Individual differences |
Methods | Statistics | Clinical | Educational | Industrial | Professional items | World psychology |
Biological: Behavioural genetics · Evolutionary psychology · Neuroanatomy · Neurochemistry · Neuroendocrinology · Neuroscience · Psychoneuroimmunology · Physiological Psychology · Psychopharmacology (Index, Outline)
- Main article: Psychology and digestion
- Main article: Effects of stress on digestion
Digestion is the process of metabolism undertaken in the digestive system where an organism processes a substance in order to chemically and mechanically convert the substance for the body to use. Preparation for digestion follows ingestion and begins with the cephalic phase producing saliva and enzyme production. Mechanical and chemical digestion occur in the mouth and stomach; food is chewed, and mixed with saliva in the mouth, and further broken down through mechanical and chemical processing in the stomach having been swallowed. Absorbtion occurs in the stomach and gastrointestinal tract, and the process finishes with excretion.
Digestion occurs at the multicellular, cellular, and sub-cellular levels, usually in animals. This process takes place in the digestive system, gastrointestinal tract, or alimentary canal. The digestive system as a whole is a one-way tube with accessory organs like the liver, gallbladder, and pancreas adding substances to the process of digestion.
Digestion is usually divided into mechanical manipulation and chemical action. In most vertebrates, digestion is a multi-stage process in the digestive system, following ingestion of the raw materials, most often other organisms. The process of ingestion usually involves some type of mechanical manipulation. Digestion is separated into four separate processes:
- Ingestion: placing food into the mouth,
- Mechanical digestion & chemical digestion: mastication, the use of teeth to tear and crush food, and churning of the stomach. Addition of chemicals (acid, bile, enzymes, and water) to break down complex molecules into simple structures,
- Absorption: movement of nutrients from the digestive system to the circulatory and lymphatic capillaries through osmosis, active transport, and diffusion,
- Egestion: Removal of undigested materials from the digestive tract through defecation.
Human digestion processEdit
Phases of human digestionEdit
- Cephalic phase - This phase occurs before food enters the stomach and involves preparation of the body for eating and digestion. Sight and thought stimulate the cerebral cortex. Taste and smell stimulus is sent to the hypothalamus and medulla oblongata. After this it is routed through the vagus nerve.
- Gastric phase - This phase takes 3 to 4 hours. It is stimulated by distention of the stomach and alkaline pH. Distention activates long and myentric reflexes. This activates the release of acetylcholine which stimulates the release of more gastric juices. As protein enters the stomach, it binds to hydrogen ions, which raises the pH of the stomach to an alkaline level. This triggers G cells to release gastrin, which in turn stimulates parietal cells to secrete HCl. HCl release is also triggered by acetylcholine and histamine.
- Intestinal phase - This phase has 2 parts, the excitatory and the inhibitory. Partially-digested food fills the duodenum. This triggers intestinal gastrin to be released. Enterogastric reflex inhibits vagal nuclei, activating sympathetic fibers causing the pyloric sphincter to tighten to prevent more food from entering, and inhibits local reflexes.
- Main article: Mouth (human)
In humans, digestion begins in the oral cavity where food is chewed. Saliva is secreted in large amounts (1-1.5 litre/day) by three pairs of exocrine salivary glands (parotid, submandibular, and sublingual) in the oral cavity, and is mixed with the chewed food by the tongue. There are two types of saliva. One is a thin, watery secretion, and its purpose is to wet the food. The other is a thick, mucous secretion, and it acts as a lubricant and causes food particles to stick together and form a bolus. The saliva serves to clean the oral cavity and moisten the food, and contains digestive enzymes such as salivary amylase, which aids in the chemical breakdown of polysaccharides such as starch into disaccharides such as maltose. It also contains mucin, a glycoprotein which help soften the food into a bolus.
Swallowing transports the chewed food into the esophagus, passing through the oropharynx and hypopharynx. The mechanism for swallowing is coordinated by the swallowing center in the medulla oblongata and pons. The reflex is initiated by touch receptors in the pharynx as the bolus of food is pushed to the back of the mouth.
