Understanding the “hard” problem of consciousness involves understanding physiology and understanding as much as possible about “Blood Flow, Blood Pressure, and Resistance”. The relationship between blood volume, blood pressure, and blood flow is intuitively obvious. Water may merely trickle along a creek bed in a dry season, but rush quickly and under great pressure after a heavy rain. Similarly, as blood volume decreases, pressure and flow decrease. As blood volume increases, pressure and flow increase.
You can have too little blood flow going to an organ, or too much. People tend not to worry about “too much” blood flow to the digestive system increases in order to break down the food and absorb nutrients. That is usually a “natural” think and a good thing. The blood can deliver extra oxygen and nutrients to the different parts of the body at different times….. For example, when we eat, blood flow to the digestive system increases, in order to break down food and absorb nutrients. Exercise increases blood flow to the muscles in a controlled manner so that all bodily systems benefit. These are complicated processes and researchers are still trying to understand them. Exercise is particularly complicated. Paula and I are mainly interested in the brain and it seems that the current understanding is that…. As cardiac output rises with exercise, brain blood flow remains constant (or increases slightly) while blood flow to the heart increases to meet the increased demands for myocardial blood flow that are primarily associated with exercise-induced increases in heart rate. Regulation of Increased Blood Flow (Hyperemia) to Muscles During Exercise: A Hierarchy of Competing Physiological Needs Michael J. Joyner and Darren P. Casey Physiol Rev. 2015 Apr; 95(2): 549–601. doi: 10.1152/physrev.00035.2013 www.ncbi.nlm.nih.gov › pmc › articles › PMC455121
Hyperaemia to the muscles is also the basis of the Flight or Fight Response, where in response to the activation of a number of things, the sympathetic nervous system, vasodilators, hormones, etc… blood flow to the muscles is increased in order to be able to fight or flee the [hypothetical] lion.
I imagine that during exercise or the “fight or flight response” brain blood flow must be carefully kept stable as much as possible in order to to be able to “think” of stuff like how to avoid injury while exercising or, in the case of meeting with a real Lion, a person needs to have the presence of mind to think of where to flee or when and how to fight. Yup some of us can fight lions….see “How a Man Killed a Mountain Lion with His Bare Hands” OK the mountain lion was a cub, about 3-8 months old , they think….but still!!!!! https://www.outsideonline.com/2389231/how-man-killed-mountain-lion-his-bare-hands
But I digress.
The point is blood flow to the brain is controlled a little differently because the brain is encased in bone and cannot be allowed to swell too much or it will get squished or compressed and that is not good.
to be continued……[I have a lot to say about this] and about hyperaemia and “passive ” chronic hyperaemia ………….stay tune!!!