BIOPSYCH 0505 1nd Edition Exam 3 Study Guide Lectures 17 25 Lecture 17 March 17th I Energy A Energy delivered 1 Lipids fats 2 Amino acids proteins 3 Glucose sugars B Energy stored 1 Fat can store twice as much energy as glycogen Fatty acids are broken down to glycerol which then has to be further converted to glucose 2 Protein 3 Glycogen small percentage stored in the body because it is a much heavier molecule and has a tendency to hold water II Three places of energy metabolism A Cephalic phase 1 Preparatory phase which is initiated by the sight or smell of food 2 Insulin levels rise increased insulin tries to remove the glucose in the body so it can be stored for later use 3 Glucagon levels are low pancreatic hormone that converts glycogen back into useable glucose B Absorptive phase 1 Nutrients from a meal meeting the body s immediate energy requirements with the excess being stored 2 Insulin levels remain high 3 Glucagon energy remains low C Fasting phase 1 Energy being withdrawn from stores to meet the body s immediate needs 2 Nothing left for absorption occurs four hours after you eat 3 Glucagon levels are high as insulin levels are low III Eating A What we eat 1 Evolution of tastes humans have a tendency to prefer food higher in fats salts and sugars 2 In nature foods that are fatty and sweet are usually higher in nutrients and energy than less sweet or fatty foods 3 Salty foods are high in sodium which are needed for electrolyte balance in the body 4 Bitter tastes are not a favorite because bitter things are typically associated with toxins 5 Modeling of food preferences prefer flavors found in mother s milk and on the breath of others 6 Vitamins and minerals we prefer foods that are good sources of vitamins and minerals especially if there is a deficiency B When do we eat 1 Pre meal hunger feel more hungry in the cephalic stage thoughts of food make you more hungry 2 Conditioning of Hunger time of day you are supposed to be hungry because it s the usual time you eat Lecture 18 March 25th How much to we eat I Hunger Peptides A Ghrelin 1 Produced and released by the stomach and a little is produced by duodenum and the pancreas 2 Levels increase during fasting and are highest before meals which results in perception of hunger 3 Levels then decrease after meals B Neuropeptide Y 1 Released in the hypothalamus specifically the arcuate nucleus 2 Increases appetite and is a potent stimulator of eating behavior 3 Higher levels correlate with hunger as lower levels are correlated to not eating even when food is available 4 Levels increase during fasting II Satiety Signals opposite of hunger signals A What they do 1 Help you to stop eating when you are full 2 Influenced by the food in gut the slower you eat the faster you will feel full 3 Influenced by glucose in the blood when it is high the body will know that you should stop eating 4 Influenced by the volume of food how much pressure is put on volume receptors 5 Also the nutritive density of food how high in sugar vitamins fats and energy is in the food the more nutrients the less you eat B 2 phenomenoms 1 Appetizer effect and satiety having an appetizer before a meal will make you more hungry triggers the cephalic phase with increased insulin levels 2 Social influences and satiety you eat more when with your friends prompted by others eating C Sensory Specific Satiety 1 Foods consumed and the sensory experience 2 Tasting food immediately decreases the positive incentive value of similar tastes 3 Decreases the palatability of all foods about 30 minutes later 4 Is adaptive and encourages a varied diet 5 There are some foods resistant to sensory specific satiety bread potatoes milk rice sweets salads III Satiety peptides A CCK 1 Secreted by the small intestines in response to fats 2 Higher levels of fats are signals of higher nutritional value 3 Slows down the rate of stomach emptying 4 Your intestines need time to absorb the nutrients so if you push too much food in the intestines at one time only a little bit of nutrients will get absorbed B Peptide YY 1 Secreted by cells in the ileum small intestines and the colon 2 Secretion is proportionate to the amount of calories consumed more calories more peptide YY 3 Inhibits the gastric motility which slows the movement of the food through the intestines to allow for absorption 4 Increases water and electrolyte absorption in the colon 5 Decreases eating C Leptin 1 Secreted by adipose cells fat cells 2 Inhibits the release of neuropeptide Y 3 Size of cells change not quantity 4 Tries to lower the levels of hunger because there is no need for energy 5 Decreases eating and increases the metabolic rate Lecture 19 March 27th I Serotonin and Satiety A Serotonin agonists consistently reduced rat food intake in a test B The rats resisted attraction of highly palatable diets during the meal less food was consumed C Associated with the shift in food preference away from fatty foods D Fenfluramine and dexfenfluramine agonists found in appetite suppressants for dieting II Theories A Set Point Theories 1 Most people attribute the motivation to eat with the presence of an energy deficit 2 Belief that we eat to bring up our energy resources back up to a optimal level energy set point B Glucostatic Theory 1 Hunger waxes and wanes as a function of blood glucose levels 2 High hunger low glucose levels C Lipostatic Model 1 Decreases in triglycerides make us want to eat and does not match up with hourly and daily hunger 2 There is not a huge decrease in body fat in one day but in a few days you can see changes D Positive Incentive Theory 1 Animals and humans are drawn to eating because of the pleasure it brings 2 The degree of hunger you feel is dependent on all the factors that affect the incentive value of eating flavors that are highly palatable E Setting Point model 1 Weight tends to drift around a natural settling point 2 Settling point is a level at which the various factors that affect body weight reach equilibrium 3 The point at which you are activated to eat changes over time and can change one s weight but body weight does tend to remain relatively constant in many adults F Weight loss 1 Weight loss occurs rapidly at the beginning 2 The amount of energy leaked is automatically reduced and the rate of weight loss becomes less and levels off 3 Then the weight gained back is rapid and you reach your normal level from before Lecture 20 April 1st I Brain Mechanisms A Original view 1 Ventromedial