Chapter 16.docx

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21 Apr 2012
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Chapter 16
The HT, homeostasis and motivated behavior
The Ht plays important roles in body temp, fluid balance and energy balance
A response occurs when there is an imbalance in homeostasis
1. Humoral response: appropriate pituitary hormones released into blood
2. Visceromotor: ANS outputs adjusted accordingly
3. Somatic motor: somatic motor behavioral response
The long term regulation of feeding behavior
We eat to maintain energy at a certain level (below which cell death and organism death will occur)
Energy balance
Prandial state: After we eat, we are in a prandial state (blood is filled w/ nutrients). There are two
types of energy storage macromolecules assembled by anabolic metabolism, glycogen (finite
reserves in liver and skeletal muscle) and triglycerides (stored by adipose tissue).
Postabsorptive state: Catabolism breaks down the complex macromolecules into simpler nutrients
for cellular respiration. Glucose is used by all cells, and fatty acids and ketones are needed for non-
neurons
We must have a balance between catabolism and anabolism. Too much intake= adiposity increases=
obesity. Catabolism > anabolism = adiposity decreases = starvation.
Hormonal and ht regulation of body fat and feeding
Neurons in periventricular zone detect decrease in release of fat cell protein, and neurons in lateral
hypothalamus will induce feeding behavior
Body fat and food consumption
o Lipostatic hypothesis: the brain has a set point for adiposity that will incite defensive
behavior if there are alterations (too much eating= reduce adiposity and vice versa)
o Coleman: found that obese mice lacked ob/ ob gene in their DNA. When parabiosed (fused)
with normal mice, their adiposity decreased.
o Friedman: found leptin to the protein that is released by adipose tissue that acts directly on
ht neurons that decrease appetite and increase energy expenditure
Hypothalamus and feeding
o Hetherington and Ranson: found that lesions in hypothalamus cause obesity/ starvation
Lateral hypothalamus (lateral hypothalamic syndrome): caused by damage to LHT,
causes loss in appetite (anorexia)
Ventromedial hypothalamus (ventromedial hypothalamic syndrome): caused by
damage to VHT, causes obesity
Effects of elevated leptin on HT
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