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Within the thalamus the internal medullary lamina divides the nuclei into anterior, medial, and lateral groups. [13] [14] Derivatives of the diencephalon include the dorsally-located epithalamus (essentially the habenula and annexes) and the perithalamus (prethalamus) containing the zona incerta and the thalamic reticular
These two circumventricular organs are located along the anteroventral region of the third ventricle, called the AV3V region. [2] Between these two organs is the median preoptic nucleus , which has multiple nerve connections with the two organs, as well as with the supraoptic nuclei and blood pressure control centers in the medulla oblongata .
The magnocellular cells in the PVN elaborate and secrete two peptide hormones: oxytocin and vasopressin. These hormones are packaged into large vesicles, which are then transported down the unmyelinated axons of the cells and released from neurosecretory nerve terminals residing in the posterior pituitary gland. [citation needed]
The thyroid secretes thyroxine, the pituitary secretes growth hormone, the pineal secretes melatonin, the testis secretes testosterone, and the ovaries secrete estrogen and progesterone. [2] Glands that signal each other in sequence are often referred to as an axis, such as the hypothalamic–pituitary–adrenal axis.
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 ...
In the cell bodies, the hormones are packaged in large, membrane-bound vesicles that are transported down the axons to the nerve endings. The secretory granules are also stored in packets along the axon called Herring bodies. [citation needed] Similar magnocellular neurons are also found in the paraventricular nucleus. [citation needed]
The anterior pituitary contains several different types of cells [9] that synthesize and secrete hormones. Usually there is one type of cell for each major hormone formed in anterior pituitary. With special stains attached to high-affinity antibodies that bind with distinctive hormone, at least 5 types of cells can be differentiated.
These hypophysiotropic hormones are stimulated by parvocellular neurosecretory cells located in the periventricular area of the hypothalamus. After their release into the capillaries of the third ventricle, the hypophysiotropic hormones travel through what is known as the hypothalamo-pituitary portal circulation.