mancatul Flashcards
Why do we eat?
To supply the body with energy that we need to survive.
Food is enjoyable
To socialise - there is bonding when socialisation happens around food
What are the 3 forms that energy is available in?
Immediate use (when we need fuel) -
1. glucose (simple sugar)
Short- and long-term reservoirs -
2. amino acids (broken down from proteins)
3. lipids (fats)
What are the structures involved in the control of eating?
The gut-brain axis which links the brain and the digestive system
What controls eating?
- Chemical messengers
- Neural and cognitive factors
- Social and environmental factors
What are the chemicals regulating hunger or satiety?
Hunger: ghrelin
Satiety: leptin, PYY, insulin
What is the network of interacting brain regions that controls eating?
Cortex
Hypothalamus
Brainstem
What is the role of the cortex in neural control of eating?
Cortex is involved in taste perception and food appreciation.
What is the role of the orbitofrontal cortex (OFC, part of prefrontal cortex)?
It is linked to encoding of reward value of food
What is the role of the hypothalamus in the neural control of eating?
The arcuate nucleus contains receptors of ghrelin, leptin, insulin and serotonin.
What are the regions of the arcuate nucleus?
Lateral hypothalamic area LHA - hunger centre
Ventromedial nuclei VMN: satiety centre
What is ghrelin?
A hormone secreted from the stomach when it is empty.
Signals hunger
High before meals
Decreased after meals
Also linked with some parts of the brain engaged in reward processing.
What signals satiety? (stomach)
Stomach contains nutrient receptors.
An animal will keep eating if food does not get to the stomach.
Stomach detects nutrients not volume
What signals satiety? (Intestine)
Intestine
1. CCK - a hormone secreted in part of the intestine and involved in breaking down fats
CCK release is triggered by food in the gut and this sends a satiety message to the brain (hypothalamus)
- PYY - released after a meal, in proportion to the calories ingested
What signals satiety? (liver and pancreas)
Liver and pancreas
Signals to the brain that food and nutrients have been digested
Also leptin is realised by fat tissue as satiety signal
More leptin - less appetite
What happens if the lateral hypothalamus LH is lesioned?
If lesioned an animal will lose interest in food.
If stimulated an animal will be overeating.
What happens if the ventromedial hypothalamus is lesioned?
If lesioned an animal will overeat.
If stimulated an animal will lose interest in food.
What is an issue with saying that lateral hypothalamus is the centre of hunger?
If lesioned, eating recovers voluntary despite no recovery of the LHA.
This would not happen if hunger was the centre
If stimulated, besides overeating other behaviours happen (running). LH might be involved in arousal rather than eating.
What is an issue with saying that ventromedial hypothalamus is the centre of satiety?
Lesions to the VMH alone do not cause overeating.
Overeating involves lesion to VMH and other areas.
What is the set-point theory?
Individuals engage in eating behaviour to maintain internal homeostasis (a stable, constant internal state).
If energy levels are below target - we eat
If target is reached - we stop eating
What is the system trying to maintain?
Glucose levels (glucostatic set-point theory): which may regulate day to day eating
Body fat levels (lipostatic set-point theory): which may regulate long-term weight
What is evidence to support set-point theory?
Glucoprivation and lipoprivation can be experimentally induced and will stimulate eating up to when the set-point is reached, supporting set-point theory.
What is evidence against set-point theory?
We eat even when glucose levels are high
In everyday life drops in glucose and fat levels are not enough to induce eating
What is eating as conditioning?
Just seeing food can make us hungry.
What is eating as habituation?
When we eat the same food for a long time, being presented with another option is tempting.
What is sensory specific satiety?
Satiety is specific to the taste of food recently digested – we get full faster if meals are limited to one food type
Variety of food increases meal size
What are the advantages and disadvantages of eating as habituation?
Advantages:
-encouraged to have variety in our diet
-reduces the possible accumulation of toxin that may be in a food
Disadvantages:
-may contribute to weight increase
What are the negative effects of eating with others?
Increased meal size in social situations.
Researchers found a positive relationship between amount of food eaten and number of people present.
What are the positive effects of eating with others?
Sharing food promotes cooperative skills.
Those who shared plates showed greater cooperation.
