Chapters 3-5 Notes
Chapters 3-5 Notes HUN1201-0006
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Date Created: 10/04/15
Chapter 3 Notes Why do we want to eat physiologic drive for food Nonspecific Can be satisfied by a variety of different foods psychological desire to consume specific foods Aroused by environmental cues physiological need for food but no appetite What tells us we re hungry triggers feelings of hunger or satation fullness Located above pituitary gland amp the brain stem in the area of the brain that regulates involuntary actions Integrates signals from the nerve cells chemical messengers hormones and the tpyes of food consumed The role of the nerve cells and hunger 0 Special cells lining the stomach and the small intestine detect changes in the pressure which tell whether your stomach is full or not 0 Then the cells send signals to the hypothalamus The role of hormones in hunger chemical messengers secreted into the bloodstream by endocrine glands to help regulate body functions Pancreatic hormones insulin amp glucagon maintain blood glucose levels Feling full signals from your stomach increase in glucose levels The role of food type in hunger o Proteinrich foods have the highest satiety values 0 High fat diets have a high satiety value more than high carb diets o Bulky meals distend the stomach and promote a sense of satiety 0 Solid foods are more filling than semisolid foods or beverages What happens to the food we eat 3 Processes 1 large food molecules are broken down to smaller molecules mechanically and chemically 2 process of taking these products through the wall of the intestines 3 undigested portions of food and waste products are remove from the body The GI Tract 0 Series of m arranged in a tube that work together to process food muscles that control the passage of food materials from one organ to the next Cephalic phase of digestion o Hunger and appetite work together to prepare for digestion 0 1st thought of food stimulates the release of digestive juices Digestion begins in the mouth 0 Chewing moistens the food amp mechanically breaks it into smaller pieces exposes more chemicals to digestive juices o Saliva contains digestive juices secreted by the salivary glands in the mouth 0 Taste receptors detect distinct tastes bitter sweet salty sour unami o Olfactory receptors detect the smell of food Components of saliva chemicals that induce changes in other chemicals to speed up bodily processes Salivary amylase begins chemical digestion o Bicarbonates neutralize acids Chewing and swallowing mass of food chewedmoistened in the mouth covers opening to the trachea during swallowing 0 Food travels from the mouth to the stomach through the esophagus muscular contractions that move through the GI Tract The pH scale I potential of hydrogen 0 Measures the potential of a substance to release or take up hydrogen ions in a solution acidity or alkalinity Digestion in the stomach hormone secreted by stomach lining cells that stimulates the gastric glands to produce gastric juice 0 Gastric Glands Parietal cells secrete hydrochloric acid and intrinsic factor Chief cells secrete pepsinogen and gastric juice 0 Gastric Juice contains HCL denatures protein and activates pepsin Pepsin enzyme to digest carbs Gastric Lipase enzyme to digest fat Intrinsic Factor protein to absorb BlZ Occurs in the stomach mixes and churns food and gastric juices liquid product of mechanical and chemical digestion in the stomach protects the stomach from acid in gastric juices Digestion in the small intestine o 3 Sections duodenum jejunum ileum connects the small intestine to the large 0 Most digestion takes place in the small intestine Digestion in the large intestine 0 Also referred to as the colon 0 Main function store undigested food material and absorb water short chain fatty acids and feces Enzymes speed up digestion o Enzymes guide digestion through chemical reaction that breaks down substances by addition of water 0 Specific to carb fat and protein digestion Hormones assist in digestion 0 Released into the bloodstream amp act on specific target cells that contain the receptor protein for that given hormone o Hormones bind to the receptor proteins on the cell membrane and activate a 2quot l messenger system within the cell to achieve the targeted