Homeostasis – “maintaining of a constant internal environment”
Neural and hormonal mechanisms in eating
· Food intake is controlled by a complex neural system – in order to receive nutrients and necessary energy supplies.
· Hypothalamus plays a key role in regulation
- Endocrine system is connected to the hypothalamus, chemical messages are secreted called hormones –hypothalamus controls the secretion
· In response to stimulation
-Lateral hypothalamus (LH) Produces feeling of hunger, if this is damaged, can result in dramatic reduction in food intake.
Hoebal et al (1966) found that damage to the LH causes loss of appetite and self-starvation.
Case study – small sample size, unreliable.
- Ventromedial hypothalamus (VMH) Triggers sense of feeling full, reducing appetite – is referred to as the satiety centre.
Anand and Brobeck (1952) found that lesions in the LH of rats led to a loss of feeding, as well as showing stimulation in LH in rat’s produces feeding and lesions to the VMH in rat’s leads to obesity.
Animals – Human eating behaviour is also influenced by non-biological factors such as culture, social and health concerns.
· Increase in peptide neurotransmitter neuropeptide (NPY) increased levels of this in the paraventricular nucleus increase food intake and weight.
- This releases leptin, released from fatty cells.
· Also the stomach releases a hormone called ghrelin when it is empty – High levels of ghrelin also stimulate the LH.
Cummings et al (2004) provided support for the role of ghrelin. Ghrelin levels of 6 males who were monitored every 5 minutes between their midday meal and when they requested their evening meal. As well as assessing their hunger levels. Ghrelin levels fell after eating lunch and peaked at time of requesting their main meal.
Sample size was small – hard to generalise
Just male pps – gender bias
Correlation – no cause and effect
· Reductionist, ignores psychological cultural and social factors
· Lots of evidence involve animals; caution to be taken with reliability of results.
LH = produces feeling of hunger
VMH = Gives us the feeling of being full up
Ghrelin = hormone when stomach is empty
Evolutionary explanations of Food Preference
Human evolution – Evolutionary psychologists have suggested that all humans have evolved through a process of natural selection and that only those characteristics that confer an advantage or at least do not confer a disadvantage, survive as the species evolve.
Born with a genetic predisposition for basic treats and that these influence food preference.
Innate food preferences:
sweet foods- provide important calories for energy e.g. in fruit there is natural fructose
The tongue has sweetness receptors.
Desor et al (1973) did a study into the facial expressions of suckling babies; they found that sweet foods were shown as a preferred taste.
Salty Foods – Infants about 4 months old showed a mark preference for salty foods over non salty.
Denton (1982) used mainly animals in…