CORNELL BIONB 4930 - Study Notes (19 pages)

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Study Notes



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Study Notes

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Pages:
19
School:
Cornell University
Course:
Bionb 4930 - Developmental Neurobiology

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Neurobiology of Aging 23 2002 921 939 Sex stress and the hippocampus allostasis allostatic load and the aging process Bruce S McEwen Harold and Margaret Milliken Hatch Laboratory of Neuroendocrinology Rockefeller University 1230 York Avenue New York NY 10021 USA Received 20 September 2001 received in revised form 17 December 2001 accepted 10 January 2002 Abstract The adaptive responses of the body that maintain homeostasis in response to stressors can be called allostasis meaning achieving stability through change Mediators produced by the immune system autonomic nervous system ANS and hypothalamo pituitary adrenal HPA axis produce allostasis The brain also shows allostasis involving the activation of nerve cell activity and the release of neurotransmitters When the individual is challenged repeatedly or when the allostatic systems remain turned on when no longer needed the mediators of allostasis can produce a wear and tear on the body and brain that has been termed allostatic load Examples of allostatic load include the accumulation of abdominal fat the loss of bone minerals and the atrophy of nerve cells in the hippocampus Studies of the hippocampus as a target of stress and sex hormones have revealed a considerable degree of structural plasticity and remodeling in the adult brain that differs between the sexes Three forms of hippocampal structural plasticity are affected by circulating hormones 1 repeated stress causes remodeling of dendrites in the CA3 region 2 different modalities of stress suppress neurogenesis of dentate gyrus granule neurons 3 ovarian steroids regulate synapse formation during the estrous cycle of female rats All three forms of structural remodeling of the hippocampus are mediated by hormones working in concert with excitatory amino acids EAA and NMDA receptors EAA and NMDA receptors are also involved in neuronal death that is caused in pyramidal neurons by seizures by ischemia and by severe and prolonged psychosocial stress The aging brain



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