Metabolism. Appetite. Hunger and satiety are regulated by a complex interaction of multiple brain centers , hormones , and sensory and motor pathways. Hunger center a region in the lateral hypothalamus that triggers the desire for food. stimulated. destroyed. Satiety center
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Hunger and satiety are regulated by a complex interaction of multiple brain centers, hormones, and sensory and motor pathways.
a region in the lateral hypothalamus that triggers the desire for food
a region in the ventromedial hypothalamus that suppresses the desire for food
The satiety center has neurons called glucostats that rapidly absorb blood glucose after a meal.
hypothesis: glucose uptake causes the satiety center to send inhibitory signals to the hunger center and thus suppresses the appetite.
Mild hunger contractions begin soon after the stomach is emptied and increase in intensity over a period of hours.
- Hormones from GI: cholecystokinin: suppressant
- Adipocytes (fat cells) secrete hormones (leptin) that regulate appetite and body weight.
(Science 299:846-849 2003)
Leptin\'s effects. Because of a gene defect, the boy doesn\'t make leptin, but treatment with the hormone, begun when he was 3.5 years old (top), brought his weight down to normal levels, as shown at age 8.
(Science 299:846-849 2003)
is the amount of energy released in the body per unit of time, expressed as kcal/hr or kcal/day
A kilocalorie (kcal) is the amount of heat that will raise the temperature of 1 kg of water by 1oC.
An average adult needs 2,000-5,000 kcal/day, depending on physical activity, mental state, and other factors such as room temperature.
1,000 Kg water x 2 - 5 C
Caloric restriction (by 30%) prolongs life span by 30%-50% and reduces morbidity of aging-related diseases.
These effects have been observed in many animal species, including worms, insects, rodents, and maybe primates.
reduced by 30%
- ATP is the universal cellular energy, and can be produced from glucose, fat, and proteins.
- A total of 38 ATP is generated per molecule of glucose in the presence of oxygen.
Blood glucose is more important than fat and proteins in providing energy
discussed in two states.
1) Absorptive State
lasts about 4 hours after a meal.
2) Postabsorptive State
Excessive glucose is stored as glycogen in the liver and muscles or as body fat.
are taken by the tissues, especially adipose and muscular tissue.
become available for protein synthesis.
Glucose is drawn from the body\'s glycogen reserves in liver and muscles, or synthesized from fats (gluconeogenesis).
After 4 to 5 days of fasting, the brain begins to use ketone bodies as supplemental fuel.
- from fat
After glycogen and fat reserves are depleted
- The body begins to burn proteins.
- The first to go is skeletal muscle proteins.
Regulation of the Postabsorptive State
- by the sympathetic nervous system and several hormones.
- The sympathoadrenal system can mobilize stored energy reserves in adipose tissue as needed.
1) glycogenolysis glycogen glucose
2) gluconeogenesis AA/FFA glucose
3) lipolysis triglyceride FFA
- At rest, mainly generated in brain, liver, heart, endocrine glands, and skeletal muscles(20-30%).
- During vigorous exercise, skeletal muscles produce 30-40 times as much heat as the rest of the body.
The body loses heat through:
in the hypothalamus
Exposure to excessive heat causes:
below 24oC (75oF) = fatal.