appetite and eating Flashcards
(20 cards)
digestion basics
- chewing and saliva
- oesophegus
- stomach
- hydrochloric acid breaks down food
- duodenum
- absorption of nutrients in intestines
- large intestines - waste
what is the set point theory of hunger - keesey and powley
- hunger is a consequence of an energy deficit
- each individual has an optimal level of energy resources - a set point
- bodies inherently seek to return to this set point - homeostasis
what are problems with set point theory
- evolutionary unlikely - need to cope with inconsistent resources, not a system that just responds to energy deficits
- not supported by evidence - reductions in blood glucose needed to start a meal are substantial - drinking a high calorie drink prior to a meal does not stop the meal - beliefs about the content of the drink have more of an effect
- ignores environmental factors - learning, preference and social factors
what is positive incentive theory
- anticipation - animals driven to eat by the expected pleasure of eating - positive incentive value
- cravings - eating iniated by craving, may be specific, take advantage of good food
- multiple factors - flavour of food, knowledge of food
what did harris et al 1933 find about why people have a poor diet
thyamine depleted rats
- learned to choose a complete diet and avoid a thyamine deplete diet
- effect weekend when there was a choice between 10 different diets
what is pre-meal hunger - wood 1991
- eating a meal stresses the body - influx of fuel moves it away from homeostasis
- signals for a meal evokes a cephalic phase - insulin is released into blood - blood glucose decreased
- hunger isn’t a cry of energy - body preparing for homeostasis disruption
conditioned hunger in rats - weingarten 1983
- buzzer and light - food
- ate more food when CS presented
what is the ventralmedial hypothalamus
- a satiety centre - inhibits eating
what did hetherington and ranson 1940 find about the hypothalamus
lesions in ventralmedial hypothalamus led to hyperphagia - overeating and obesity
what is ventralmedial hypothalamus syndrome
- dynamic phase - excessive eating and weight gain
- static phase - body weight maintained
what is lateral hypothalamus
- a feeding centre
what did anand and brobeck say about the lateral hypothalamus
lesions in the lateral hypothalamus lead to aphagia which is cessation of eating
what is lateral hypothalamus syndrome
- aphagia is often accompanied by adipsia - cessation of drinking
why did the hypothalamus theory fail
- VMH lesions in fact damaged the PVN - this region produces hyperphagia and obesity
- hypothalamus regulates metabolism, not eating - VMH lesions increases blood insulin
- lipogenesis - production of fat
- lipolysis - breakdown of body fat
what did cannon and washburn find about the stomach
- contractions caused by empty stomach are correlated with hunger
- patients without stomachs still get hungry
- stomach is not necessary for hunger
what did koopmans find about the stomach
- transplanted an extra stomach and length of intestine into rats
- food injected into the stomach - reduction in eating
- transplanted stomach had no functioning nerves - how did they know it was full
- satiety signal must have reached brain
what are peptides
- short chains of amino acids
- ingested food stimulates receptors in the gastrointestinal tract to release these into the bloodstream
what did Gibbs, young and smith find about satiety peptide
- injected peptide choleystokinin into the gut of hungry rats. rats ate less food
- CCK may induce nausea
what is leptin
- discovered as a spontaneous genetic mutation in a mouse colony
- low leptin mice ate much more, converted calories to fat more efficiently
- suggests it’s a negative feedback signal to lower appetite appetite and encourage fat metabolism
what did seeley and woods find about leptin
- detected leptin receptors in the mouse brain
- injections of leptin in obese mice results in reduced eating and reduced weight