response 0 Key hormones involved in digestion stimulates secretion of HCL amp pepsinogen amp gastric motility stimulates secretion of pancreatic bicarbonate amp gastric motility stimulates secretion of pancreatic digestive enzymes amp gallbladder contraction inhibits gastric acid secretion ampslows gastric emptying o Hormones with potential digestive roles somatostatin amp ghrelin Accessory Organs 0 Produce store and secrete enzymes and other chemicals that are involved in digestion Gallbladder Pancreas Liver Gallbladder o Stores produced in the liver 0 CCK signals to release bile o Bile imulsifies the lipids Lipids are dispersed into smaller globules and become more accessible to the digestive enzymes Pancreas o Manufactures holds and secretes digestive enzymes 0 Stores enzymes in their inactive form Pancreatic amylase digests carbs Lipase digests fats Protease digests proteins 0 Insulin and glucagon are produced to regulate blood glucose 0 Synthesizes chemicals for metabolism 0 Receives he products of digestion via the portal vein 0 Releases glucose from glucagon stores 0 Stores vitamins amp manufactures blood proteins 0 Filters the blood Absorption 0 Process of taking molecules across a cell membrane and into the cells of the body Small amount occurs in the stomach and large intestine Most occurs in the small intestine lining of the GI tract folds in the lining that allow it to absorb nutrients absorptive cells in the villi composed of microvilli greatly increases the absorptive capacity 4 Types of Absorption in the Small Intestine 1 nutrients simply pass through the enterocytes and into the bloodstream without the use of a carrier or energy 2 requires a carrier protein requires energy and a protein carrier to transport nutrients 4 active transport by which a small amount of intestinal contents is engulfed by the cell membrane into the cell 9quot Transport of Nutrients and Wastes 0 Blood travels through the cardiovascular system and delivers nutrients to the tissues and picks up waste products o Lymph travels through the lymphatic system lacteals pick up most lipids and fat soluble vitamins clusters of immune cells that filter microbes and other harmful agents Muscles of the GI Tract due to the action of circular muscles and longitudinal muscles the run along the entre GI tract Segmentation rhythmic contraction of circular muscles in the intestinal wall Enteric Nervous System 0 Controls contraction and secretions of the GI tract o In the gut wall Chapter 4 Notes What are Carbohydrates o Macronutrients 0 Important source of energy for all cells 0 Preferred energy source for nerve cells 0 Composed of carbon hydrogen and oxygen Glucose Most abundant carb Produced by plants during photosynthesis Simple Carbs 0 Contain 1 or 2 molecules sugars o 1molecule Glucose fructose and galactose o molecules Lactose maltose sucrose Lactose glucose galactose Maltose glucose glucose Sucrose glucose fructose Complex Carbs o 310 monosaccharides o 100s1000s of glucose molecules Complex Carbohydrates Starch 0 Plants store carbs as starch polysaccharides o straight chain of glucose 0 branched chain of glucose 0 glucose molecules linked by beta bonds largely indigestibe Glycogen 0 Storage form of glucose for humans 0 Not found in food not a source of dietary carbs o Stored in the liver and muscles Fiber 0 Long polysaccharide chains 0 Dietary fibers nondigestible parts of plants 0 nondigestible forms of carbs extracted from plants and have known health benefits 0 Total fiber dietary fiber functional fiber Soluble Fibers o Dissolve in water viscous and gelforming o Fermentable digested by intestinal bacteria 0 Found in citrus berries oats and beans 0 Ex pectin gum mucilage Insoluble fibers 0 Nonviscous can t be fermented by colon bacteria 0 Ex cellulose hemicelluloses Carbohydrate Digestion enzyme that begins chemical digestion breaks carbs down to maltose o Carb digestion DOES NOT occur in the stomach Stomach acids inactivate salivary amylase 0 Most chemical digestion of carbs occurs in the small intestine enzyme produced in the pancreas and secreted into the small intestine digests carbs to maltose 0 Additional enzymes in the microvilli digest disaccharides to monosaccharides maltose sucrose lactase o Monosaccharides are absorbed into the cells lining the small