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Fenster schliessen

Adiposity - negative feedback (3)

1. circulating signals (represented proporional to body fat content) inform brain about changes about body fat mass -> regulate homeostatic neurons 

2. reduction of food intake and/or increase in energy expenditure 

3. if deficient = hyperphagia (excessive eating)

Fenster schliessen

2 regions in Hypothalamus control feeding: 

 

1. VMH = satiety center (lesion -> overeating/obesity)

2. LH = feeding center (lesion -> anorexia) 

"dual center" hypothesis 

Fenster schliessen

homeostatic and reward related inputs 

- energy expenditure leads to: 

- long periods of + energy expenditure lead to: 

insulin and leptin levels go down- ghrelin levels go up

-> these responses increase rewarding properties of food + drive to eat :

1) direct effects in ventral striatum 

2) indirect effects in hypothalamus (LH) 

 

long periods: body weight reduction; 1) decrease in rewarding properties 2) increased response to satiety signals 

Fenster schliessen

AGRP neurons 

 

POMC neurons 

 

Anorexigenic neurons (3)

Orexigenic neurons (3)

1) stimulate feeding: activated by ghrelin/ inactivated by leptin and insulin 

2) reduce feeding: activated by leptin

 

A: Leptin, insulin, CCK

O: Cortisol, ghrelin, neuropeptide Y 

Fenster schliessen

Emergency circuits that stimulate feeding

as response to stressful stimuli can override the homeostatic control of energy balance 

-> Inhibition of: 

Insulin (pacreas)

Leptin (Adipose tissue)

glucose (liver)         --> increase feeding 

Fenster schliessen

Mechanisms of food reward  

VTA (origin of dopamergic cell bodies -> implicated in drug and natural reward circuitry in brain) 

LH (2)

 

-> NAc pathway may promote consumption of palatable food - involves projections to LH 

 

-> LH contains neurons that potently (mächtig) stimulate food intake + LH area neurons may also attenuate (abschwächen) response to satiety signals -> increasing the amount of food consumed during a meal 

Fenster schliessen

current causes of obesity (5)

1. Diminished physical activity 

2. disproportional food intake: lots of carbs and sugars, few proteins, fats and fibers 

3. medications

4. convenience, cheap sugar 

5. genetics 

Fenster schliessen

Defining Addiction (4)

1. Tolerance: need to increase dose over time to get the same effect

2. use regardless of consequences (physical, psychological, social) 

3. Excessive dedication to get to drugs 

4. Withdrawal