How is the stomach involved in the circulatory and nervous systems?
The stomach provides the energy needed for both systems
The stomach itself is a part of the digestive system , and isn't a part of the circulatory or nervous system . It does play a vital role, however, as it produces the nutrients necessary for these systems to function. Without the digestive system, there would be no energy to circulate blood around the body, nor would there be energy for the transmission of messages across nevre cells and neurons. On the other hand, without the circulatory system circulating oxygen, the stomach cells wouldn't be able to function, so their processes are codependent.
This isn't true for the nervous system and stomach though. Research has shown that although the autonomic nervous system and enteric nervous system (nervous system around the gut) do communicate thorugh the vagus nerve, when the vagus nerve is cut the enteric nervous system continues to function. Because of this, the nervous system around the stomach has been described as "a second brain," so technically the nervous system needs the stomach more than the stomach needs the nervous system.
I hope I helped!