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Adrenal Glands - Anatomy & Physiology (view source)
Revision as of 15:43, 11 September 2008
, 15:43, 11 September 2008→'''Glucocorticoids'''
===='''Glucocorticoids'''====
===='''Glucocorticoids'''====
These hormones are important in regulating glucose metabolism; the most important of them is '''cotisol'''. This is formed within the zona fasiculata by the conversion of pregnenolone directly to cortisol. It is transported by cortisol-binding globulin and has a half-life of 90 minutes.
'''Regulation of Synthesis and Secretion'''
This is regulated by the hypothalamus-pituitary adrenal axis as follows:
* An environmental or internal stimuli (such as stress or light regulating the circadian rhythm) causes the hypothalamus to release ACTH-releasing hormone ('''ACTH-RH''').
* ACTH-RH flows to the pituitary gland stimulating the production of adrenocorticotrophic hormone ('''ACTH''').
* ACTH binds to receptors on cells of the adrenal cortex. Thus activating adenyl cyclase.
* This leads to increased cAMP levels and the mobilization of more cholesterol and so the production of more cortisol. This is the rate limiting step and is determined by the P-450-enzyme.
* Cortisol then has a negative feedback effect on ACTH-RH and ACTH secretion.
'''Action'''
These are essential hormones and have multiple effects around the body.
* Cortisol has a '''permissive action'''. I.e. without cortisol certain chemical reactions within cells are unable to occur, for example the production of epinephrine and glucagon.
* Cortisol is a '''stress hormone'''. In times of stress it is released and enhances the effect of norepinephrine on blood pressure. It is also essential for the day to day maintenance of normal blood pressure. It will also stimulate gluconeogenesis and inhibit certain tissues utilization of glucose.
* It stimulates degradation of fats and proteins.
* It inhibits DNA synthesis in some tissues. This along with degradation of protein results in a '''growth-inhibiting effect''' in times of stress.
* It can have '''anti-inflammatory''' effects. It inhibits the formation of prostaglandins and cytokines and reduces the ability of white blood cells being transported to an injured area. It helps keep in check inflammatory processes that could potentially cause tissue damage.
* It is also '''immunosuppressive''' by reducing the lymphocyte numbers in circulation and reducing antibody production.
===='''Androgens'''====
==Histology of the Adrenal Glands==
==Histology of the Adrenal Glands==