- Main article: Esophagus
The esophagus, a narrow, muscular tube about 20 centimeters (8 inches) long, starts at the pharynx, passes through the thorax and diaphragm, and ends at the cardiac orifice of the stomach. The wall of the esophagus is made up of two layers of smooth muscles, which form a continuous layer from the esophagus to the rectum and contract slowly, over long periods of time. The inner layer of muscles is arranged circularly in a series of descending rings, while the outer layer is arranged longitudinally. At the top of the esophagus, is a flap of tissue called the epiglottis that closes during swallowing to prevent food from entering the trachea (windpipe). The chewed food is pushed down the esophagus to the stomach through peristaltic contraction of these muscles. It takes only seconds for food to pass through the esophagus, and little digestion actually takes place.
- Main article: Stomach
The food enters the stomach after passing through the cardiac orifice. In the stomach, food is further broken apart thoroughly mixed with a gastric acid and digestive enzymes that break down proteins. The acid itself does not break down food molecules, rather, the acid provides an optimum pH for the reaction of the enzyme pepsin. The parietal cells of the stomach also secrete a glycoprotein called intrinsic factor which enables the absorption of vitamin B-12. Other small molecules such as alcohol are absorbed in the stomach as well by passing through the membrane of the stomach and entering the circulatory system directly.
- Main article: Small intestine
After being processed in the stomach, food is passed to the small intestine via the pyloric sphincter. The majority of digestion and absorption occur here as chyme enters the duodenum. Here it is further mixed with three different liquids:
- bile, which emulsifies fats to allow absorption, neutralizes the chyme, and is used to excrete waste products such as bilin and bile acids (which has other uses as well). However, it is not an enzyme!
- pancreatic juice made by the pancreas
- intestinal enzymes of the alkaline mucosal membranes. The enzymes include: maltase, lactase and sucrase, to process sugars; trypsin and chymotrypsin are also added in the small intestine
Most nutrient absorption takes place in the small intestine. As the acid level changes in the small intestines, more enzymes are activated to split apart the molecular structure of the various nutrients so they may be absorbed into the circulatory or lymphatic systems. Nutrients pass through the small intestine's wall, which contains small, finger-like structures called villi(singular villus), and each villus contains even smaller hair-like structures called microvilli. The blood, which has absorbed nutrients, is carried away from the small intestine via the hepatic portal vein and goes to the liver for filtering, removal of toxins, and nutrient processing.
The small intestine and remainder of the digestive tract undergoes peristalsis to transport food from the stomach to the rectum and allow food to be mixed with the digestive juices and absorbed. The circular muscles and longitudinal muscles are antagonistic muscles, with one contracting as the other relaxes. When the circular muscles contract, the lumen becomes narrower and longer and the food is squeezed and pushed forward. When the longitudinal muscles contract, the circular muscles relax and the gut dilates to become wider and shorter to allow food to enter.
- Main article: Large intestine
After the food has been passed through the small intestine, the food enters the large intestine. The large intestine is roughly 1.5 meters long, with three parts: the cecum at the junction with the small intestine, the colon, and the rectum. The colon itself has four parts: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. The large intestine absorbs water from the bolus and stores feces until it can be excreted. Food products that cannot go through the villi, such as cellulose (dietary fiber), are mixed with other waste products from the body and become feces.
Carbohydrates are formed in growing plants and are found in grains, leafy vegetables, and other edible plant foods. The molecular structure of these plants is complex, or a polysaccharide; poly is a prefix meaning many. Plants form carbohydrate chains during growth by trapping carbon from the atmosphere, initially carbon dioxide (CO2). Carbon is stored within the plant along with water (H2O) to form a complex starch containing a combination of carbon-hydrogen-oxygen in a fixed ratio of 1:2:1 respectively.
