Term
| Describe the mechanism by which the HPA axis has an impact on stress. |
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Definition
| CRH produced by cells in the paraventricular nucleus- ACTH released by corticotroph cells in the anterior pituitary- ACTH increases synthesis of corticosteroid hormones in the adrenal cortex (cortisol most important). |
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Term
| What are corticosteroids important signalling hormones for? |
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Definition
1) Diurnal rhythms of activity
2) Homeostatic responses to stress
3) Potential damaging effects when persistently elevated by chronic stress. |
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Term
| What is the relevance of the lipophyllic properties of corticosteroids? |
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Definition
| They can cross the blood brain barrier. |
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Term
| What are the 2 corticosteroid receptors? |
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Definition
1) Mineralocorticoid receptors: high affinity so occupied most of the time
2) Glucocorticoid receptors: low affinity so only activated by high levels during stress. |
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Term
| What are some of the acute actions of corticosteroids? |
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Definition
1) Increased glucose availability
2) Reduction in some vegetative functions
3) Maintenance of vascular tone |
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Term
| What impact can stress have on the latent herpes simplex virus? |
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Definition
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Term
| What is the relationship between stress and wound healing? |
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Definition
| Stress disrupts the production of some proinflammatory cytokines which causes a delayin wound repair. |
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Term
| Explain steroid negative feedback on the HPA axis. |
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Definition
1) In the hippocamput it increases inhibitory input to the PVN
2) In the PVN it switches off activity (immediate response) and reduces the synthesis of CRH (delayed response)
3) In the pituitary it reduces the synthesis of ACTH. |
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Term
| What is the relationship between depressed patients and corticosteroids? |
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Definition
| Depressed patients have impaired negative feedback of corticosteroids and lower glucocorticoid receptor levels. Corticosteroids have major effects on the expression and function of serotonin receptors and can modulate serotonergic neurotransmission. |
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Term
| How does the dexamethasone suppression test work? |
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Definition
| Desamethasone is a synthetic corticosteroid which normally suppresses HPA activity but does not in depressed patients. |
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Term
| How can stress ipact on cognition? |
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Definition
| Corticosteoids cause metabolic compromise to neurones and exacerbate neurotoxic effects of insults. This causes hippocampal damage can be measured as atrophy and leads to effects on cognition and negative feedback on the HPA. |
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