The things that are clearly innervated, like your mouth (there are three big fat nerves keeping watch there), don't appear to be necessary for consciousness. You don't need a mouth to enjoy Beethoven. You don't need your digestive track. We can put the right chemicals straight into your blood.
You don't need a heart or lungs. We can bypass those with machinery and you can remain wide awake. — frank
You may be missing the point. It’s not a question of what’s necessary for the very existence of consciousness, but of how feedback from nerves in the mouth or the other organs contribute to the particular way in which consciousness functions. You can keep a heart alive outside of the body , but not without changing its functioning significantly. The heart will never function exactly the same way it did when it was part of the body, no matter how many apparatuses you hook it up to, and especially if you transplant it into a different body. What if we transplanted a brain to it a new body? Would this profoundly alter conscious experience : what we think and how we think and feel? It would certainly have an effect , but a minor one , because the brain is essentially most of what the body is in terms of functional complexity, not just in terms of number of neurons but what the neurons do, how intricately they interact with each other.
The functioning body , and consciousness itself , is not the result of a a concatenation of essential and inessential anatomical parts. The lungs, heart and all other organs make no sense understood in isolation from the functioning of the organism as a whole to which they contribute. Certainly you can eliminate subprocesses or individual organs. Depending on their contribution to the total functioning of the body-mind-environment system their absence will have a minor or or major effect on the whole functioning , including consciousness. We can remove a lung or a kidney with only minor impact, but not both without replacing their function somehow. We can destroy individual neurons with imperceptible effect, but with enough destruction eventually the impact will be significant. Notice that when damage to any organ is severe enough, the effects on the body are systematic, potentially affecting metabolism, concentration, appetite , balance, etc, since these are intercorrelated. That’s because the function of every organ system takes into account every other aspect of the organism’s functioning, and is designed for the sake of the whole.
. In theory , a biologist could deduce all of the functional properties of an organism from just its heart or liver, such as the size of the animal, it’s environment , diet, form of mobility, etc. But the part would only tell you all this if you already knew the relationship between it and all of these other aspects of an animal’s body-environment functioning, that it is a functioning whole that we can artificially separate into parts ina second step , rather than it being an assembly of parts that exist as parts first and only later belong to the totality. We can treat machines this way , like an auto engine , but even here, we didn’t begin with isolated parts later brought together. The original conception began from a functional whole and derived the parts from
I’m not arguing that the organism is an undifferentiated whole. Of course there are differentiated subsystems. The brain cannot pump the blood , the lungs cant think, the liver cannot hear. But alterations to any of these processes ( circulatory blockage, liver toxicity , renal failure, copd, Alzheimer’s) changes the functioning of all the other processes in some fashion, including consciousness.
As far as the brain not being able to feel itself , the sensations from the receptors cannot be consciously felt in isolation from other brain contributions no matter how healthy they are , because conscious feeling is not simply receptor stimulation but a complex
, differentiated process of perception, most of which takes place far away from the sensory source. This is also the reason for phantom limb syndrome , the real feeling of sensation arising from an amputated limb. The receptors are no longer three , but the brain processes of sensory perception are still active.
In sum, we can’t treat organ systems and other subprocesses of the body as interchangeable , but neither can we understand what they are in themselves without understanding what they do, and we cannot understand what they do without knowing how they interact in reciprocal fashion with all other systems of the body for the sake of a total functionally unified system. And this total body system cannot be understood without knowing how it forms a body-environment process. You remove the environment for which it was designed and is continually being shaped and you fail to understand the body.