Plants with a high sugar content and table sugar represent a less complex structure and are called disaccharides, or two sugar molecules bonded. Once digestion of either of these forms of carbohydrates are complete, the result is a single sugar structure, a monosaccharide. These monosaccharides can be absorbed into the blood and used by individual cells to produce the energy compound adenosine triphosphate (ATP).
The digestive system starts the process of breaking down polysaccharides in the mouth through the introduction of amylase, a digestive enzyme in saliva. The high acid content of the stomach inhibits the enzyme activity, so carbohydrate digestion is suspended in the stomach. Upon emptying into the small intestines, potential hydrogen (pH) changes dramatically from a strong acid to an alkaline content. The pancreas secretes bicarbonate to neutralize the acid from the stomach, and the mucus secreted in the tissue lining the intestines is alkaline which promotes digestive enzyme activity. Amylase is present in the small intestines and works with other enzymes to complete the breakdown of carbohydrate into a monosaccharide which is absorbed into the surrounding capillaries of the villi.
Nutrients in the blood are transported to the liver via the hepatic portal circuit, or loop, where final carbohydrate digestion is accomplished in the liver. The liver accomplishes carbohydrate digestion in response to the hormones insulin and glucagon. As blood glucose levels increase following digestion of a meal, the pancreas secretes insulin causing the liver to transform glucose to glycogen, which is stored in the liver, adipose tissue, and in muscle cells, preventing hyperglycemia. A few hours following a meal, blood glucose will drop due to muscle activity, and the pancreas will now secrete glucagon which causes glycogen to be converted into glucose to prevent hypoglycemia.
Note: In the discussion of digestion of carbohydrates; nouns ending in the suffix -ose usually indicate a sugar, such as lactose. Nouns ending in the suffix -ase indicates the enzyme that will break down the sugar, such as lactase. Enzymes usually begin with the substrate (substance) they are breaking down. For example: maltose, a disaccharide, is broken down by the enzyme maltase (by the process of hydrolysis), resulting in a two glucose molecules, a monosaccharide.
The presence of fat in the small intestine produces hormones which stimulate the release of lipase from the pancreas and bile from the gallbladder. The lipase (activated by acid) breaks down the fat into monoglycerides and fatty acids. The bile emulsifies the fatty acids so they may be easily absorbed.
Short- and medium chain fatty acids are absorbed directly into the blood via intestine capillaries and travel through the portal vein just as other absorbed nutrients do. However, long chain fatty acids are too large to be directly released into the tiny intestine capillaries. Instead they are absorbed into the fatty walls of the intestine villi and reassembled again into triglycerides. The triglycerides are coated with cholesterol and protein (protein coat) into a compound called a chylomicron.
Within the villi, the chylomicron enters a lymphatic capillary called a lacteal, which merges into larger lymphatic vessels. It is transported via the lymphatic system and the thoracic duct up to a location near the heart (where the arteries and veins are larger). The thoracic duct empties the chylomicrons into the bloodstream via the left subclavian vein. At this point the chylomicrons can transport the triglycerides to where they are needed.
There are at least four hormones that aid and regulate the digestive system:
- Gastrin - is in the stomach and stimulates the gastric glands to secrete pepsinogen(an inactive form of the enzyme pepsin) and hydrochloric acid. Secretion of gastrin is stimulated by food arriving in stomach. The secretion is inhibited by low pH .
- Secretin - is in the duodenum and signals the secretion of sodium bicarbonate in the pancreas and it stimulates the bile secretion in the liver. This hormone responds to the acidity of the chyme.
- Cholecystokinin (CCK) - is in the duodenum and stimulates the release of digestive enzymes in the pancreas and stimulates the emptying of bile in the gall bladder. This hormone is secreted in response to fat in chyme.
