Lecture 13 BIO 311D 1st Edition Outline of Last Lecture I Stages of Food Processing II Intracellular Extracellular Digestion III Main Stages of Food Processing IV Digestion in the Stomach and Small Intestine V Pancreas Secretions VI Absorption of the Large Intestine Outline of Current Lecture I Dental Adaptations II Stomach Intestinal and Mutualistic Adaptations III Regulation of Digestion IV Regulation of Appetite and Consumption V Obesity and Evolution Current Lecture Dental 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 venom Stomach 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 vegetation Mutualistic Adaptations Many herbivores have fermentation chambers where mutualistic microorganisms digest cellulose The most elaborate adaptations for an herbivorous diet have evolved in the animals called ruminants Secretion modulates digestion by A Acting as an enzyme in the duodenum B Triggering bile release into the intestine C Triggering buffer release from the pancreas D Acting as an enzyme in the stomach E 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 environment Regulation 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 hormones Glugacon the pancreatic hormone functions to A Stimulate hunger B Inhibit activity in the small intestine C Increase fat storage in fat cells D Reduce glucose levels in the blood E Stimulate the liver to release glucose Regulation 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 tissue Glucose 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 glucose Increased 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 Ghrelin D Insulin E Secretin Regulation 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 appetite Obesity 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 famines
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