During the process of yawning, a coordinated movement of cerebrospinal fluid and venous blood occurs from the brain to the spinal cord, which is a significant difference from deep breathing, where venous blood leaves the brain and cerebrospinal fluid enters. This aspect was revealed during data analysis.
Moreover, yawning increases blood flow through the carotid artery by more than 30% compared to a deep inhalation. Researchers believe that the simultaneous outflow of cerebrospinal fluid and venous blood frees up space in the skull, allowing for an additional increase in arterial blood flow.
Although the volume of fluid moved in a single yawn is only a few milliliters, the effect was equally noticeable in all participants of the experiment. It is worth noting that individual characteristics of yawning were recorded by MRI, showing different patterns of tongue and throat muscle movement.
At this point, the exact mechanism of this phenomenon remains unknown. Scientists suggest that the coordinated action of the neck, tongue, and throat muscles may contribute to the "pumping" of fluid. Possible functions of this redistribution include thermoregulation, removal of metabolic waste, and fine-tuning of brain function; however, these hypotheses require further research.
