Chapter 6 Motivation and Regulation of Internal States Pages 162 171 Contributes to dietary selection in three additional ways 1 Sensory specific satiety the more of a specific food a person eats the less appealing the food becomes Encourages a varied diet balanced diet It is controlled by the Nucleus of the Solitary Tract NST in the medulla Learning in a reflexive fashion 2 Learned taste aversions the avoidance of foods associated with illness or poor nutrition Get sick one time can t even think of it without feeling nauseous Help prevent toxins entering the body from food evolution May be one reason chemotherapy patients loose appetite 3 Learned taste preferences preference for flavor of foods that contain important nutrient s e g Vitamin B Ex over time rats will like certain foods that have vitamin injected over the food with no vitamin Animals learn to prefer the flavor of a food enriched with thiamine presumably makes them feel better The Digestive Process Begins with saliva in mouth enzymes Hydrochloric acid and pepsin in stomach If food irritates stomach regurgitation occurs If no irritation occurs toxins reach the area postrema of brain induce projectile vomiting Most digestion occurs in small intestine esp duodenum Carbohydrates glucose Proteins amino acids Fats fatty acids and glycerol These are transferred to liver via the hepatic portal vein and then to the rest of the body What s left goes to the large intestine water recycling system reabsorbs water The two phases of feeding cycle Absorptive phase Glucose increases parasympathetic activation pancreas secretes insulin glucose enters body cells glucose stored in liver and muscles as glycogen fat stored in adipose cells as triglycerides Body wants to store as much as possible during feasting phase because it might not have that later Fasting phase Glucose decreases sympathetic activation pancreas secretes glucagon glycogen transformed to glucose for brain stored fat released as fatty acids for body and glycerol for brain after conversion to glucose Used in body when little food is available to power the body Two major signals for hunger Glucoprivic hunger deficit in glucose Lipoprivic hunger deficit in fatty acids Low glucose and fatty acids signaled via vagus nerve to the Nucleus of the Solitary Tract NST and the area postrema both in the medulla Info is then relayed to the Arcuate Nucleus AN hypothalamus ParaVentricular Nucleus PVN and Lateral Hypothalamus LH hypothalamus increase in release of neuropeptide Y in LH and PVN Powerful stimulant for eating and reducing metabolism general body activity and even sexual motivation Another powerful stimulant for eating Ghrelin produced by stomach dumped into blood stream affects AN which then affects the PVN and LH causing you to become hungry Signals that end eating Stretch receptors in stomach if stretched too far by food signal sent signal via vagus nerve to medulla NST and area postrema decrease of neuropeptide Y in PVN and LH Cholecystokinin CCK peptide hormone released when food passes through the duodenum vagus nerve medulla decrease of neuropeptide Y in PVN and LH Peptide YY3 36 PYY intestine secreted hormone reaches Arcuate Nucleus through bloodstream slower action than CCK High levels of nutrients in blood detected by liver vagus nerve medulla NST and area postrema decrease of neuropeptide Y in PVH and LH So many pathways make treating overeating complicated Long term regulation of body fat Leptin hormone secreted by fat cells Amount of leptin in blood is proportional to of body fat more fat more leptin Increased leptin in blood decrease in neuropeptide Y in PVN and LH Decreased leptin in blood increase in neuropeptide Y in PVN and LH Leptin levels are about 4 times higher in obese than non obese individuals may have fewer active leptin receptors in PVN and LH Chapter 7 Biology of Sex Pages 190 193 Is sex a physiological drive like hunger thirst Main difference sex is not essential for survival of individual hunger and thirst take precedence over sex Similarities Arousal and satiation Roles of hormones Involvement of specific brain areas Phases of the sexual response cycle Master and Johnson 1966 Excitement plateau orgasm resolution orgasm to resolution refractory phase sensory specific satiety There are individual differences based on different individuals such as how long plateau is Males must go back to base before becoming sexually aroused again must obey refractory phase not necessarily true for females Sensory specific satiety the more of a specific food a person eats the less appealing the food becomes encourages a varied diet Coolidge Effect quicker return to sexual arousal for a male when a new female is introduced Named after former president Calvin Coolidge legend observing chickens wife points out that cock mates all the time husband points out that it s not with the same female every time Fairly common phenomenon amongst species even humans better chance of passing genes on to new generation when mating with multiple females Females don t stuck with gestation cheap sperms expensive eggs theory A male can potentially have a large number of children quickly by mating with different females more of his genes passed to the next generation Selfish Gene theory R A Dawkins 1976 Role of Hormones on Sexual Activity Sex hormones Androgen male characteristics and functions Testosterone major sex hormone in males turns embryo male Most research done is on testosterone seems to have more of an effect Estrogen female characteristics and functions Testosterone and Sexual Activity Evidence from castration removal of the gonads studies Sexual behavior decreases Testosterone appears necessary for male sexual behaviors but amount required is minimal Can be produced from adrenal cortical glands sexual drive not completely gone but not as strong as before Females initiate sex more at midcycle when both estrogen and testosterone levels are increased Testosterone may be more important than estrogen for this in women Testosterone increases as a result of sexual activity in both males and females Cause effect relationship between testosterone and sexual activity is still unclear