- Gastric inhibitory peptide (GIP) - is in the duodenum and decreases the stomach churning in turn slowing the emptying in the stomach. Also functions is to induce insulin secretion
Significance of pH in digestionEdit
Digestion is a complex process which is controlled by several factors. pH plays a crucial role in a normally functioning digestive tract. In the mouth, pharynx, and esophagus, pH is typically about 6.8, very weakly acidic. Saliva controls pH in this region of the digestive tract. Salivary amylase is contained in saliva and starts the breakdown of carbohydrates into monosaccharides. Most digestive enzymes are sensitive to pH and will not function in a low-pH environment like the stomach. Low pH (below 5) indicates a strong acid, while a high pH (above 8) indicates a strong base; the concentration of the acid or base, however, does also play a role.
pH in the stomach is very acidic and inhibits the breakdown of carbohydrates while there. The strong acid content of the stomach provides two benefits, both serving to denature proteins for further digestion in the small intestines, as well as providing non-specific immunity, retarding or eliminating various pathogens.
In the small intestines, the duodenum provides critical pH balancing to activate digestive enzymes. The liver secretes bile into the duodenum to neutralise the acidic conditions from the stomach. Also the pancreatic duct empties into the duodenum, adding bicarbonate to neutralize the acidic chyme, thus creating a neutral environment. The mucosal tissue of the small intestines is alkaline, creating a pH of about 8.5, thus enabling absorption in a mild alkaline in the environment.
Specialized organs in non-human animalsEdit
Organisms have evolved specialized organs to aid in the digestion of their food, modifying tongues, teeth and other organs to assist in digestion. Certain insects may have a crop or enlarged esophagus while birds and cockroaches developed gizzards to assist in the digestion of tough materials. Herbivore evolved cecums (or a abomasum in the case of ruminants) to break down cellulose in plants.
- Ackroff, K., & Sclafani, A. (1991). Sucrose to Polycose preference shifts in rats: The role of taste, osmolality and the fructose moiety: Physiology & Behavior Vol 49(6) Jun 1991, 1047-1060.
- Baer, D. J., Oftedal, O. T., & Fahey, G. C. (1985). Feed selection and digestibility by captive giraffe: Zoo Biology Vol 4(1) 1985, 57-64.
- Baldaro, B., Battacchi, M. W., Trombini, G., Palomba, D., & et al. (1990). Effects of an emotional negative stimulus on the cardiac, electrogastrographic and respiratory responses: Perceptual and Motor Skills Vol 71(2) Oct 1990, 647-655.
- Baldaro, B., Gattacchi, M. W., Codispoti, M., & Tuozzi, G. (1996). Modification of electrogastrographic activity during the viewing of brief film sequences: Perceptual and Motor Skills Vol 82(3, Pt 2) Jun 1996, 1243-1250.
- Berger, K., Winzell, M. S., Mei, J., & Erlanson-Albertsson, C. (2004). Enterostatin and its target mechanisms during regulation of fat intake: Physiology & Behavior Vol 83(4) Dec 2004, 623-630.
- Bernardis, L. L., & Bellinger, L. L. (1982). Effect of diet hydration on food and water intake, efficiency of food utilization and response to fast and realimentation in rats with dorsomedial hypothalamic hypophagia and growth retardation: Appetite Vol 3(1) Mar 1982, 35-52.
- Blinder, B. J., & Hagman, J. (1986). Serum salivary isoamylase levels in patients with anorexia nervosa, bulimia or bulimia nervosa: Hillside Journal of Clinical Psychiatry Vol 8(2) Fal-Win 1986, 152-163.
- Booth, D. A., Stoloff, R., & Nicholls, J. (1974). Dietary flavor acceptance in infant rats established by association with effects of nutrient composition: Physiological Psychology Vol 2(3-A) Sep 1974, 313-319.
- Bueno, L., Fargeas, M. J., & Julie, P. (1986). Effects of calcitonin and CGRP alone or in combination on food intake and forestomach (reticulum) motility in sheep: Physiology & Behavior Vol 36(5) 1986, 907-911.
- Callahan, J. B., & Rinaman, L. (1998). The postnatal emergence of dehydration anorexia in rats is temporally associated with the emergence of dehydration-induced inhibition of gastric emptying: Physiology & Behavior Vol 64(5) Jul 1998, 683-687.
