Does blood pressure increase during a deliberate period of focus?
My reason for formulating this hypothesis is personal experience.
A simple example is when I work, sitting, at the PC. Let's say I work 25-45 minutes. When I am working my breathing becomes more shallow and it's always through my nose. Then, when I've completed the work I usually, automatically, take a deep breath ... as I physically feel relieved it's over even if it's work I enjoy. Then I notice I am a tiny bit lightheaded and, as I feel relieved, and I don't particularly want to get up, I usually have a desire to surf the web.
So, I'm wondering if concentration causes blood pressure to increase, which then quickly reduces when I'm done with my task, which is causing this feeling I am describing as lightheadedness. Alternatively is the blood pressure change related to the reduced breathing as I focus? ... is there such a thing?