have fewer muscles, so we were surprised to see extraordinarily fast constrictions of the superior sagittal sinus, the large vein that runs along the top of the brain, and the bridging veins that feed into it.”

Abdominal contractions drive vein changes

The team observed that the constriction of veins in the brain was correlated with activation of abdominal muscles that occurs during normal movement in mice. In a previous study, the team had shown that abdominal muscle contraction can cause changes in pressure in the body that gently move the brain, helping to circulate the cerebrospinal fluid that surrounds the brain.

The new study established a direct connection between the abdominals and the regulation of blood flow in the brain, demonstrating that veins actively participate. While constriction of arteries occurs on the time scale of a second or several seconds, the veins constricted much faster, within about a tenth of a second, in response to abdominal muscle use.

“Veins are not simply passive pipes,” Zhang said. “When we think about brain blood flow regulation, we tend to focus heavily on arteries. Our results highlight the other side of circulation. What happens to blood as it leaves the brain can be just as dynamic and physiologically important.”

Potential links to headaches

These veins are located in the membrane that surrounds and protects the brain, called the dura. The researchers explained that while the brain itself does not have pain receptors, there are pain receptors in the dura that are thought to be associated with headaches and migraines that could be influenced by movement and blood flow.

“We are interested in understanding the fundamental mechanisms that control the flow of blood in our brains,” Drew said. “Like a good mechanic must understand how a car works in order to diagnose and fix a problem with its engine, we want to understand blood flow in the brain so, in the future, it will be easier to recognize issues and potentially develop treatments and cures.”

In addition to Drew and Zhang, the research team included C. Spencer Garborg, a postdoctoral researcher in Drew’s lab; Noah Frank, who earned his bachelor’s degree in mechanical engineering at Penn State; Fatemeh Salehi, a graduate student in biomedical engineering at Penn State; and Kevin L. Turner, who earned a doctoral degree in biomedical engineering at Penn State.

Who’s behind this story?

Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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