Neural Mechanisms in Eating Behaviour

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  • Created by: Emilyio
  • Created on: 16-04-16 20:44
(A01) What does Satiery mean?
It is the satisfaction of hunger, or the completion of eating to pleasing levels.
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(A01) What is Homeostasis?
The mechanisms that DETECT the state of the internal environment as well as CORRECT the situation to retore said environment to its optimal state.
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(A01) What's the issue with the Homeostasis process?
There's a significant issue with time lag between mechanisms restoing equilibrium and the body registering the effect. By the time the person's eaten enough for energy, only a little food has been digested and so receptors has insufficient 'data'.
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(A01) What's this 'data' needed for?
It's to 'turn off' eating through the triggering of receptors taht are responsible for detecting the humans nutrient levels
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(A01) Which part of the brain 'turns eating on'?
The Lateral Hypothalamus (LH)
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(A01) How is the Lateral Hypothalamus activated?
A decrease in glucose levels in the blood activates the LH, creating hunger and leading the individual to search for, and consume, food - leading to an increase in Glucose levels again.
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(A01) What part of the brain 'turns eating off'?
The Ventromedial Hypothalamus (VMH)
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(A01) How is the VMH activated?
The rise iun glcose levels when a person eats leads to feelings of satiation. This inhibits futher feeding.
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(A01)Lateral Hypothalamus - What is aphagia?
The refusal, or inability to eat as a result of damage to the LH
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(A01) Lateral Hypothalamus -How was Aphagia discovered?
in 1950's, hypothalamus research in eating behaviour in rats.
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(A01) Lateral Hypothalamus -What is Neuropeptide Y?
A neurotransmitter found in te hypothalums. It's important for turning on eating.
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(A01) VMH -What are ob/ob mice?
Mice that have 2 copies of the gene for obesity (abbreviated ob). Such mice have a tendency to overeat, especially in foods that are higher in fat or sugar.
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(A01) VMH-(Leptin & Obesity) - Zhange et al 1994
Discovered ob/ob mice have defective genes for the protein Leptin. Injecting ob/ob rats with leptin causing dramatic weight loss.
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(A01) Lateral Hypothalamus - Wickens et al 2000
found that when neuropeptite Y was injected into rats, they immediately began feeding, even if satiated.
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(A01) Lateral Hypothalamus - Stanley et al 1986
Repeated injection of N-Y into rats. They reached obesity in just a few days.
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(A01) Ventromedial Hypothalamus - What is Hyperphagia?
A condition of overeating through excessive desire for food.
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(A01) Ventromedial Hypothalamus - What did researchers find about damage to the VH?
That it caused rats to overeat and lead to a condition called Hyperphagia.
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(A01) Ventromedial Hypothalamus -What else did researchers find about the VMH?
That it also inhibits feeding, indicating that this is the 'off switch' for when satiety is reached.
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(A01) Ventromedial Hypothalamus -Gold 1973 -
Found damage to the nerve fibres passing through the VMH tends to damage another area of the hypothalamus, the Paraventricular nucleus (PVN). It is now thought that damage to the PVN alone causes hyperphagia.
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(A01) Ventromedial Hypothalamus - What else is thought that the PVN does?
It also detects the specific foods our body needs, and consequently seems to be responsible for many of our cravings.
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(A01) Neural Control - What does the cognitive aspect of food include?
Images of food from memory as well as food related smells and sights ( ie-walking past a restaurant).
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(A01) What 2 areas originate neural control of cognitive factors in hunger?
The Amydala and the Inferior Prefrontal Cortex
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(A01) What's the role of Amygdala?
Primarily selection of foods based on previous experience.
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(A01) Amygdala - Rolls & Rolls 1973 -
Found surgically removing the amygdalala in rats would cause them to consume familiar and novel food, whereas amygdala-intact rats would avoid novel foods.
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(A01) Where does the inferior frontal cortex get its mesages?
