CHAPTER XLV 



Central control of digestive function 



SVEN G. ELIASSON 



Department of Internal Medicine, The University nf Texas Southwestern 

 Medical School, Dallas, Texas 



CHAPTER C C) N T E N T S 



Role of the Central Neisous System in Digestive Function 



Comparative Physiology 



Mastication 



Swallowing 



Gastrointestinal Motility 



Vomiting 



Gastric Secretion 



Emotional Influence on Digestive Function 



ROLE OF THE CENTRAL NERVOUS SYSTEM 

 IN DIGESTIVE FUNCTION 



THE MAIN FUNCTIONS of the digestive system are 

 mechanical and chemical subdivision of the ingested 

 material, transportation, absorption and excretion. 

 These functions present no problem in the one-celled 

 animal but become increasingly complex at the 

 higher developmental stages. The increase in size of 

 the animal and the introduction of regions with spe- 

 cialized functions in the digestive systein parallels 

 the development of local nervous mechanisms with 

 regulatory functions. These consist of groups of nerve 

 cells which coordinate activity in neighboring regions 

 of the alimentary canal. These cells presumably also 

 receive impulses from receptors in the wall of the 

 intestine. When a central nervous system is de- 

 \eloped, some of the information about the state of 

 the digestive system is transmitted to the brain. In 

 the brain the information is correlated with informa- 

 tion received from other .sources which have direct 

 or indirect influence on the digestive functions. The 

 integrated response is relayed to the local regulatory 

 mechanism or directlv to the effector organs. Thus 



the central nervous system exerts partial control o\er 

 the activity in the digestive system. 



The pertinent questions regarding the relationship 

 between the central nervous system and the digestive 

 system are, first, to what extent does the central nerv- 

 ous system participate in normal digestive function? 

 And second, to what extent do pathological changes 

 in one system affect the other? An attempt to provide 

 an answer to these questions must take into considera- 

 tion the fact that different animals may have found 

 different solutions to the same problems. The primary 

 requirement that nutritional substances of the right 

 consistency and in the correct amount are distributed 

 over a surface suitable for absorption must be met. 

 (The control of food intake by hunger and appetite 

 is considered in Chapter XLVII of this Handbook 

 by Brobeck.) In animals with .similar anatomical 

 structure and nearly identical requirements, the 

 relative importance of central and peripheral factors 

 may still vary. 



It is theoretically possible to reach an answer to 

 the simple question of the importance of the central 

 nervous system for digestion (or for any other func- 

 tion) simply by removing as much of it as possible. 

 Such an experiment can definitely give us information 

 as to whether the organism can or cannot perform 

 digestive functions after the procedure. It does not 

 give any information about the normal participation 

 of the central nervous system in digestive function. 

 Removal of small localized regions of the brain or 

 cord may cause a change in the output to the digestive 

 system whether the removed region was a part of the 

 central control system for digestive function or not. 



Electrical stimulation of various regions of the brain 

 will cause changes in the activity of the gastrointes- 

 tinal canal. These regions then have access to path- 



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