- Chauhan, V., Sheikh, A. M., Chauhan, A., Spivack, W. D., Fenko, M. D., & Malik, M. N. (2005). Fibrillar amyloid beta-protein inhibits the activity of high molecular weight brain protease and trypsin: Journal of Alzheimer's Disease Vol 7(1) 2005, 37-44.
- Chernigovsky, V. N., Talan, M. I., Polyakov, E. L., & Knyaz'kova, S. (1978). Hypothalamic self-stimulation and duodenum motor activity: Physiology & Behavior Vol 21(1) Jul 1978, 1-5.
- Conover, K. L., Collins, S. M., & Weingarten, H. P. (1989). Pyloroplasty does not disrupt liquid phase gastric emptying or CCK-induced satiety: Physiology & Behavior Vol 45(3) Mar 1989, 523-528.
- Conover, K. L., Weingarten, H. P., & Collins, S. M. (1987). A procedure for within-trial repeated measurement of gastric emptying in the rat: Physiology & Behavior Vol 39(3) 1987, 303-308.
- Corbett, S. W., & Keesey, R. E. (1980). Digestibility in male rats with lateral hypothalamic lesions: Physiology & Behavior Vol 24(6) Jun 1980, 1165-1168.
- Demetrio, F. N., Soares, M. N. d. T., Moreno, R. A., Aguirre Costa, P. L., Lopasso, F. P., & Laudanna, A. A. (1999). Treatment of depression effect on gastric emptying: Revista Brasileira de Psiquiatria Vol 21(1) Jan-Mar 1999, 6-11.
- Deutsch, J. A., Puerto, A., & Wang, M.-l. (1977). The pyloric sphincter and differential food preference: Behavioral & Neural Biology Vol 19(4) Apr 1977, 543-547.
- DiBattista, D. (1984). Effects of 5-thio-D-glucose and 2-deoxy-D-glucose upon stomach-emptying in the golden hamster: Physiology & Behavior Vol 33(4) Oct 1984, 543-545.
- DiBattista, D. (1991). Lactose ingestion in the adult golden hamster (Mesocricetus auratus): Journal of Comparative Psychology Vol 105(1) Mar 1991, 95-102.
- Dubois, A., & Natelson, B. H. (1978). Habituation of gastric function suppression in monkeys after repeated free-operant avoidance sessions: Physiological Psychology Vol 6(4) Dec 1978, 524-528.
- Duggan, J. P., & Booth, D. A. (1986). Obesity, overeating, and rapid gastric emptying in rats with ventromedial hypothalamic lesions: Science Vol 231(4738) Feb 1986, 609-611.
- Engstrom, R., & Deaux, E. (1974). Stomach distention as a regulation of fluid intake: Physiological Psychology Vol 2(3-A) Sep 1974, 337-340.
- Ferrando, R., Garrigues, T. M., Bermejo, M. V., Martin-Algarra, R., Merino, V., & Polache, A. (1999). Effects on ethanol on intestinal absorption of drugs: In situ studies with ciprofloxacin analogs in acute and chronic alcohol-fed rats: Alcoholism: Clinical and Experimental Research Vol 23(8) Aug 1999, 1403-1408.
- Frith, C. K., Buffalo, M. D., & Montague, J. C. (1985). Reported dietary effects on esophageal voice production: Folia Phoniatrica Vol 37(5-6) Sep-Dec 1985, 238-245.
- Fulgoni, V. L. (1984). The relationship of body size, lactation or gestation with ration intake, nutrient digestibility and digestible nutrient intake in beef cattle: Dissertation Abstracts International.
- Garcia, J., Hankins, W. G., Robinson, J. H., & Vogt, J. L. (1972). Bait shyness: Tests of CS-US mediation: Physiology & Behavior Vol 8(5) May 1972, 807-810.
- Giguere, L. A. (1982). The energetics of predation: A components study of Chaoborus trivittatus larvae: Dissertation Abstracts International.