intestine and then enter the bloodstream Lactose Intolerance 0 Insufficient enzyme lactase to digest the lactose containing foods Carbohydrate Digestion Cont o All monosaccharides are converted to glucose by the liver 0 Glucose circulating in our blood is our primary source of energy 0 Excess glucose is stored as glycogen in the liver amp muscles 0 We don t have the enzymes necessary to digest M o Bacteria in the large intestine can break down some fiber 0 Most fiber remains undigested amp is excreted in the feces Blood Glucose Regulation 0 Blood glucose levels must be closely regulated o Hormones control blood glucose levels insulin glucagon epinephrine norepinephrine cortisol growth hormone o Insulin Secreted by beta cells in the pancreas Stimulates glucose transporters carrier proteins to help take glucose from the blood across the cell membrane Stimulates the liver to take up glucose and convert it to glycogen o Glucagon Secreted by alpha cells in the pancreas Stimulates the liver to convert glycogen to glucose Stimulate the production of glucose from amino acids 0 Epinephrine amp norepinephrine Secreted by the adrenal glands and nerve endings when blood glucose is low Increase glycogen breakdown in the liver releasing glucose into the blood responsible for quotfight or flight o Cortisol amp Growth Hormone Secreted by the adrenal glands on act on the liver muscles and adipose tissue Cortisol increases gluconeogenesis and decreases muscle glucose use Growth hormone decreases muscle glucose uptake and increases fatty acid mobilization and increases liver glucose output a food s potential to raise blood glucose levels Foods with a high glycemic index cause a sudden surge in blood glucose Increase in insulin leads to a decrease in blood glucose Foods with a low glycemic index cause low to moderate fluctuations in blood glucose Not always easy to predict Food s absorption rate varies with the type of carb preparation methods and its fatfiber content Most foods are eaten in combination Determines the effect of a food on a person s glucose response Grams ofLrbs in a food are multiplied by the glycemic index of that carb 0 Benefits of lower glycemic index Less fluctuations in blood glucose Risk reduction for heart disease and colon cancer The Role of Carbohydrates 0 Energy Red blood cells use only glucose for energy Both carbs and fats supply energy Glucose is important for energy during exercise 0 Ketosis Fat breakdown during fasting forms keytones Excess ketones increase blood acidity and cause ketoacidosis Carbohydrates Spare Protein occurs when a diet is deficient in carbs o The body will make its own glucose from protein 0 Amino acids from these proteins can t be used to make new cells repair tissue support the immune system or perform any of the other functions Complex Carbs have Health Benefits 0 Fiber May reduce the risk of colon cancer Helps prevent intestinal problems Lower risk for type 2 diabetes Enhance weight loss How Much Carbs o RDA 130 gday to supply adequate glucose to the brain 0 AMDR 4565 of daily calories 0 Focus on fiber rich carbs Simple Carbs o Diets high in simple sugars cause tooth decay increase in bad cholesterol amp contribute to obesity Complex Carbs part 2 nutrients are lost during processing and have been added back so the food meet specified standard have nutrients added that didn t originally exist in the food inability to regulate blood glucose levels 0 Type 1 Accounts for 10 of all cases Body can t produce enough insulin Causes hyperglycemiarequires insulin injections Ay be an autoimmune disease Insulin insensitivity cells become less responsive to insulin Metabolic syndrome a cluster of risk factors that increase the risk for type 2 Causes genetics obesity and physical inactivity o Hypoglycemia Low blood glucose may cause shakiness anxiety sweating and weakness pancreas secretes too much insulin after a high carb meal pancreas produces too much insulin even when someone hasn t eaten Chapter 5 Notes What are Lipids o Lipids are molecules that do not dissolve in water insoluble o 3 types found n foods body tissues and cells Triglycerides Phospholipids Sterols o Fats are the lipid content of diets and food Triglycerides o 3 fatty acid molecules 1 glycerol molecule 0 Fatty acids are classified by carbon chain length