Fast heart rates, tachycardias, can also cause syncope/nearsyncope because the heart is unable to fill adequately with
blood to pump to the brain. Orthostatic hypotension (
blood vessels cannot constrict when standing up, therefore causing pooling of blood in the legs-->not enough blood to the brain).
Another cause can be a seizure, in which you lose all muscle tone. This is usually due to too much electrical activity in a certain area in the brain.