auto in this case means "self" I think.
It seems to be describing an immune disorder or allergy that's attacking this particular signal pathway. Based on the article, the antibodies glomp onto the receptors that should control the relaxing and contracting of the blood vessels, leading to a "usually loose" or "slow tightening" of the vessels because they just don't get the "time to tighten up" signal properly after the "switches" that are supposed to get the signal are eaten/attacked by their own body. Severe patients probably also had swelling of the legs/hands and moisture retention in the limbs.
Basically; They'd stand up, their blood would drop away from their brain and into their lower body, and the signal to "crush that blood back up into the brain" wouldn't get though fast enough leading them to just pass out from lack of oxygen.
You "can" train yourself to somewhat control the blood flow to your limbs, but it's more a reaction to the way you control your conscious muscles: Tighten your muscles groups and hold it for 5-20 seconds depending on your fitness level one at a time; like like hands, then arms, then shoulders, then upper body, then midriff/lower back, then pelvis area, then butt and thighs then calvs, then toes. Just long enough you "feel" the tightness get uncomfortable. once you relax they will relax more fully than their natural rest-state and (in normal people) your blood pressure will also drop as the vessels also relax to replenish ATP. With practice you can do it pritty much on command without much prep-time at all. Inverse is true where if you consiously tighten your muscle groups a bit you can force blood where you want it. Iron Shirt martial arts techniques, and the g-force techniques of fighter pilots use it too.
Edited by GAHD, 12 September 2019 - 01:15 PM.