Homeostasis & The Digestive System

1. Hungry??? Homeostasis &The Digestive System

2. Nutritional requirements • Animals are heterotrophs • need to take in food • Why? fulfills 3 needs… • fuel = chemical energy for production of ATP • raw materials = carbon sources for biosynthesis • essential nutrients = substances animals cannot make themselves • elements (N, P, K, Fe, Na, K, Ca, etc.), NAD, FAD, etc.

3. Energy budget { • basal (resting) metabolism • activity • temperature regulation food intake ATPproduction { • growth • reproduction biosynthesis { • glycogen • fat storage

4. A body functions properly only when the needs of the organisms (water, food, heat, oxygen and pressure) remain within the narrowly required limits. • Homeostasis: The tendency to maintain a stable internal environment. • Ex: Furnace and air conditioner unit to maintain constant temperature

5. Negative feedback mechanism: • Negative feedback occurs when an increase in some factor is sensed and is lowered • A response the body has to an occurrence that disturbs the homeostasis of the body. As the body reacts to that occurrence and moves closer to homeostasis, the receptors are shut down, thus causing fewer effectors to produce a product that’s needed to bring the body back to homeostasis, in the end having a “negative” effect on the production. The purpose of this is to stop overproduction or overreaction.

6. Homeostatic mechanism in regulating body temperature: • Shivering– in a cold environment muscles will contract involuntarily producing heat • Sweating- in an overheated environment the brain triggers a changes that promotes the increased loss of body heat

7. Managing glucose levels • Human body regulates the use & storage of glucose, a major cellular fuel • insulin reduces blood glucose levels • when glucose levels rise above set point, pancreas secretes insulin • promotes transport of glucose into cells & storage of glucose as glycogen in liver & muscle cells • dropping blood glucose levels • glucagon increases blood glucose levels • when glucose levels drop below set point, pancreas secretes glucagon • promotes breakdown of glycogen & release of glucose into the blood • increasing blood glucose levels Show PDF of insulin

8. Regulation: Maintaining Homeostasis • Balancing glucose levels in blood glucose uptake insulin pancreas depress appetite glucose storage glucose release stimulatehunger pancreas glucagon

9. Essential Nutrients • What happens if an animal’s diet is missing an essential nutrient? • deficiency diseases • scurvy — vitamin C (collagen production) • rickets — vitamin D (calcium absorption) • blindness — vitamin A (retinol production) • anemia — vitamin B12 (coenzyme function) • kwashiorkor — protein deficiency

10. Digestion • The reduction of large food molecules into smaller absorbable units and conversion of insoluble units into soluble ones. • This is accomplished by mechanical action, chemical and enzymatic action. • Enzymes are synthesized by cells in the mouth, stomach, pancreas and small intestine

11. Normally 92- 95% of a diet is digested and absorbed, but the process varied for each nutrient http://www.ama-assn.org/ama/pub/category/7155.html

12. Types of digestive action • Mechanical • Movement of the teeth grinding the food in the mouth • Chemical • Changing the food molecules into new and different molecules • Lipids Lipase Fatty acids + glycerol

13. Alimentary Tract • Alimentary canal • A muscular tube about 9 meters long • Appendage organs include: • Liver, biliary tree and pancreas • Extends from the mouth to the anus • Receives food . . . Digestion/absorption occurs . . .transport to cells . . .excretion of waste

14. Diagram of Alimentary canal • Peristalsis – propelling movements which are a forward motion that is wavelike • Peristalsis pushes tubular contents ahead of it through the alimentary canal

15. Mouth • Teeth mechanically grind and crush food • Saliva moistens and binds food mass • Salivary amylase begins digestion of starch • Chewed food mass bolus • Passes from mouth into esophagus • Movement is controlled by peristalsis

16. Approximately 1.5 liters of saliva are produced daily by salivary glands (~ 6 cups) Figure 12.1 • Amylase is a digestive enzyme • It splits starch and glycogen (both carbohydrates) into disaccharides via hydrolysis • Mucus binds food particles and acts as a lubricant in swallowing • Esophagus – straight tube that provides a passageway between the pharynx and stomach

17. Stomach • Chemical digestion begins in the middle of the stomach mixing food with gastric juices • Gastric juices contain HCl, intrinsic factor, pepsinogen, gastric lipase & mucus • Food becomes semi-liquid chyme (50% water) • Stomach is emptied in 1 – 4 hours • Sphincter–valves at either end of stomach

18. The lining of the stomach is covered with numerous small holes. These are the openings of gastric pits which extend into the mucosa forming gastric glands.

