eating and appetite Flashcards
(23 cards)
How does digestion occur?
-30ft coiled meat tube
-Goes in through the parotid gland
-Goes out through anus
What are the two theories of hunger?
-Set Point Theory (Keesey and Powley, 1986)
-Positive Incentive Theory (Berridge, 2004)
Describe Set Point Theory
-Hunger is consequence of energy deficit
-Everyone has optimal level of energy resources = set point
-We seek to return to this set point = homeostasis
What are the issues with Set Point Theory?
-Evolutionarily unlikely
-Not supported by evidence
-Ignorance of environmental factors
What is meant by evolutionary unlikely?
-Need to cope with inconsistent resources in environment, rather than a system that just responds to energy deficits
How is it not supported by evidence?
-Drinking high calories drink prior to meal time doesn’t stop you needing a meal
-Reduction in blood glucose level needed to start a meal is substantial
Why does it ignore environmental factors?
-Effects of learning, preference and social factors
Describe Positive Incentive Theory
-Anticipation = animals driven to eat by expected pleasure of eating = positive incentive value
-Craving = eating initiated by craving, may be for something specific
-Multiple factors = flavour, knowledge, time since last meal, amount of food in gut, blood glucose
What was found to do with learned preferences and aversions?
-If rats were given glucose flavour or nothing flavour = they chose glucose = conditioned taste preference
-If rats were given LiCl flavour or nothing favour = they chose nothing = conditioned taste aversion
How can food be socially acquired (Galef, 1995)
-Animals will prefer a certain type of food if they’ve seen another animal eating it
-Evolutionary advantage
What was found to do with learning to eat vitamins and minerals?
-Associating salt with flavours (Fudim, 1978)
-Artificial flavourings
-Almond and Salt = No injection = Preferred banana over almond
-Banana and Sugar = Formalin injection = Preferred almond over banana
What initiates a meal?
-Pre meal hunger (Woods, 1991)
-Eating stresses the body = moves away from homeostasis
-Signals for a meal = evokes cephalic phase, where the body is preparing itself for food
-Conditioned hunger in rats (Weingarten, 1983)
-E.g. eat more food when a buzzer and light are turned on
What physiological research was conducted to do with the ventralmedial hypothalamus?
-Hetherington and Ranson (1940) looked into VMH syndrome
1: Dynamic phase = excessive eating and weight gain
2: Static phase = body weight maintained
What physiological research was conducted to do with the lateral hypothalamus?
-Anand and Brobeck (1951) looked into LH syndrome
-Lesion = aphagia
1: Aphagia is often accompanied by adipsia
2: Recover possible = tube feeding, dry food pellets etc.
What is aphagia?
-Cessation of eating
What is adipsia?
-Cessation of drinking
Why could these theories be wrong?
1: VMH lesions damaged the PVN = produces hyperphagia and obesity
2: Hypothalamus regulates metabolism, not eating
3: LH lesions produce motor disturbances and lack responsiveness
What physiological research has been done in regards to the stomach?
-Cannon and Washburn (1912)
-Contractions caused by empty stomach correlated with hunger
-Patients without stomach still get hungry
What did Koopmans (1981) find in regards to the stomach?
-Transplated extra stomach and length of intestine into rats
-Food injected into stomach = decreased eating
-Transplanted stomach has no functioning nerves
What physiological research was conducted in regards to peptides?
-Short chain of amino acids
-Ingested food = stimulates receptors in gastrointestinal tract = released into bloodstream
What did Gibbs, Young and Smith (1973) find to do with peptides?
-Injected peptide cholecystokinin (CCK) into gut of hungry rats
-Rats ate less food
-CCK may induce illness
What is leptin?
-Discovered as spontaneous genetic mutation in mouse colony
-Low leptin mice ate more = converted calories to fat more efficiently
-Negative feedback signal = encourages fat metabolism
What did Seeley and Woods (2003) find in regards to leptin?
