EATING AND HOMEOSTASIS – principal factors and ...
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
- animals initiate 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 ( temp declines 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
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