You know that when you get up quickly and see stars? It is easy to explain.
It is difficult for your body to constantly maintain the blood pressure in the head in a standing position. Our body has a mechanism for this:if you sit down or bend over, the system temporarily works less hard, causing your blood pressure to drop. When you stand up, the system has to start working again. In general, that goes very quickly. However, it can happen that your brain temporarily gets too little blood, which causes the well-known 'stars'.