- Guignard, F. (1995). Pregenitality and the primal scene, or the fantasy destiny of the digestive tract: Revue Francaise de Psychanalyse Vol 59(3) Jul-Sep 1995, 771-784.
- Guillemette, M. (1994). Digestive-rate constraint in wintering common eiders (Somateria mollissima): Implications for flying capabilities: Auk Vol 111(4) Oct 1994, 900-909.
- Gusca, N. I., Sheptitsky, V. A., & Razlovan, T. A. (1993). The role of dopamine in the regulatory mechanism of digestive-transporting functions of the enterocytes' membrane under stress: Fiziologicheskii Zhurnal SSSR im I M Sechenova Vol 79(6) Jun 1993, 40-47.
- Harris, M. E. (1977). Symptom-related differences in the biofeedback performances of psychosomatic patients: Dissertation Abstracts International.
- Hatt, J.-M., Lechner-Doll, M., & Mayes, B. (1998). The use of dosed and herbage n-alkanes as markers for the determination of digestive strategies of captive giraffes (Giraffa camelopardalis): Zoo Biology Vol 17(4) 1998, 295-309.
- Hiji, Y. (1975). Selective elimination of taste responses to sugars by proteolytic enzymes: Nature Vol 256(5516) Jul 1975, 427-429.
- Hirota, N., Sone, Y., & Tokura, H. (2003). Effect of evening exposure to dim or bright light on the digestion of carbohydrate in the supper meal: Chronobiology International Vol 20(5) 2003, 853-862.
- Holifield, R. D. (1990). The effect of visual food cues on gastric motility: Dissertation Abstracts International.
- Holt, S., Ford, M. J., Grant, S., & Heading, R. C. (1981). Abnormal gastric emptying in primary anorexia nervosa: British Journal of Psychiatry Vol 139 Dec 1981, 550-552.
- Holt, S. H. A., & Miller, J. B. (1995). Increased insulin responses to ingested foods are associated with lessened satiety: Appetite Vol 24(1) Feb 1995, 43-54.
- Hossain, S., Alim, A., Takeda, K., Kaji, H., Shinoda, T., & Ueda, K. (2001). Limited proteolysis of NACP/alpha -synuclein: Journal of Alzheimer's Disease Vol 3(6) 2001, 577-584.
- Houpt, K. A., & Houpt, T. R. (1979). Gastric emptying and cholecystokinin in the control of food intake in suckling rats: Physiology & Behavior Vol 23(5) Nov 1979, 925-929.
- Krakovsky, M. E., Lisenko, T. E., & Komarin, A. S. (1989). Emotional behaviour and the interrelationship between the processes of the membrane and cavity digestion: Fiziologicheskii Zhurnal SSSR im I M Sechenova Vol 75(6) Jun 1989, 824-828.
- Laurila, M., Hohtola, E., Saarela, S., & Rashotte, M. E. (2003). Adaptive timing of digestion and digestion-related thermogenesis in the pigeon: Physiology & Behavior Vol 78(3) Mar 2003, 441-448.
- Leon-Sanchez, R., Palafox, G. P., & Garcia, K. B. (2005). Children's ideas about the digestive process: Revista Mexicana de Psicologia Vol 22(1) Jun 2005, 137-158.
- Liu, Y. (2005). Pavlov's view on organism and environment: True or false? : Australian and New Zealand Journal of Psychiatry Vol 39(8) Aug 2005, 737-738.
- Maddison, S. (1978). Predigestion and suppression of food intake by gastric loads: Physiology & Behavior Vol 21(4) Oct 1978, 497-501.
- Malbert, C. H., & Ruckebusch, Y. (1989). Hyperphagia induced by pylorectomy in sheep: Physiology & Behavior Vol 45(3) Mar 1989, 495-499.
- Manfredi, E., Bassa Poropat, M. T., Trevisan, M., & Levi, N. (1986). Massive intestinal atresia: A case of digestive rehabilitation: Eta Evolutiva No 24 Jun 1986, 23-33.
