Physiological Bases of Stress and Adaptation Dr Paola

Physiological Bases of Stress and Adaptation Dr. Paola S. Timiras

Origin and Evolution of Stress • Claude Bernard (1813 -1878) – Leçons sur les phénomènes de la vie communs aux animaux et aux végétaux – Constancy of the internal environment • Walter Cannon (1871 -1945) – The Wisdom of the Body – Homeostasis, stress, autonomic (sympathetic) nervous system • Hans Selye (1907 -1982) – The Physiology and Pathology of Stress; a Treatise Based on the Concepts of the General-Adaptation-Syndrome and the Diseases of Adaptation – Alarm reaction, adaptation, exhaustion – Hypothalamo-pituitary-adrenocortical axis (HPA)

Origin and Evolution of Stress • Robert Sapolsky – Stress, the Aging Brain, and the Mechanisms of Neuron Death – Why Zebras Don’t Get Ulcers: an Updated guide to Stress, Stress-Related Diseases, and Coping – Role of limbic system (hippocampus) in regulation of HPA • Bruce Mc. Ewen & Theresa E. Seaman – The End of Stress as We Know It – Allostasis, homeodynamics • Gordon Lithgow and others – Hormesis, endocrine regulation of longevity in flies, worms and mice

Hypothalamopituitaryadrenocortical axis (HPA)

Section of the adrenal illustrating the various zones & hormones

Cortisol: Principal glucocorticoids in humans NE and E: Principal catecholamines in humans

Corticosterone levels in young (3 -5 mo. ) & aged (24 -28 mo. ) rats during one hour of immobilization stress followed by 4 hours of post stress recovery

Generic neuroendocrine axis Hypothalamo-pituitaryadrenal-cortical axis (HPA)

Anterior pituitary & its major hormones; target endocrines & their hormones

Exposure to Stress Generates: • Specific responses: vary with the stimulus and generate different responses with each stimulus. • Nonspecific responses: (also called nonspecialized) are always the same – regardless of the stimulus – mediated through stimulation of neural, endocrine, and immune axis

glucagon secretion

The hypothalamic pituitary connections with major hypophysiotropic hormones

Hypothalamus, limbic nuclei, cerebral connections

Some physiologic and pathologic responses to stress in selected organs

sympathetic activity)

Additional Notes Mutant flies & worms obtained by knocking out the receptor for GH & IGF-1 Prolongation of life span is less efficient in mammals than in worm/flies because greater difficulty in mammals to switch from a preponderant aerobic source of energy to an anaerobic one (Shane & Johnson, 2003, Developmental Cell, 5, 197)