EATING AND HOMEOSTASIS – principal factors and hypothalamic regions that control feeding

Homeostasis - processes that regulate behaviors like energy intake in the form of food and energy expenditure in the form of cellular metabolism/exercise (these two processes are coupled over intervals resulting in stable body fat stores)

- we behave as though we have a set point for body weight

- apparent energy regulation area in the ventromedial nucleus of hypothalamus (VMH) and lateral nucleus of hypothalamus (LH); consequences of activity in this region involve multiple mechanism, including changes in activity, metabolism, motivation, and sensation

- VMH is satiety center, LH is feeding center

- lesions of LH  animals do not eat and may starve to death unless force-fed

- lesions of hypothalamus (VMH)hyperphagia (overeating)increased insulin secretion obesity

- obesity may have other causes: adipocytes release OB protein enters brain  provides feedback of amount of body fat present  brain induced to alter release of hormones related to metabolism and influence particular behaviors related to eating/general activity levels

- OB protein may have binding sites in satiety area of hypothalamus

- activation of sympathetic nervous system accelerate metabolism of fat and alter OB protein production

- lesions of the amygdala cause hyperphagia

- eating occurs in distinct events (meals)

- vertebrates store excess caloric energy when ample food available and draw on those reserves when food is not available

- organisms live off recently ingested energy during and immediately after meals (storing excess to support bodily activities unit it eats again)

- the supply of energy in the blood does not decrease to anywhere near the threshold necessary to trigger eating

- animalsinitiate meals even though abundant energy is readily available

- small fluctuations of glucose provide important signals that the brain uses to help determine when eating should be initiated

- the liver responds to small fluctuations of fatty acids by sending signals to the brain via the vagus (X) nerve

- Cholecystokinin is released from the small intestine in response to feeding; it inhibits or suppresses feeding with a slow onset

- prior to spontaneous mealsbody temperature increases when meal beings, temperature continues to increasetempdeclines as meal is terminated

- metabolic rate decreases prior to start of spontaneous meals and increases as eating begins

- the less you eat  the longer you live