Thank you so much for your informative answer. So does that mean that the BP in my brain would remain relatively constant even while straining very hard in the bathroom for instance? Thanks
The brain does not regulate blood pressure. There are biological sensors in both the left and right carotid arteries that measure both oxygen and carbon dioxide levels simultaneously. These control the heart rate, which in turn controls blood pressure. When you are conspitated and strain on the toilet the blood pressure is lowered because the vagus nerve is stimulated. This drops the heart rate. This nerve is one of the largest in the human body and meanders throughy the system and is in close proximity to the anal sphincter.