Thus, extra blood is pumped into the astronauts head. In the human, their cardiovascular system must push blood from the heart to the head. In giraffes, their hearts are 2 meters below their heads. Thus, they must maintain high blood pressure to push the blood to their heads. A giraffe s blood pressure is 260mmHg at the heart.
Giraffes also have a massive heart and vascular system to deliver sufficient blood to the brain.
We expect snakes to have a low blood pressure because snakes are always lying on the ground and thus do not have to counter a vertical gradient. Yet, there are some snakes that climb trees and thus must fight against a vertical pressure gradient. An experiment was conducted where the relative blood flow to the head was compared between tree climbing snakes and ground dwelling snakes. The snakes started out lying horizontally and were then tilted from an angle of 0 degrees to 90 degrees. Tree climbing snakes continued to have blood flow to their head at around 100mmHg.