- Marks, I. M. (2004). The Nobel prize award in physiology to Ivan Petrovich Pavlov - 1904: Australian and New Zealand Journal of Psychiatry Vol 38(9) Sep 2004, 674-677.
- Mei, J., Lindqvist, A., Krabisch, L., Rehfeld, J. F., & Erlanson-Albertsson, C. (2006). Appetite suppression through delayed fat digestion: Physiology & Behavior Vol 89(4) Nov 2006, 563-568.
- Mela, D. J. (2006). Novel Food Technologies: Enhancing Appetite Control in Liquid Meal Replacers: Obesity Vol 14(Suppl 4) Jul 2006, 179S-181S.
- Mitsui, T., Kagami, H., Kinomoto, H., Ito, A., Kondo, T., & Shimaoka, K. (2003). Small bowel bacterial overgrowth and rice malabsorption in healthy and physically disabled older adults: Journal of Human Nutrition and Dietetics Vol 16(2) Apr 2003, 119-122.
- Molina, F., Thiel, T., Deutsch, J. A., & Puerto, A. (1977). Comparison between some digestive processes after eating and gastric loading in rats: Pharmacology, Biochemistry and Behavior Vol 7(4) Oct 1977, 347-350.
- Moos, A. B., McLaughlin, C. L., & Baile, C. A. (1982). Effects of CCK on gastrointestinal function in lean and obese Zucker rats: Peptides Vol 3(4) Jul-Aug 1982, 619-622.
- Morse, D. R., & et al. (1985). The effects of stress and relaxation on oral digestion of a complex carbohydrate food: International Journal of Psychosomatics Vol 32(3) 1985, 20-27.
- Newman, J. C., & Booth, D. A. (1981). Gastrointestinal and metabolic consequences of a rat's meal on maintenance diet ad libitum: Physiology & Behavior Vol 27(5) Nov 1981, 929-939.
- Palmer, R. E. (1980). Behavioral and rhythmic aspects of feeding and digestion in the baby scallop Argopecten irradians and the oyster Crassostrea virginica: Dissertation Abstracts International.
- Phillips, D. J. (1995). Relationship between challenge-induced physiological responses and postprandial gastrin release in normal, healthy males. Dissertation Abstracts International: Section B: The Sciences and Engineering.
- Powley, T. L. (1977). The ventromedial hypothalamic syndrome, satiety, and a cephalic phase hypothesis: Psychological Review Vol 84(1) Jan 1977, 89-126.
- Rabe, E. F., & Corbit, J. D. (1973). Postingestional control of sodium chloride solution drinking in the rat: Journal of Comparative and Physiological Psychology Vol 84(2) Aug 1973, 268-274.
- Ralph, T. L., & Sawchenko, P. E. (1978). Differential effects of lateral and ventromedial hypothalamic lesions on gastrointestinal transit in the rat: Brain Research Bulletin Vol 3(1) Jan-Feb 1978, 11-14.
- Rashotte, M. E., Phillips, D. L., & Henderson, R. P. (1997). Nocturnal digestion, cloacal excretion, and digestion-related thermogenesis in pigeons (Columba livia): Physiology & Behavior Vol 61(1) Jan 1997, 83-92.
- Rast, J. T. (1985). Effects of oropharyngeal and esophageal stimuli on ruminative behavior: Dissertation Abstracts International.
- Robinson, P. H., & Stephenson, J. S. (1990). Dietary restriction delays gastric emptying in rats: Appetite Vol 14(3) Jun 1990, 193-201.
- Robinson, T. M., Abbott, P., & Kristal, M. B. (1995). Blockade of digestion by famotidine pretreatment does not interfere with the opioid-enhancing effect of ingested amniotic fluid: Physiology & Behavior Vol 57(2) Feb 1995, 261-263.
- Rogers, R. C., McTigue, D. M., & Hermann, G. E. (1996). Vagal control of digestion: Modulation by central neural and peripheral endocrine factors: Neuroscience & Biobehavioral Reviews Vol 20(1) Spr 1996, 57-66.
