Giraffe have unusually high heart rates for their size, at 150 beats per minute. When the animal lowers its head the blood rushes down fairly unopposed and a rete mirabile in the upper neck, with its large cross sectional area, prevents excess blood flow to the brain. When it raises again, the blood vessels constrict and direct blood into the brain so the animal does not faint. The jugular veins contain several (most commonly seven) valves to prevent blood flowing back into the head from the inferior vena cava and right atrium while the head is lowered. Conversely, the blood vessels
Incognito: The Secret Lives of the Brain the Colbert Report. Incognito: The Secret Lives of the Brain Incognito: The Secret Lives of the Brain is a New York Times bestselling non-fiction book by American neuroscientist David Eagleman, an adjunct professor at Stanford University. "If the conscious mind - the part you consider to be you - is just the tip of the iceberg, what is the rest doing?" This is the main question throughout the entirety of the book. In "Incognito", Eagleman contends that most of the operations of the brain are inaccessible to awareness, such that the conscious mind "is like a stowaway on a transatlantic