Fluid dyanamics

Courtesy of reference 1, I have been thinking about what might be involved in suspending a working brain in some kind of vat. A working brain in or connected to some sort of life support system.

Which led me to think about blood supply, something which the brain, being rather a busy object, needs rather a lot of. A plentiful, steady and reliable supply. So we imagine some sort of blood engine, perhaps a bit like the gas boiler in our hot water system, supplying a tank and then some kind of blood pump, perhaps a bit like the pump in our airing cupboard which pumps the hot water around the radiators. Now, in the case of the hot water system, the only water property of interest is its temperature and we are quite comfortable with the idea that while the boiler and the pump do their best to keep the water at a uniformly high temperature throughout the system, in practice they are going to fail and the temperature of the water will vary - and in some outlying parts of the system the water will be quite cool.

So what about blood, rather more complicated from a chemical point of view than water, and with which the brain interacts, both taking stuff out and putting stuff in? A taking out and putting in that occurs throughout the brain, not just at one or two refuelling points. The water towers that you used to get at strategic points along the railway line.

So to what extent is the chemical composition of the blood going to be the same everywhere? Can we regard that composition as a given, at least from the point of view of thinking about how the brain works?

Clearly this composition is not going to be the same at all places and at all times; replenishment cannot be instantaneous. But do the considerations of scale touched on at reference 2 mean that we can neglect all these messy details? Sadly, I suspect that the answer is no and that the brain in the vat is unlikely to work very well. We cannot usefully detach the brain from the body, not even in a thought experiment.

Getting worse, maybe one should think of the blood system as being an information system in its own right, carrying chemical messages around both the brain and the body. Interacting with the presumably bigger and more complicated information system implemented by the billions of neurons. But who is in charge of that carrying? Who is in charge of reading and writing the messages?

Clearly time for breakfast.

Reference 1: https://evanthompsondotme.files.wordpress.com/2012/11/cosmelli-and-thompson-enaction.pdf.

Reference 2: http://www.psmv2.blogspot.co.uk/2015/08/the-freudians-fight-back.html.