Brain complexity: directed liquid flow in ventricles (Introduction)

by David Turell , Friday, July 08, 2016, 19:16 (3060 days ago) @ dhw

The brain's four ventricles help with brain force movement when the skull is hit. They also supply nutrients and remove waste. Cells on the linings with cilia direct flow:-http://medicalxpress.com/news/2016-07-visualize-cilia-based-networks-brain-vital.html-"We have all bumped our heads at some point, and such incidents are usually harmless. This is thanks to fluid-filled chambers in our brain that offset minor knocks and jolts and provide padding for sensitive components of our nervous system. Cerebral fluid, however, has more than just a protective function: It removes cellular waste, supplies our nervous tissue with nutrients, and transports important messenger substances. How these messenger substances are actually being delivered to their destination in the brain, however, was unclear until now. Göttingen-based Max Planck researchers have now discovered that tiny cilia on the surface of specialized cells could lead the way. Through synchronized beating movements, they create a complex network of dynamic flows that act like conveyor belts transporting molecular "freight". The results obtained by the scientists suggest that these flows send messenger substances directly to where they are needed. -***-"For their experiments, the researchers in Göttingen concentrated on the third cerebral ventricle, which is embedded in the hypothalamus. "The hypothalamus is a very important control center, regulating functions like the circulatory system, body temperature, sexual behavior, food intake, and hormonal balance. To our surprise, there is a sophisticated transport system to and from the hypothalamus for distributing messenger substances via cerebral fluid," -***-"In these images, we can see a complex network of fluid paths inside the cerebral ventricle. However, in contrast to the blood which flows through our blood vessels, these paths are not confined by walls. The exciting question for us was therefore: Is the flow pattern created solely by the synchronized beating of the cilia?" reports Regina Faubel, first author of the study that has now been published in the current issue of the renowned science journal Science. The researchers then filmed the cilia live in action, thus determining the direction of the beating as well as the resulting flows. "Our experiments have shown that the flows are actually generated solely by the movements of the cilia. These act like conveyor belts and would therefore be an ideal means of transporting messenger substances to the right place in the brain," says Eberhard Bodenschatz, Head of the Department of Fluid Dynamics, Pattern Formation and Biocomplexity at the MPI for Dynamics and Self-Organization. "These flows could also help to restrict substances locally, in that the fluid paths flowing against one another could act like barriers," adds Christian Westendorf, second author of the study. -"However, in contrast to the road networks that we travel on daily by car or bicycle, these fluid paths are by no means rigid. To the researchers' surprise, the cilia changed the direction of beating in a temporal rhythm. This came as a big surprise as according to the prevalent school of thought the direction of cilia beating cannot be changed.-"'In the cerebral fluid of humans, there are hundreds - if not thousands - of physiologically active substances," Eichele explains. "We are assuming that the network of flows we discovered plays an important role in distributing these substances. In other experiments, we would like to look at which messenger substances are transported via the flows, and where these are ultimately deposited in the tissue". "But the understanding of the physics of fluid dynamics of cilia is also itself a research objective," adds Bodenschatz."-Comment: Another high complexity arrangement. The brain uses up to 20% or more of our energy consumption. These fluids supply nutrients, take away waste. They also deliver hormonal and other liquid signals which are in addition to electrical signals. Not by chance.