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Lecture 17

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University of Waterloo
BIOL 370
Dinu Nesan

Lecture 17: Comparative Stress Physiology - Stress: Stimuli, condition or situation that causes the loss of homeostasis (anything that disturbs homeostasis) o Action is required to minimize damage, failure to adapt results in the loss of health & development of disease (The stress response) o Acute Stress: Prey & predator, Immune response, Severe weather, Reproduction o Chronic Stress: Forestry, Landscape changes, Global warming & pollution - Stress response: Response of physiological systems to adapt to/avoid the stressor, involves the redistribution of energy usage & increase supply of energy to tissue that requires it o Inhibit unnecessary energetically expensive process o Increase energy supply to required tissue  Stressor  Changes in hormone secretory patterns  Different hormones require different times so their effects on target tissues can be observed  Catecholamines are fastest & glucocorticoids are much slower  Animal starts to show physiological consequences of the stress response  ↑ Cardiovascular tone, immune activation, energy mobilization etc. - Catecholamines: 1 wave of stress response “extreme rapid acting on all cells” o Act on G protein coupled receptors o ↑ Cardiovascular tone, energy mobilization & mental alertness - Glucocorticoids: Include cortisol (mammals) & corticosterone (rodents) “Slower action” o Keeps the catecholamines under control o Acts by changing the gene expression “differential gene expression”  Diurnal Glucocorticoid Rhythm: Trough/depression @ the middle of the night to keep energy mobilization the same as demand. Peak @ the time of arousal o Glucocorticoids binds Corticosteroid Binding Globulin (CBG)  Up to 95% of circulating Glucocorticoids are bound to CBG, bound ones cannot go across cell membrane o Glucocorticoids & Metabolism  Permissive actions that occurs before a stressor, maintained by mineralocorticoid receptors  Low level of glucocorticoids enhances mobilization of energy & ↑ blood glucose  Suppressive actions that inhibits the 1 wave response  Few suppressive actions of Glucocorticoid on metabolism, may suppress immunity, growth & reproduction 
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