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UT BIO 311D - Animal Nutrition (Part II)
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Lecture 13 BIO 311D 1st EditionOutline of Last Lecture I. Stages of Food ProcessingII. Intracellular/Extracellular DigestionIII. Main Stages of Food ProcessingIV. Digestion in the Stomach and Small Intestine V. Pancreas SecretionsVI. Absorption of the Large IntestineOutline of Current Lecture I. Dental AdaptationsII. Stomach, Intestinal, and Mutualistic AdaptationsIII. Regulation of DigestionIV. Regulation of Appetite and ConsumptionV. Obesity and EvolutionCurrent LectureDental Adaptations:• Dentition, an animal’s assortment of teeth, is one example of structural variation reflecting diet• The success of mammals is due in part to their dentition, which is specialized for different diets• Nonmammalian vertebrates have less specialized teeth, though exceptions exist– For example, the teeth of poisonous snakes are modified as fangs for injecting venomStomach and Intestinal Adaptations• Many carnivores have large, expandable stomachs• Herbivores and omnivores generally have longer alimentary canals than carnivores, reflecting the longer time needed to digest vegetationMutualistic Adaptations• Many herbivores have fermentation chambers, where mutualistic microorganisms digestcellulose• The most elaborate adaptations for an herbivorous diet have evolved in the animals called ruminantsSecretion modulates digestion byA. Acting as an enzyme in the duodenumB. Triggering bile release into the intestineC. Triggering buffer release from the pancreasD. Acting as an enzyme in the stomachE. Triggering acid release in the stomach (gastrin is responsible for this)Feedback circuits regulate digestion, energy storage, and appetite• The intake of food and the use of nutrients vary with an animal’s diet and environmentRegulation of Digestion• Each step in the digestive system is activated as needed• The enteric division of the nervous system helps to regulate the digestive process• The endocrine system also regulates digestion through the release and transport of hormonesGlugacon, the pancreatic hormone functions to A. Stimulate hungerB. Inhibit activity in the small intestineC. Increase fat storage in fat cellsD. Reduce glucose levels in the bloodE. Stimulate the liver to release glucoseRegulation of Energy Storage• The body stores energy-rich molecules that are not needed right away for metabolism• In humans, energy is stored first in the liver and muscle cells in the polymer glycogen• Excess energy is stored in adipose tissue, the most space-efficient storage tissueGlucose Homeostasis• Oxidation of glucose generates ATP to fuel cellular processes• The hormones insulin and glucagon regulate the breakdown of glycogen into glucose• The liver is the site for glucose homeostasis– A carbohydrate-rich meal raises insulin levels, which triggers the synthesis of glycogen– Low blood sugar causes glucagon to stimulate the breakdown of glycogen and release glucoseIncreased appetite is the typical result of increased levels in the blood of A. Leptin (released from fat cells)B. PYY (released by small intestine)C. GhrelinD. Insulin E. SecretinRegulation of Appetite and Consumption• Overnourishment causes obesity, which results from excessive intake of food energy with the excess stored as fat• Obesity contributes to diabetes (type 2), cancer of the colon and breasts, heart attacks, and strokes• Researchers have discovered several of the mechanisms that help regulate body weight• Hormones regulate long-term and short-term appetite by affecting a “satiety center” in the brain• Studies on mice revealed that the hormone leptin plays an important role in regulating obesity• Leptin is produced by adipose tissue and can help to suppress appetiteObesity and Evolution• A species of birds called petrels becomes obese as chicks; in order to consume enough protein from high-fat food, chicks need to consume more calories than they burn• The problem of maintaining weight partly stems from our evolutionary past, when fat hoarding was a means of survival• Individuals who were more likely to eat fatty food and store energy as adipose tissue may have been more likely to survive


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UT BIO 311D - Animal Nutrition (Part II)

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