Most of our abdominal organs, also called abdominal viscera, are a part of the digestive system. These include the stomach, the small and large intestine, the liver, gallbladder and pancreas.
The abdomen is also home to other organs, like the spleen, kidneys, suprarenal glands, and the ureters, which play important roles in other systems.
All of these organs work involuntarily, so they’re innervated by the autonomic nervous system. And luckily so - can you imagine trying to voluntarily control digesting each vegetable in a salad?!
Ok, now remember that our nervous system is divided into the central nervous system and the peripheral nervous system.
Functionally, the peripheral nervous system is also divided into two parts. The somatic nervous system controlling the voluntary movement of skeletal muscles, and the autonomic nervous system that controls the involuntary movement of the smooth muscles and also the glands of our organs or viscera.
Now, the autonomic nervous system is also divided into two parts; the sympathetic, and parasympathetic nervous systems.
The sympathetic nervous system is our fight or flight response and increases heart rate and breathing rate, while slowing down digestion through reducing peristalsis and constricting blood vessels to the gut to reduce blood flow.
The parasympathetic nervous system is our rest and digest response and it slows down heart rate, and increases digestion by promoting peristalsis, gland secretion, and dilation of gut vessels for increased blood flow.