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Lecture 9e - Module 37, Hunger

Lecture 9e - Module 37, Hunger - Module 37 Hunger I...

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- 1 - Module 37 Hunger I. Application of Theory #2 from Module 33: Intrinsic physiological “needs” result in “drives” (hunger, thirst and other “motivations” for behavior), which lead to “drive-reducing behaviors” (eating, drinking), which lead to “homeostasis” (a balanced internal state centered around a “set point” in body chemistry) A. Hunger is a “drive”, an “intrinsic motivation” 1. Physiology of the stomach – the hormone “ghrelin” secreted by an empty stomach 2. Physiology of the nervous system and the endocrine system, the two “information systems” of the body a. The endocrine system includes five “appetite hormones” b. The endocrine system hormones are linked to the nervous system through the hypothalamus, a section of the brain 1) Electrical stimulation of the lateral hypothalamus brings on hunger. (If the hormone insulin is high and blood glucose is low, then the stomach, intestines and liver all send electric messages through the nervous system directly to the lateral hypothalamus. The lateral hypothalamus creates the sensation of hunger.) SHOW PHOTO, p. 450 . 2) Electrical stimulation of the ventromedial hypothalamus depresses hunger. (Tumors near the base of the brain destroy the ventromedial hypothalamus; patients with such tumors eat excessively and become very overweight.) 3) The hypothalamus monitors levels of “leptin,” a protein produced by bloated fat cells. a) When researchers inject high levels of leptin into mice, the mice eat less, move more, and lose weight. b) When leptin is high, the hypothalamus speeds up the “basal metabolic rate” (the body’s resting rate of energy expenditure) – in mice, but not in humans. (Obese humans already have high levels of leptin; adding more does nothing.) 3. “Set point” is the point at which an individual’s “weight thermostat” is supposedly set. a. When the body falls below this weight, an increase in hunger and a lowered metabolic rate act to restore the lost weight.
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- 2 - b. This is good protection against a world in which there is a constant threat of famine – the history of all but the most recent times for almost all of the members of the human race. c. In societies where food is freely available, however, people become obese, and then they diet. 1) “Set point” is the reason why diets don’t work. 2) When calories go down, basal metabolism also goes down, and weight stabilizes. It won’t budge. 3) The only way to loose weight is to raise basal metabolic rate.
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Lecture 9e - Module 37, Hunger - Module 37 Hunger I...

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