Lecture 18- Eating Flashcards
What are the 2 theories of hunger?
Set point theory
Positive incentive theory
What is Set point theory (Keesey & Powley, 1986)?
-Suggests hunger is a consequence of energy deficit. As energy drops, hunger increases which initiates a meal.
-Everyone has optimal level of energy = set point
What is the inherent need to return to the set point called?
Homeostasis.
What are the 2 problem with the set point theory?
1)Evolutionary unlikely
2)Not supported by evidence
3)Ignorance of environmental factors
How is Set point theory evolutionary unlikely?
Suggests not a system that just responds to energy deficits as you need to cope with inconsistent resources in the environment.
How is set point theory not supported by evidence?
Reductions in blood glucose needed to start meal are substantial but when drinking a high calorie drink prior to mealtime it does not stop the meal.
How is set point theory ignorant of environmental factors?
Effects of learning, preference and social factors aren’t considered.
What are the 3 aspects of Positive incentive theory (Berridge, 2004)?
Anticipation
Craving
Multiple factors
What is Anticipation in positive incentive theory ?
Animals driven to eat by the expected pleasure of eating which creates positive-incentive value.
What are cravings in positive incentive theory?
Eating is initiated by craving which enables you to take advantage of good food when its available
What are the multiple factors involved in positive incentive theory?
Flavour and knowledge about the food, time since last meal
What does Woods (1991) say about when we eat?
Pre meal hunger= eating a meal stresses the body so the influx of fuel moves it away from homeostasis.
Signals for a meal evokes a cephalic phase so insulin is released into the blood.
What does wiengarten (1983) say about when we eat?
Conditioned hunger= eat more food when the conditioned stimulus was subsequently presented.
What is the ventromedial hypothalamus?
A satiety centre (inhibits eating)
What is caused by VMH lesions?
Hyperphagia (overeating)
What is caused by VMH syndrome?
1)Dynamic phase- excessive eating + weight gain
2)static phase- body weight maintained, overweight returns following diet.
What is the lateral hypothalamus?
A feeding centre
What is caused by lesions in the Lateral hypothalamus?
Aphagia (cessation of eating)
What is LH syndrome?
1)Aphagia is often accompanied by adipsia (cessation of drinking) 2)Recovery is possible eg tube feeding
Why are hypothalamus theories not backed up by research?
(3 points)
1)VMH lesions damage the PVN which produces obesity.
2)Hypothalamus regulates metabolism not eating.
3)LH lesions produce variety of motor disturbances and lack responsiveness.
What does Cannon & Washburn (1912) say about the stomach?
Contractions caused by empty stomach correlated with hunger but patients without stomachs can still get hungry.
What does Koopmans (1981) say about the stomach?
Transplanted an extra stomach and food was injected into the stomach and held there which decreased eating.
Satiety signal must have reached the brain through blood flow.
What are Peptides?
Short chains of amino acids
How are peptides released?
-Ingested food stimulates receptors in the gastrointestinal tract to release these into the bloodstream.