saturation level and shape Chain Length 0 Carbons can be numbered carboxyl end COOH 0L carbon alpha 1 Methyl end CH3 Qcarbon omega last 0 Determines method of lipid digestion absorption metabolism and use Saturation o hydrogen atoms surrounding every carbon atom in the chain 1 double bond lacks 1 hydrogen atom less than 1 double bond O 0 Shape o Determined by the bonds of the carbon chains 0 pack tightly together are solid at room temperature 0 don t stack together well more liquid at room temperature Hydrogen atoms the unsaturated part can be arranged in different positions I same side of the carbon chain opposite sides of the chain Hydrogenation 0 Hydrogen atoms are added to unsaturated fatty acids 0 Makes oils more solid and saturated o Creates trans fatty acids 0 Reduce oxidation resist rancidity 0 Increase risk of cardiovascular disease Essential Fatty Acids 0 Cannot be made by the body must be obtained through food 0 Linoleic acid cu3 fatty acid found in veggies amp nut oils 0 Alphalinoleic acid co3 fatty acid found in veggies soy flaxseed walnuts 003 Fatty Acids 0 Fish and fish oil 0 Eicoapentaenoic acid EPA o Docosahexaenoic acid DHA 0 Reduce risk of heart disease 0 Regulate prostaglandins PGs and thromboxanes TXs reduce inflammatory responses 0 Reduce blood clotting and plasma triglycerides Phospholipids o Glycerol backbone 2 fatty acids phosphate 0 Soluble in water 0 Transport fat in the bloodstream o Manufactured in our bodies Sterols 0 Contains multiple rings of cholesterol atoms 0 Plant sterols block the absorption of dietary cholesterols 0 Cholesterol is made in our bodies not necessary in the exogenous diet 0 sex hormones vitamin D bile Digestion of fats 0 fat digestion begins in the small intestine o Cholecystokinin CCK amp secretin gallbladder contractions release bile o Bile is produced in them and is stored in the gallbladder o Bile emulsifies fat into small droplets o Pancreatic enzymes break fat into 2 fatty acids and a monoglyceride Absorption of Fats transports lipids for absorption lipoprotein produced in intestine to transport lipids from a meal Composed of fatty acids surrounded by phospholipids and proteins Soluble in water Formed in the intestinal cells Travel through the lymphatic system Transferred to the bloodstream 0 Short and medium fatty acid chains Not arranged in chylomicrons Absorbed more quickly 0 Triglycerides in the chylomicrons Disassembled by lipoprotein lipase before they can enter body cells o In body cells triglycerides can be Used immediately for energy Used to make lipid containing compounds Stored in muscle and adipose tissues The Roles of Fat 2 kcal per gram Major fuel at rest Endurance exercise Essential fatty acids Fatsoluble vitamins Regulates cell function Maintains membrane Protects the body Provides flavors and textures for foods Helps us feel satisfied How much fat AMDR for fat 2035 Decreases saturated and trans fatty acid intake lowers risk of heart disease Active people may need more energy from Lrbs and can reduce their fat intake 2025 of total calories DRIs set for essential fatty acids Linoleic acid AMDR of 510 of energy Alphalinoleic acid 0612 of energy 51 to 101 ratio of linoleic alphalinoleic acid saturated fat less than 10 of energy E fat reduced to the absolute minimum Food Sources of Fat fats we add to foods ie butter cream mayo salad dressing fats hidden within foods ie baked goods dairy meats fast foods occur naturally or added during processing beneficial fats 003 fatty acids may be low in diets fish walnuts soy canola flaxseed switch to more healthful fats wout increasing total fat intake fat replacers used to lower fat content of foods found in chips cakes cookies may cause GI side effect in large amounts Cardiovascular Disease dysfunction of the heart or blood vessels can result in a heart attack or stroke Risk factors being overweight physical inactivity smoking increased blood pressure diabetes mellitus inflammation Dietary fats increase blood lipids Highly saturated and trans fat intakes increase blood cholesterol Omega3 fatty acids decrease inflammation and blood triglycerides Blood lipids include Chylomicrons present only after a meal Very low density lipoproteins Low density lipoproteins High density lipoproteins
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