Chapter 3 Outline Are we really what we eat 1 Hunger 2 Appetite 3 Anorexia 4 Hypothalamus physiological drive for food that is nonspecific and can be satisfied by a variety of foods psychological desire to consume specific foods and is aroused by environment physiological need for food but no appetite triggers feelings of hunger or satiation fullness located above pituitary gland a b Send and receive chemical messengers hormones 5 Hormones chemical messengers secreted into blood by endocrine glands to regulate body functions a Pancreatic hormones insulin and glucagon maintain blood glucose b Released into bloodstream and act on specific target cells that contain the receptor protein for that given hormone c Bind to the receptor on cell membrane and activate a second messenger system within the cell to gastrin secretin CCK CIP somatostatin ghrelin achieve the targeted response d Key ones involved in digestion e Ones with potential digestive roles 6 Proteins have the highest satiety value feel fuller longer 7 High fat diets have a higher satiety value than high carb diets 8 Bulky meals 9 Solid foods 10 Senses like sight smell taste texture and hearing make us want to eat 11 Food processes Digestion Absorption Elimination 12 Digestion 13 Absorption high in fiber and water distend the stomach and promote a sense of satiety are more filling than semisolid or liquid foods large food broken down into smaller molecules mechanically and chemically process of taking in products through the intestinal wall across a cell membrane into cells of the body a Small amounts occur in stomach and large intestine b Most occurs in small intestine undigested portions of food and waste are eliminated from the body muscles that control the passage of food material from one organ to the next mouth pharynx esophagus stomach small and large intestine rectum produce store and secrete enzymes involved in digestion 14 Elimination 15 Sphincters 16 Organs of the GI tract 17 Accessory organs a Salivary glands b Liver synthesizes chemicals for metabolism i Receives products via the portal vein ii Releases glucose from glycogen stores iii Stores vitamins iv Manufactures blood proteins v Filters blood removing waste and toxins stores bile greenish fluid produced by liver signaled by CCK to release bile which c Gallbladder emulsifies lipis d Pancreas manufactures holds and secretes digestive enzymes i Stores inactive enzymes ii Amylase digests carbs iii Lipase digests fats iv Protease digests proteins 18 Hunger and appetite work together to prep GI tract for digestion a Begins with the first thought of food 1 Chapter 3 Outline Are we really what we eat 19 Digestion begins in the mouth moistens the food and breaks down food contains digestive juices secreted by the salivary gland a Chewing b Saliva c Taste receptors detect distinct tastes i Bitter sweet salty sour umami d Olfactory receptors detect aromas smells of foods 20 Enzymes are complex chemicals that induce chemical changes to speed up processes a Salivary amylase begins starch digestion b Specific to carb protein and fat digestion neutralize acids and lysozymes fight oral bacteria moistens the food and oral cavity the mass of food chewed and moistened in the mouth 21 Bicarbonates 22 Mucus 23 Antibodies 24 Bolus 25 Epiglottis 26 Food travels from the mouth to the stomach through the esophagus 27 Peristalsis 28 Segmentation 29 pH the muscular contractions that move food through the GI tract covers the opening to the trachea windpipe during swallowing mixes the chime and enhances its contact with digestive enzymes is the potential of hydrogen a b measure of acidity or alkalinity to take up or release hydrogen ions 30 Pure water is neutral and human blood is close to neutral 31 Tissues in the lining of the stomach are protected from the effects of acidity 32 Acid 33 Gastrin 34 Gastric Glands 0 6 Neutral 7 Basic 8 14 a Parietal cells secrete HCl and intrinsic factor b Chief cells secrete pepsinogen and gastric lipase 35 Gastric Juice contains a HCl denatures proteins and activates pepsin parietal b Pepsin enzyme to digest protein chief c Gastric lipase enzyme to digest fat chief d Intrinsic factor protein to absorb B12 parietal 36 Digestion in the stomach a hormone secreted by stomach lining cells that stimulates the gastric glands to produce gastric juice a Chyme liquid product of mechanical and chemical digestion in the stomach b Mucus layer that protects stomach lining from the acid in gastric juices c Bicarbonate neutralizes the acid d The stomach contracts and relaxes churning food and moves contents toward the pyloric sphincter 37 Small intestine composed of the duodenum jejunum and ileum a b Where the most digestion and absorption take place Lleocecal valve sphincter connects the small intestine to the large intestine 38 Large intestine function is to store undigested food and absorb water short chain fatty acids and elcetrolytes a also referred to as the colon 39 Hydrolysis a chemical reaction that breaks down substances by addition of water 2 Chapter 3 Outline Are we really what we eat 40 41 Absorption a Mucosal membrane the lining of the GI tract that has special structures b Villi folds in the lining that allow it to absorb more nutrients c Enterocytes absorptive cells in the villi d Capillaries and a lacteal small lymph vessel inside each villus e Brush border composed of microvilli greatly increases the surface area 42 Four types of absorption in small intestine a Passive diffusion carrier or energy by the cell membrane into the cell b Facilitated diffusion c Active transport d Endocytosis pinocytosis nutrients pass through the enterocytes and into bloodstream without the use of a requires a carrier protein requires energy and a protein carrier to transport nutrients active transport by which a small amount of intestinal contents is engulfed 43 Blood travels through cardiovascular system a Delivers nutrients to the tissues and picks up waste products travels through lymphatic system Lacteals pick up most lipids and fat soluble vitamins Lymph nodes are clusters of immune cells that filter microbes and other harmful agents 44 Lymph a b 45 Colon a Haustra are segmentations in the colon that contract slowly to move contents b Mass movement occasionally occurs to move wastes toward the rectum 46 Muscle contraction rate a Stomach 3 times a minute b Small intestine up to 10 times a minute c Haustra 2 times per hours are in the mouth take over in the GI
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