How does stress cause symptoms of Low Blood Pressure to occur?

Please can someone tell me, I have tried asking before but got no reply that actually told me how it happens?
If you already have Low Blood Pressure, but in a healthy way so you get no symptoms. Then when you get stressed or upset you suddenly get symptoms for a while, how does that work, what does the stress do to make the symptoms start.
When I say symptoms I mean, light-headedness, dizziness, weakness and fainting.

The reason you've had no sensible answers is that scientifically, "low blood pressure" doesn't exist. There is no such thing as "low blood Pressure" -except in the minds of the medical profession.

Whatever your doctor says, you haven't got low blood pressure.
So let's start again, shall we?

Our hearts all develop the correct pressure to drive the correct amount of blood round your body. (Unless you're old and dying of course).
What happens to some individuals (who believe, -or keep getting told, by their doctors that they have 'low blood pressure') is that the mechanism which controls and keeps track of the variations in flow of blood needed (when rising from a chair for instance, or getting out of bed, -or even bending down then straightening up) is impaired for some reason ..- typically hormonal imbalance, but not necessarily.
So the pumping action of the heart is distorted and momentarily the brain doesn't get the correct supply of blood. It soon clears, usually, but obviously the severity of the impairment varies from person to person

If you're a young girl, it's a frequent occurrence and 99% grow out of it..

That's the top and bottom of it. Hope it helps?

I too have low blood pressure and so does my sister but not as you say "but in a healthy way so you get no symptoms" as far as I can tell everyone with low blood pressure gets those symptoms, that is usually how they know that they have low blood pressure!