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Schematic of the HPA axis (CRH, corticotropin-releasing hormone; ACTH, adrenocorticotropic hormone) Hypothalamus, pituitary gland, and adrenal cortex The hypothalamic–pituitary–adrenal axis (HPA axis or HTPA axis) is a complex set of direct influences and feedback interactions among three components: the hypothalamus (a part of the brain located below the thalamus), the pituitary gland (a ...
Neural progenitors that become hippocampal principal neurons (pyramidal and granular cells) arise from the ventricular zone of the lateral ventricle.In contrast to neural proliferation that leads to cortical formation, hippocampal precursors are produced directly in the ventricular zone because there is no subventricular zone or outer subventricular zone adjacent to the hippocampus.
This process is repressed by glucocorticoids; this inhibitory feedback helps maintain homeostasis of the stress response. [ 10 ] Once released by the hypothalamus, CRH travels through the hypophyseal portal system to the anterior pituitary, where it binds to G protein-coupled receptors on the corticotropic cell membrane and stimulates cAMP ...
CRH is secreted by the paraventricular nucleus (PVN) of the hypothalamus in response to stress. Increased CRH production has been observed to be associated with Alzheimer's disease and major depression, [6] and autosomal recessive hypothalamic corticotropin deficiency has multiple and potentially fatal metabolic consequences including ...
In addition to the effects listed above, use of high-dose glucocorticoids for only a few days begins to produce suppression of the patient's adrenal glands suppressing hypothalamic corticotropin-releasing hormone (CRH) leading to suppressed production of adrenocorticotropic hormone (ACTH) by the anterior pituitary. [21]
The hypothalamus contains neurons that react strongly to steroids and glucocorticoids (the steroid hormones of the adrenal gland, released in response to ACTH). It also contains specialized glucose-sensitive neurons (in the arcuate nucleus and ventromedial hypothalamus ), which are important for appetite .
Glucocorticoids secreted from the adrenal cortex work to inhibit CRH secretion by the hypothalamus, which in turn decreases anterior pituitary secretion of ACTH. Glucocorticoids may also inhibit the rates of POMC gene transcription and peptide synthesis. The latter is an example of a slow feedback loop, which works on the order of hours to days ...
Situated between the glomerulosa and reticularis, the cells of the zona fasciculata synthesize and secrete glucocorticoids (such as 11-deoxycorticosterone, corticosterone, and cortisol), as well as small amounts of adrenal androgens and estrogens. [14] The zona fasciculata has more 3β-hydroxysteroid dehydrogenase activity than the zona ...