Through the Open Window: How Does the Brain Talk to the Body?

Abstract

The brain controls the activities of the body, including food digestion, drinking, sleep cycles, temperature, blood pressure, and more. These functions are essential to keep the body in homeostasis, which is the state of being steady and balanced. To control homeostasis, the brain talks to the body with the help of chemical messengers called hormones. Hormones travel through the blood stream from the brain to the body and back. However, in order to protect the delicate brain cells from unwanted intrusions, the blood vessels of the brain are tightly sealed, preventing the passage of most molecules. How, then, does the brain bypass this barrier to communicate with the body? The answer is that, in certain parts of the brain, the blood vessels contain special window-like openings that allow passage of hormones. Scientists are investigating why and how some blood vessels open their windows while others remain sealed.