19. Stomach helps to initiate the digestion of proteins, but also helps speed up the digestion of carbohydrates and fats • Pepsin is the most important digestive enzyme in the stomach • Pepsin is a protein-splitting enzyme • It carries on a limited amount of absorption

20. The pyloric sphincter (pylorus) is a muscle that acts as a valve to prevent regurgitation of food from intestines back into the stomach

21. Rugae: thick folds in stomach wall

22. Pancreas • Functions as an endocrine gland • Releases hormones • Functions as an exocrine gland • Secretes digestive juices • Pancreatic juices move into the intestine (duodenum) • Contains enzymes that digest carbohydrates, fats, proteins and nucleic acids

23. Viewing the digestive system in the anatomical position, the pancreas is found in under the stomach in the left hypochondriac & epigastric regions

24. Liver • Located below the diaphragm in the right hypochondriac and epigastric regions of the abdominal area.

26. The liver metabolizes carbohydrates lipids and proteins • Stores glycogen, vitamins A, D, B12 and iron • Filters blood • Detoxifies blood • Secretes bile • An Introduction to the Liver– PDF File

27. Other functions of the liver • Producing quick energy when it is needed;  • Manufacturing new body proteins;  • Preventing shortages in body fuel by storing certain vitamins, minerals, and sugars;  • Regulating transport of fat stores;  • Regulating blood clotting;  • Aiding in the digestive process by producing bile;  • Controlling the production and excretion of cholesterol;  • Neutralizing and destroying poisonous substances;  • Metabolizing alcohol;  • Monitoring and maintaining the proper level of many chemicals and drugs in the blood;  • Cleansing the blood and discharging waste products into the bile;  • Maintaining hormone balance;  • Serving as the main organ of blood formation before birth;  • Helping the body resist infection by producing immune factors and by removing bacteria from the bloodstream;  • Regenerating its own damaged tissue; and  • Storing iron.

28. Bile - • Yellowish, green liquid made of bile salts, bile pigments, water, cholesterol and electrolytes • Bile salts aid the digestive enzymes and enhance the absorption of fatty acids and fat-soluble vitamins • Bile salts act as emulsifiers, breaking up fat into droplets, allowing lipases to digest them better 5.1.3 state source of one lipase – substate, source and optimum pH

29. Bile is stored in the gall bladder until a hormone stimulates its release into the small intestines http://www.foxriverwatch.com/liver_hepatic_damage_pcbs_1a.html

30. Small Intestine • Approx. 20 -25 feet long with villi and microvilli for a total surface area of 25 sq meters • 3 areas: • Duodenum • Jejunum • Ileum • Most digestion occurs in the duodenum • Most absorption occurs in the jejunum and ileum

31. The intestines are lined with villi • Increase the surface area of the intestinal lining • Increase the absorption of digestive products • Capillaries carry away absorbed products from villi • Nutrients are absorbed by several means • Simple diffusion (higher to lower concentration area) • Facilitated diffusion (Against the gradient using channel or carrier proteins) • Active transport (diffusion with ATP)

32. Microvilli on intestinal epithelial cells

33. As chyme enters duodenum it stimulates the release of pancreatic juices and mixes with enzymes from the pancreas and small intestine as well as with bile, fluid and bicarbonates • All the gastric, small intestinal secretions and pancreatic secretions are controlled by the nervous system and by hormones

34. Digestive enzymes in sm. intestine • Enzymes are specific to a particular substrate • Proteins • Peptidases break peptides into amino acids • Lipids • Lipases break lipids into glycerol and fatty acids

35. Carbohydrate Digestion • Begins in mouth with salivary amylase • Halted by hydrochloric acid • Digestion mostly occurs in small intestine by pancreatic amylase • Passes through intestinal wall in monosaccharide form (ex: glucose)

36. They quickly move through the digestive system • Some carbohydrates cannot be digested by humans and are excreted • They provide short term energy

37. Protein Digestion • Begins in stomach by proteolytic enzymes • Most of digestion takes place in the duodenum by pancreatic and intestinal enzymes: Protein hydrolysis • Final phase occurs in the “brush border” of the microvilli • Absorbed in the amino acid form • Allergic reactions can occur when intact proteins pass through intestinal wall

38. Proteins move through digestive system 2nd fastest after carbohydrates • Once protein is broken down into amino acids, these are reassembled into 1º,2º,3º and 4º proteins the body needs: • Hemoglobin – blood protein • Albumin – in plasma; aids in blood clotting • Fibrinogen – blood clotting agent

39. Lipid Digestion • Begins in stomach with gastric lipase • Major digestion occurs in small intestine • Bile and action of stomach/small intestine break down large globules into smaller pieces • Lipase breaks down particles into fatty acids. • Cholesterol and fat soluble vitamins follow similar process

40. Lipids move slowly through the digestive system • They are stored as long term storage in the form of adipose tissue http://www.sunyniagara.cc.ny.us/val/adipose2.html http://www.gen.umn.edu/courses/1135/lab/kidneylab/kidneylab.html

41. Vitamins, Minerals and Fluids • Absorbed in the intestine • Eight liters of fluid are passed back and forth across the membrane of small intestine to keep nutrients in solution • Vitamins and water pass unchanged from small intestinal wall into the blood stream • Absorption of mineral occurs in stages in small intestine

42. Large Intestine • Includes: • Ascending colon • transverse colon • descending colon • sigmoid colon • rectum http://www.fruit-eze.com/education/colon/

43. Large intestine primarily absorbs water, electrolytes and some vitamins • Bacteria break down undigested material • Formation and absorption of vitamin K • Formation and excretion of waste products http://www.fujinon.com/product/medical/ed0114.htm

44. Little digestion now occurs as it is mostly completed by this time. • Large intestine are about 5 feet long • Mixing movement and peristalsis occur but are much slower here. • Peristalsis occurs only 2 to 3 times/day.

45. Contain E. Coli (good form not 0157) that break down remaining food and aid in the formation of vitamin K • Newborns and vitamin K • The solid waste consists of dead bacteria, undigested fiber and other products of digestion.