Re: Why does it take 20 min. for your stomach to signal your brain you're full?

Right, why does it take so long?  The hypothalamus--located in the central 
portion of your brain--has areas that regulate many basic systems.  It has 
centers for appetite as well as for thirst.  When you eat, your stomach 
will send signals to the brain through the vagus nerve.  This is a 
complicated pathway.  This will generate some delay.  The hypothalamus 
will have to recognize the signal then trigger its centers to recognize 
the degree of "fullness."


The pathways are very complicated and involve multiple areas of the 
brain.  For example, you are not conscious of the workings of the 
hypothalamus; these singals and responses have to eventually reach 
consciousness.  This will create a delay.


If you need to know the actual hypothalamic areas and the complicated 
pathways, I would start with a basic physiology text:


Review of Medical Physiology, William F. Ganong, McGraw-Hill 
Professional Publishing; ISBN: 0838582826; 20th edition (March 5, 2001) 


This can then direct to the more complicated texts.  Another good start is:


Nervous System : Neurologic and Neuromuscular Disorders (Ciba 
Collection of Medical Illustrations, Vol 1), Frank Netter, Novartis 
Medical Education; ISBN: 0914168118; (February 1986) 


--Doctor X