What actually happens when parts of the brain become active? Nerve cells called neurons in active parts of the brain communicate with each other more. The active parts of the brain require more oxygen to allow neurons to communicate. How do the active parts of the brain get a fresh supply of oxygen? The blood carries oxygen, through the blood vessels, into the brain. There is a protein in the blood called hemoglobin that holds onto oxygen and carries it to places that need more energy. When hemoglobin is holding onto oxygen, it is called oxygenated hemoglobin, and when hemoglobin is not holding oxygen, it is called deoxygenated hemoglobin. When an area of the brain is active, oxygenated hemoglobin starts to displace the deoxygenated hemoglobin.
When a part of the brain is active, there is a hemodynamic response. A hemodynamic response happens when the blood vessels in the active areas of the brain become wider.

License information: CC BY 4.0
MPAA: G
Go to source: https://kids.frontiersin.org/article/10.3389/frym.2019.00086