Study guide, block exam 5, boil 118, Fall 2012, Dr. Benjamin Smarr. * Hunger
* Neural regulation of
* These include hormones and nutrients from the periphery that convey information about energy availability to the brain, and to the hypothalamus in particular. Neurons in distinct hypothalamic nuclei that are targeted by these molecules project to other hypothalamic nuclei as well as to extrahypothalamic sites. The complex process of regulating food intake is now known to involve the brainstem and limbic and striatal areas. This poster provides an overview of some of the molecules and circuits that are involved in the regulation of food intake and energy balance. * Hormonal regulation of
* More on these hormones http://hungerhormones.com/hypothalamus.html * Lateral Hypothalamus: This region of the brain is associated with hunger recognition. Ventromedial Hypothalamus: This nuclear region is involved with the recognition of the feeling of fullness. Paraventricular Hypothalamus: This nuclear region is involved with the regulation of hunger. Chemical Hunger: Ghrelin
The hormone ghrelin is produced by the stomach and the hypothalamus. Hormonal levels of ghrelin have been shown to increase before meals and decrease after. Ghrelin was the first discovered hunger hormone. The hypothalamus has receptors for ghrelin, which signals the body of hunger. Ghrelin has also been associated with certain aspects of certain addictive drugs, alcohol, and is associated with food cravings as a reward. Chemical Hunger: Leptin
The hormone leptin is produced by adipose (fat) tissue, and binds to certain receptors of the hypothalamus. Leptin works oppositely of ghrelin, and signals the body that it is full. Leptin also has specific roles in the regulation of energy expenditure and intake. * Anatomy of
* Gut: The gut is at the core of understanding appetite, as the image of a full belly after a meal attests. The stomach, pancreas and intestines are key players, secreting hormones to tell you to eat more or less. When you are hungry, your stomach will produce ghrelin, a hormone that encourages you to eat more. Or, once you've eaten enough, the pancreas will secrete insulin, which tells your body to eat less. These are just two of the potent cocktail of hormones that, in theory, tailor our appetite. The concept of being full - or satiated - is an important one in appetite research. Satiety is actually lack of appetite and follows eating * Brain: The gut may produce these hormones, but it's the brain that interprets the signals. Bloom says: "If we want to control appetite, we have to look both at the gut and at the brain. It's the gut that tells the brain to stop eating, but it's the brain that does the stopping. The brain, like the gut, produces its own hormones both to encourage and inhibit appetite. The hormones MCH and NPY, which are produced by the hypothalamus, can block pain signals, such as a feeling of fullness, and encourage eating. The hypothalamus also secretes melanocyte-stimulating hormones, which can slow down appetite. * Genes: The gut and brain may be working in tandem to control appetite, but our genetic make-up is crucial to whether this appetite is healthy. In some cases, eating too much - and consequently obesity - cannot be controlled by the person alone. We know that for all of us, regardless of our body weight, whether we're slim, overweight or severely obese, 40-70 per cent of our weight is determined by genetic factors. * Environment: Obesity, back in prehistoric times or even up to 30 years ago, wasn't the epidemic it is today. But if our brains, our guts and our genes haven't altered significantly in the last three decades, what's responsible for the rise in appetite? The food that we're eating has changed. Not only is our food more processed and higher-calorie, it is also easier to access than ever before, which is affecting the other...
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