gravity is the main cause to head rush. When you stand
up, some blood collects in your legs and ankles, which can drag down
your blood pressure.
But standing up is a necessary and frequent task, so your body has
built-in mechanisms to counteract that drop in blood pressure: the brain
quickly tells the blood vessels to narrow and the heart to pump harder
in order to move the blood up the body faster. This neurological event
is so quick and automatic, you likely never notice it at all.
Head rush happens when your body cannot respond to your change from a
horizontal to a vertical position fast or well enough. If you’re unable
to counteract the natural drop in blood pressure, less blood will reach
your brain, and that can bring on a bout of dizziness,
light- headedness, blurry vision, or even fainting.