The olfactory bulb
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(A01) What's the olfactory bulb?
The part of the brain responsible for smell.
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(A01) Inferior Frontal Cortex - Kolb & Whishaw 2006 -
Because odours influences the taste of foodsm damage to the inferior prefrontal cortex is thought to decrease eating because of diminished sensory responses to food odour, and also probably taste.
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(A02) Limitations of homeostasis as an exmplantion -
For a hunger mechanism to be adaptive and prevent energy deficits, not jsut react to them. The processes involved are incompatible in the reality of which such systems would've evolved.
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(A02) What would need to have occurred for a homeostatic mechanism to be adaptive
It must promote levels of consumption that maintain bodily resources well above the optimal level to act as a buffer against future lack of foof availability.
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(A02) Simplified explanation for damage to LH
Damage to the LH caused deficits in other aspects of behaviour (thirst & sex) rather tha just hunger. As well as this, research has shown EB is controlled by neural circuits that run through the brain, not just hypothalamus.
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(A02) Simplified explanation for damage to LH - Sakurai et al 1998
Although the LH plays an important role in controlling eating behaviour, it is not, as previously thought, the brains 'eating centre'.
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(A02) Neuropeptide Y - Marie et al 2005
Genetically maniuplated mice so they did not make NPY. They found no subsequent decrease in their feeding behaviour.
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(A02) What does Marie et al 2005 suggest?
The hunger stimulated by injections of NPY may actually be an experimental artefact, in the flood of NPY in manipulations caused by normal amounts.
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(A02) VH - Gold 1973
found that lesions restricted to the VMH alpne did NOT result in hyperphagia and only produced overeating when they included other areas, such as the paraventrivular nucleus.
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(A02) Line of argument against Gold 1973
Most studies show that, compared to lesions in other brain areas such as PVN, animals with VMH lesions ate much more and gained much more.
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(A02) Neural control - Klüver-Bucy syndrome
Patients with this syndrome typically showed increased in appetite, indiscriminate eating and even attempt of eating non-food items. - food cues no longer represent accurately real world value to individual.
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(A02) Zald & Pardo 1997
provided physiological evidence to support the claim that the amydala participates in the emotional processing of olfactory stimuli. They exposed healthy adult pp's to aversive olfactory stimuli when measuring blood flow to amygdala by PET scan.
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(A02) Zald & Pardo 1997 - Findings
They found exposure to unpleasant odours produced significant blood flow increases blood flow. Increased blood flow to amygdala was associated with subjective ratings of the percieved unpleasantness of the stimuli.
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(A02) Lutter et al 2008
Dallas, Texas - shows that the body produces extra quanitites of the hormone Ghrelin in response to stress - natural stress response. However, it boost appetite. This suggests that blocking Ghrelin, reduces comfort-eating. Yet it will reduce benefits
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(IDA) - Real World Application - Yang et al 2008
Canada - shown that NPY is produced by abdominal fat. This leads to a vicious circle of more eating and more fat cells. By targeting at-risk of NPY people could be treated with drugs.
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(IDA) Evolutionary Approach
Evolutionary theorists suggest that the primary stimulusfor hunger and eating is food's positive-incentive value - people eat because they enjoy it and enjoy food thought to enhance our ancestrals survival.
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Card 2

Front

The mechanisms that DETECT the state of the internal environment as well as CORRECT the situation to retore said environment to its optimal state.

Back

(A01) What is Homeostasis?

Card 3

Front

There's a significant issue with time lag between mechanisms restoing equilibrium and the body registering the effect. By the time the person's eaten enough for energy, only a little food has been digested and so receptors has insufficient 'data'.

Back

Preview of the back of card 3

Card 4

Front

It's to 'turn off' eating through the triggering of receptors taht are responsible for detecting the humans nutrient levels

Back

Preview of the back of card 4

Card 5

Front

The Lateral Hypothalamus (LH)

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