Chapter Lecture Chapter 3: The Human Body: Are We Really What We Eat? © 2017 Pearson Education, Inc Why Do We Want to Eat? • Hunger: physiological drive for food • Nonspecific • Can be satisfied by a variety of different foods • Appetite: psychological desire to consume specific foods • Aroused by environmental cues • Anorexia: physiological need for food, yet no appetite • Can occur with illnesses or side effect of medication © 2017 Pearson Education, Inc Why Do We Want to Eat? (cont.) • Role of nerve cells • Hypothalamus triggers feelings of hunger or satiation (fullness) • Integrates signals from nerve cells in other body regions and from chemical messengers • Special cells lining the stomach and small intestine send signals to the brain to indicate if they are full or empty © 2017 Pearson Education, Inc © 2017 Pearson Education, Inc Why Do We Want to Eat? (cont.) • Role of hormones • Hormones: chemical messengers secreted into the bloodstream by endocrine glands to help regulate body functions • Pancreatic hormones, insulin and glucagon, maintain blood glucose levels • Ghrelin and cholesytokinin control hunger and satiety • Leptin acts on the hypothalamus to suppress hunger © 2017 Pearson Education, Inc Why Do We Want to Eat? (cont.) • Foods have differing effects on our feelings of hunger • Proteins have the highest satiety value • High-fat diets have a higher satiety value than high-carbohydrate diets • Bulky meals (high in fiber and water) distend the stomach and promote a sense of satiety • Solid foods are more filling than semisolid foods or liquids © 2017 Pearson Education, Inc Why Do We Want to Eat? (cont.) • Foods stimulate our senses: • Sight • Smell • Taste • Texture (mouth feel) • Hearing • Social and cultural cues • Learned experiences © 2017 Pearson Education, Inc © 2017 Pearson Education, Inc What Happens to the Food We Eat? • Food undergoes three processes: • Digestion: large food molecules are broken down to smaller molecules, mechanically and chemically • Absorption: process of taking these products through the intestinal wall • Elimination: undigested portions of food and waste products are removed from the body © 2017 Pearson Education, Inc What Happens to the Food We Eat? (cont.) • Gastrointestinal (GI) tract: • A series of organs arranged in a long tube that work together to process foods • The GI tract includes: • Organs such as the stomach, intestines • Sphincters: muscles that control the passage of food material from one organ to the next © 2017 Pearson Education, Inc © 2017 Pearson Education, Inc Digestive Disorders (cont.) • Causes of GERD include • Hiatal hernia • Cigarette smoking or alcohol use • Being overweight • Pregnancy • Chocolate, citrus, spicy or fried foods • Large high-fat meal Lying down soon after a meal â 2017 Pearson Education, Inc Digestive Disorders (cont.) • Peptic ulcers are areas of the GI tract that have been eroded by HCL and pepsin • Bacterium Helicobacter pylori plays a key role in development of both gastric and duodenal ulcers • Some ulcers are caused by prolonged use of non-steroidal anti-inflammatory drugs (NSAIDS) © 2017 Pearson Education, Inc © 2017 Pearson Education, Inc Digestive Disorders (cont.) • Food intolerance is a cluster of GI symptoms (gas, pain, diarrhea) that occur following consumption of a particular food • Food allergy is a hypersensitivity reaction of the immune system to a particular component (usually a protein) in a food © 2017 Pearson Education, Inc ABC News Video: Medical Mystery: Young Boy Allergic to Food © 2017 Pearson Education, Inc Digestive Disorders (cont.) • Celiac disease (celiac sprue) • Damaged small intestine lining (decreased villi and enzymes) reduces nutrient absorption • Offending component is gliadin (a protein in gluten), which is found in wheat, rye, and barley • No cure for celiac disease, treatment is with a special diet free of wheat, rye and barley © 2017 Pearson Education, Inc Digestive Disorders (cont.) • Non-celiac gluten sensitivity • Signs and symptoms can vary greatly • Bloating and diarrhea • Bone and joint pain • Depression and confusion • Vomiting reflex is triggered when substances stimulate brain cells to signal "backwards" peristalsis • Cyclic vomiting syndrome (CVS) is a chronic condition of recurring cycles that can last for hours or days © 2017 Pearson Education, Inc Digestive Disorders (cont.) • Crohn's disease • This inflammatory bowel disease can affect any area of the GI tract • Possible cause is immune system reaction to a virus or bacteria • Symptoms include diarrhea, abdominal pain, rectal bleeding, weight loss, fever, anemia Children can experience delayed growth â 2017 Pearson Education, Inc Digestive Disorders (cont.) • Ulcerative colitis • Chronic disease characterized by inflammation and ulceration of the mucosa, the innermost lining of the colon • Possible cause is an immune response to a virus or bacteria • Symptoms are similar to Crohn's disease • Although not caused by food, patients may have to avoid foods that cause GI discomfort © 2017 Pearson Education, Inc Digestive Disorders (cont.) • Diarrhea • Frequent passage of loose, watery stools • Usually caused by infection of the GI tract, stress, food intolerances, reactions to medications, or bowel disorders • Can lead to severe dehydration • More dangerous for children and the elderly • Traveler's diarrhea: common concern; also called dysentery © 2017 Pearson Education, Inc © 2017 Pearson Education, Inc Digestive Disorders (cont.) • Constipation • Infrequent hard, small, difficult-to-pass stools • Prevention includes increasing fiber-rich foods and fluids, and regular exercise © 2017 Pearson Education, Inc Digestive Disorders (cont.) • Irritable bowel syndrome (IBS) is a disorder that interferes with normal colon function • Symptoms include abdominal cramps, bloating, and either diarrhea or constipation • Associated with stress, caffeine, large meals, chocolate, alcohol, dairy, wheat • Treatment includes stress management, smaller meals, high-fiber diet, fluids, and regular physical activity © 2017 Pearson Education, Inc Cancer in the GI System • Cancer can develop in any region of the GI tract, gallbladder, liver, or pancreas • Most common GI cancer is colorectal cancer • Smoking, obesity, a diet high in red or processed meats and low in fruits and vegetables increase risk • Colonoscopy can detect cancer and precancerous polyps © 2017 Pearson Education, Inc ... moistened in the mouth is called bolus • The epiglottis covers the opening to the trachea during swallowing • The esophagus propels food from the mouth to the stomach • Peristalsis is the muscular... series of organs arranged in a long tube that work together to process foods • The GI tract includes: • Organs such as the stomach, intestines • Sphincters: muscles that control the passage of food... neutralizes the acid near the surface of the stomach's lining © 2017 Pearson Education, Inc © 2017 Pearson Education, Inc Digestion in the Small Intestine • Small intestine is composed of three