What happens when blood goes to the head when your up-side down?

When you are upside down, gravity causes blood to pool in your head, leading to increased pressure in the cranial region. This can result in a sensation of fullness or pressure, and in some cases, may cause headaches or dizziness. The body usually compensates by adjusting blood flow and pressure, but prolonged inversion can lead to discomfort or other symptoms. Overall, the body's regulatory mechanisms work to maintain balance, but being upside down for extended periods is not typically sustainable.