Knowledge gained during Henry Hudson's four voyages significantly expanded on that from previous explorations made in the 16th century by Giovanni da Verrazano of Italy, John Davis of England and Willem Barents of Holland.
You are really asking three questions; Your brain begins to die after 4-6 minutes without oxygenated blood being delivered to it. If your blood is flowing out from a wound that causes a few things to happen...less blood is delivered to organs, therefore less oxygen and eventually you will bleed out and that's it.
When you have an ischemic stroke, the oxygen-rich blood supply to part of your brain is reduced. With a hemorrhagic stroke, there is bleeding in the brain. After about 4 minutes without blood and oxygen, brain cells become damaged and may die.The body tries to restore blood and oxygen to the cells by enlarging other blood vessels (arteries) near the area.ith a hemorrhagic stroke, there is bleeding in the brain. After about 4 minutes without blood and oxygen, brain cells become damaged and may die. The body tries to restore blood and oxygen to the cells by enlarging other blood vessels (arteries) near the area.