When physiological homeostasis fails behavioral

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When physiological homeostasis fails, behavioral maintenance is often possible--appetite changes. (recall behavioral regulation of temperature in Iguannas). Specific hungers…
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Sodium Preference/Balance Sodium Intake Methodology Animal gets a choice between different tubes. In most preference tests there are just 2 tubes. In this case, the animal has a choice between water and normal saline (0.85%). Fluid intake is measured daily and a preference is calculated. In this example, sodium is preferred over straight water by 67% (20/30). The preference threshold is the concentration at which preference over water exists. Detection threshold is the concentration at which the animal can tell the difference. These two parameters are not identical.
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Adrenalectomy & Salt balance Adrenalectomized rats usually die within one week. If salt water or salt is offered to the animal, they survive as well as intact rats. Before adrenalectomy the animal drinks very little salt. Afterwards, salt intake increases dramatically.
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Salt is frequently a defended resource among animals in the wild. B-W and colleagues studied bunnies (marsupials too) that ranged over several types of habitats. Snowy mountains (where the vegetation is naturally low in sodium) Desert (or seashore) (where the plants have high levels of salt). Observed morphological, physiological, and behavioral changes based on habitat Blair-West et al., 1968 study
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Blair-West et al., 1968 study Snowy Mountain Rabbits Hypertrophied zona glomerulosa of the adrenal cortex. Aldosterone concentrations were high Aldosterone conserves salt. Urinary sodium content was very low (undetected) Voracious sodium appetite Desert Rabbits Narrow z. glomerulosa Low blood aldosterone High urinary concentrations of sodium No salt appetite. When observed at low magnification (left) the capsule (A), cortex (B), and medulla (C) are visible. At higher magnifications (right) the divisions of the cortex are visible: Zona glomerulosa - zg -with cells in small clusters which secrete aldosterone , Zona fasciculata - zf -
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