- Rowland, N. E., & Carlton, J. (1984). Inhibition of gastric emptying by peripheral and central fenfluramine in rats: Correlation with anorexia: Life Sciences Vol 34(25) Jun 1984, 2495-2499.
- Rowland, N. E., & Carlton, J. (1986). Tolerance to fenfluramine anorexia: Fact or fiction? : Appetite Vol 7(Suppl) 1986, 71-83.
- Ruckebusch, Y., & Malbert, C. H. (1986). Stimulation and inhibition of food intake in sheep by centrally-administered hypothalamic releasing factors: Life Sciences Vol 38(10) Mar 1986, 929-934.
- Savory, C. J. (1986). Influence of ambient temperature on feeding activity parameters and digestive function in domestic fowls: Physiology & Behavior Vol 38(3) 1986, 353-357.
- Savory, C. J., & Hodgkiss, J. P. (1984). Influence of vagotomy in domestic fowls on feeding activity, food passage, digestibility and satiety effects of two peptides: Physiology & Behavior Vol 33(6) Dec 1984, 937-944.
- Sibbald, A. M., Shellard, L. J. F., & Smart, T. S. (2000). Effects of space allowance on the grazing behaviour and spacing of sheep: Applied Animal Behaviour Science Vol 70(1) Nov 2000, 49-62.
- Smith, G. P. (1998). Satiation: From gut to brain. New York, NY: Oxford University Press.
- Smith, G. P., & Gibbs, J. (1976). What the gut tells the brain about feeding behavior. Oxford, England: Abakon Verlagsgesellschaft.
- Steele, T. L. (1986). Temperature-dependent drinking in rats with septal lesions: Dissertation Abstracts International.
- Swithers, S. E. (2000). Effects of metabolic inhibitors on ingestive behavior and physiology in preweanling rat pups: Appetite Vol 35(1) Aug 2000, 9-25.
- Toyama, N. (2000). "What are food and air like inside our bodies?": Children's thinking about digestion and respiration: International Journal of Behavioral Development Vol 24(2) Jun 2000, 222-230.
- Vachon, C., & Savoie, L. (1987). Circadian variation of food intake and digestive tract contents in the rat: Physiology & Behavior Vol 39(5) 1987, 629-632.
- Van Soest, P. J. (1996). Allometry and ecology of feeding behavior and digestive capacity in herbivores: A review: Zoo Biology Vol 15(5) 1996, 455-479.
- Wayner, M., & Carey, R. J. (1973). Basic drives: Annual Review of Psychology 1973, 53-80.
- Weller, A., & Tsitolovskya, L. (2004). The ontogeny of the postingestive inhibitory effect of peptone in rats: Physiology & Behavior Vol 82(1) Aug 2004, 11-16.
- Wiepkema, P. R., Alingh Prins, A. J., & Steffens, A. B. (1972). Gastrointestinal food transport in relation to meal occurrence in rats: Physiology & Behavior Vol 9(5) Nov 1972, 759-763.
- Williams, T. A. (1909). Mental causes in bodily disease: The most frequent cause of the origins of "nervous Indigestion." The Journal of Abnormal Psychology Vol 3(6) Feb-Mar 1909, 386-390.
- Windholz, G. (2000). Pavlov, Ivan Petrovich: Kazdin, Alan E (Ed).
- Wyrwicka, W. (1979). Changes in gastric acid secretion in aphagic or hyperphagic cats after hypothalamic lesions: Experimental Neurology Vol 63(2) Feb 1979, 293-303.
- Young, W. G., & Deutsch, J. A. (1980). Intragastric pressure and receptive relaxation in the rat: Physiology & Behavior Vol 25(6) Dec 1980, 973-975.
- Kimball's Biology Pages, Digestion
- Chemistry lecture
- American Journal of Physiology, article
- Journal article on pH in digestion
- Human Physiology - Digestion
- NIH guide to digestive system
|This page uses Creative Commons Licensed content from Wikipedia (view authors).|