eating and appetite Flashcards
eating and digestion, theories of hunger, eating factors, physiological research - hypothalamus, physiological research - stomach, physiological research - peptides (31 cards)
what is digestion?
chew food and mix with saliva
food squeezed in oesophagus
stomach stores food and uses hydrochloric acid to break down protein molecules into amino acids
upper part of intestine where majority from waste in large intestine
food then ejected
what is the set point theory?
Keesey and Powley (1986)
hunger is 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
as energy levels drop, hunger increases and a meal is initiated
what are the problems of the set point theory?
evolutionary unlikely - need to cope with inconsistent resources in the environment, not a system that just responds to energy deficits
not supported by evidence - reduction in blood glucose needed to start a meal are substantial, drinking a high calorie drink prior to meal time does not stop meal, beliefs about the content of the drink has more effect (Lowe, 1993)
ignorance of environmental factors - effects of learning, preferences and social factors
what is the positive incentive theory?
Berridge (2004)
anticipation
craving
multiple factors (flavour of the food, knowledge about the food - learning, time since last meal, amount of food in gut, blood glucose levels
what is anticipation (Berridge, 2004)?
animals driven to eat by expected pleasure of eating
expected pleasure = positive-incentive value
what is craving (Berridge, 2004)?
eating (and the perception of hunger) is initiated by craving
may be for something specific
enables you to take advantage of good food (when its available)
how do we decide what to eat?
learned taste preferences and aversions
food preferences can be socially acquired
learns to eat vitamins and minerals
what are learned taste preferences and aversions?
conditioned taste preference
conditioned taste aversion
what is conditioned taste preference?
rats
neutral flavour into a drinking tube
one (flavour A) has nutritional value - mixed with glucose
at test, flavours no longer mixed with glucose
still prefer flavour A even though it has no nutritional value
what is conditioned taste aversion?
pair one flavour with LiCl
LiCl causes the rats to feel sick
still neutral flavours
rats avoid flavour that was previously paired with LiCl
how can food preferences be socially acquired?
animals prefer certain type of food if they’ve seen other animals eating it
clear evolutionary advantage (poison/death)
what was Fudim’s (1978) experiment into associating salt with flavours?
rats can freely eat both mixtures
injection of formalin (prompts a salt craving) vs control (nothing)
control = prefer banana (previously paired with sugar - tasty)
formalin = prefer almond (previously paired with salt
why do some people have such a poor diet?
Harris et al (1933)
thyamine (vitamin B1) depleted rats
learned to choose a complete diet and avoid a thyamine deplete diet
effect weakened when there was a choice between ten different diets
what initiates a meal?
pre-meal hunger (Woods, 1991)
conditioned hunger in rats (Weingarten, 1983)
how does pre-meal hunger initiate a meal?
Woods (1991)
eating a meal stresses the body - influx of fuel moves it away from homeostasis
signals for a meal (e.g. time of day, smells) evokes a cephalic phase - insulin released into blood - lowers blood glucose
hunger isn’t cry for energy - body preparing for homeostasis disruption
what did Weingarten (1983) find about conditioned hunger in rats?
buzzer and light (CS) -> food
rats ate more food subsequently when CS was subsequently presented
what role does the ventralmedial hypothalamus play in hunger?
a satiety centre (inhibits eating)
what did Hetherington and Ranson (1940) find about the ventralmedial hypothalamus?
VMH lesions = hyperphagia (overating and obesity)
what is VMH syndrome?
dynamic phase - excessive eating, weight gain
static phase - body weight maintained, overweight state returns following diet
VMH syndrome rats won’t work for food
sensitive to unpalatable foods (finnicky)
what role does the lateral hypothalamus play in hunger?
feeding centre
what did Anand and Brobeck (1951) find about the lateral hypothalamus?
lesion = aphagia (cessation of eating)
what is LH syndrome?
Teitelbaum and Epstein (1962)
aphagia is often accompanied by adipsia (cessation of drinking)
is recovery possible from LH syndrome?
yes
tube feeding
milk soaked cookies
dry food pellets
how did the hypothalamus theory crumble?
VMH lesions in fact damaged paraventricular nucleus - this region produces hyperphagia and obesity
hypothalamus regulates metabolism, not eating - VMH lesions increase blood insulin (increase lipogenesis = production of fat, decrease lipolysis = breakdown of body fat) so rats must consume more calories to meet demands
LH lesions produce variety of motor disturbance and lack of responsiveness
