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Lecture 2

NUTR1010 Week 2

7 Pages
94 Views

Department
Nutrition
Course Code
NUTR 1010
Professor
Laura E Forbes

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Description
WEEK 2 Nutrition (Digestion) Why do we eat? Hunger • physiological need for food Appetite • "that cake looks good" • "I had to have it" How does out body tell us we're hungry? • Nerve signals • --> Your stomach and intestines send nerve signals to the hypothalamus of the brain • Blood sugar levels drop • --> insulin and glucagon levels in the blood change • --> this is a signal for your hypothalamus (time to eat) • Lots of other hormones have a role too .. it's complicated Your digestive system does 3 things 1. Digestion • Breaking food into tiny pieces 2. Absorption • Moving the tiny pieces from the intestine to blood stream 3. Elimination • Getting rid of waste Introducing Enzymes • An important part of chemical digestion • Made of protein • Biological catalysts • --> facilitate chemical reactions in living things • When it ends in -ASE .. It's an enzyme Introducing GI Tract • Cephalic Phase of Digestion • --> when the body is getting ready to receive food (i.e., salivating) Digestion starts in the mouth • 1. Mechanical Digestion • Your teeth break up food • 2. Chemical Digestion • Enzymes in your saliva start breaking up food • Salivary Amylase breaks up starch • Lingual Lipase breaks up fat • 3. Making a bolus • moist ball of food Swallowing • Part conscious, part unconscious In the Esophagus • Peristalsis • --> waves of muscular contractions that move the food • --> inner circular muscles • --> outer lengthwise muscles • Peristalsis starts in the esophagus and continues all the way through the GI tract • Food moves into the stomach via the lower esophageal sphincter The stomach (mechanical) • --> 3 thick muscle laters churn and break up food • --> food turns to chyme The stomach (chemical) • Hydrochloric acid (HCl) denatures protein (unravels) • pH of gastric juice is 2.0 (1 is most acidic) • Pepsin (an enzyme) breaks down protein Mucus • Mucus lines your entire GI tract • --> protects, helps food move easily • Mucus is especially important in the stomach • --> stomach is made of muscle (protein) • --> mucus stops you from digesting your stomach Entering the Small Intestine • Chyme is delivered from the stomach through the pyloric sphincter • In the duodenum (1st part of small intestine) • Lots of chemicals and enzymes are added - the liver, the gallbladder, pancreas The liver and gallbladder • Bile is made in the liver • It;'s stored in the gall bladder • --> the gall bladder adds bile • --> bile emulsifies the fat, it breaks it into small droplets that mix well with water The pancreas (enzyme production) • The pancreas produces and adds … • --> bicarbonate to neutralize the acid • --> enzymes! (pancreatic amylase for starch, lipase for fat, protease for protein) Moving in the Small Intestine • Duodenum - chemical digestion and some absorption • Jejunum - digestion continues, lots of absorption • Ileum - absorption continues and leftovers are passed to the large intestine • villi: finger like absorbers along the small intestine • microvilli: villi on the villi, villi on villi, villi city population the small intestine Getting nutrients into cells • Diffusion (eg, water) • Facilitated diffusion (carrier molecule) • Active Transport (carrier molecule) (requires NRG) (kcal) Where do the nutrients go? • Into the blood and lymph • Nutrients are then processed and/or burnt for energy • More information on Friday! The Large Intestine • cecunum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal, anus Large Intestine's Important Functions • Water absorption • Contains friendly bacteria • --> digests fiber • --> produces gas and vitamin K • --> produces fats that the large intestine uses • rectum holds feces until it's eliminated Borborygmus • Technical term for stomach growling • movement of gases in the intestines • doesn't necessarily mean you're hungry When Digestion Goes Wrong • learn about some common digestive problems • heart burn, intolerances, allergies, celiac disease, constipation, diarrhea Heart Burn • Gastroesophagael reflux disease (GERD) • Chyme from the stomach in the esophagus • Lower oesophageal sphincter may be damaged, or just not working hard enough • it burns because of the HCl from the stomach Causes of Heart Burn • Genetics (dysfunctional) • Physical Damage (dysfunctional) (ED) • Pregnancy (extra sphincter pressure) • Hiatal hernia* (extra sphincter pressure) • Overweight/obesity (extra sphincter pressure) Hiatal Hernia • If the diaphragm is weak at the point of the lower esophageal sphincter, it might not repress the sphincter enough Dietary.lifestyle contributors • Chemically affect muscle tone of the digestive tract/lower esophageal sphincter • --> high fat foods • --> smoking • --> alcohol • --> spicy foods • --> caffeine What to do • Avoid high fat, spicy meals • avoid caffeine and alcohol • eat small meals • drink between meals, not with meals • don't lie down for at least 1 hour after a meal Intolerances andAllergies • Intol
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