4b. Neural Mechanisms in eating

Neural Mechanisms in eating and satiation : 

Neural Mechanisms in eating and satiation Hunger = the body signalling need for nutrients and energy Satiation = body signalling satisfaction of need for nutrients and energy.

How hunger and satiation work : 

How hunger and satiation work Homeostasis: Detect what’s happening inside the body Correct an unstable environment within the body.

Slide 3: 

Time lag: You don’t stop eating until body has what it needs Glucose levels Activate lateral hypothalamus Glucose levels Activate ventromedial hypothalamus satiation Eat Hunger

Role of neural mechanisms: Lateral hypothalamus : 

Role of neural mechanisms: Lateral hypothalamus When damaged in rats = “aphagia” = no urge to eat When stimulated, it elicits eating. This is the “on” switch for eating and is related the neurotransmitter “neuropeptide Y”(NPY). Rats injected with this = immediate feeding behaviour, even when satiated (Wickens 2000) Repeated injection of NPY = obesity in rats (Stanely et al)

The ventromedial hypothalamus & other areas involved in eating : 

The ventromedial hypothalamus & other areas involved in eating Damage here = overeating in rats = hyperphagia Stimulation of this = inhibited feeding But research has found that when the ventromedial hypothalamus in damaged, another area of the hypothalamus, the paraventricular nucleus is also damaged. Gold said that when the paraventricular nucleus is damaged, this alone leads to overeating/hyperphagia and is responsible for our cravings.

Neural control of cognitive factors : 

Neural control of cognitive factors Amygdala and inferior prefrontal cortex are involved in our thoughts about food, hence the reason why when we think of food, we want to eat it. The amygdala helps us select our food on the basis of previous experience. Rolls & Rolls: If we remove this in rats, they consume both old and new foods indiscriminately, whereas rats whose amygdala wasn’t removed, chose only familiar foods. Inferior frontal cortex: Receives message from olfactory bulb (smell area in brain)-Smell is connected to taste buds. If damaged = less eating because less taste (Kold & Whishaw)

Slide 7: 

Watcha looking at?! Don’t judge me…it’s the damned LEPTIN! Some mice have 2 copies of the obesity gene “ob/ob”. This makes these mice overeat, especially food high in sugar and fat. Zhang et al: For normal mice, the ob/ob gene is for the protein leptin which travels in the blood stream and causes fat loss and decreased appetite. In obese mice, the ob/ob gene for leptin is DEFECTIVE = bingeing mouse!

Applying your learning : 

Applying your learning Neural mechanisms in eating and satiation can be used to explain why people get fat or even obese…explain what they say (and help the world rid itself of obesity so that no more cats have to suffer in cartoons!!!)