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Pituicytes are located in the pars nervosa of the posterior pituitary and interspersed with unmyelinated axons and Herring bodies.They generally stain dark purple with an H&E stain and are among the easiest structures to identify in the region.
Herring bodies or neurosecretory bodies are structures found in the posterior pituitary. They represent the terminal end of the axons from the hypothalamus, and hormones are temporarily stored in these locations. They are neurosecretory terminals. [1]
The posterior pituitary is not glandular as is the anterior pituitary. Instead, it is largely a collection of axonal projections from the hypothalamus that terminate behind the anterior pituitary, and serve as a site for the secretion of neurohypophysial hormones ( oxytocin and vasopressin ) directly into the blood. [ 2 ]
Neuropil has been found in the following regions: outer neocortex layer, barrel cortex, inner plexiform layer and outer plexiform layer, posterior pituitary, and glomeruli of the cerebellum. These are all found in humans, with the exception of the barrel cortex, but many species have counterparts similar to our own regions of neuropil.
The PVN contains magnocellular neurosecretory cells whose axons extend into the posterior pituitary, parvocellular neurosecretory cells that project to the median eminence, ultimately signalling to the anterior pituitary, and several populations of other cells that project to many different brain regions including parvocellular preautonomic cells that project to the brainstem and spinal cord.
The process occurs as follows: in some hypothalamic cells there are osmoreceptors which respond to hyperosmolality in body fluids by signalling the posterior pituitary gland to secrete ADH. [6] This keeps serum sodium concentration – a proxy for solute concentration – at normal levels, prevents hypernatremia and turns off the osmoreceptors. [7]
It is also known as neurohypophyseal diabetes insipidus, [2] [3] referring to the posterior pituitary (neurohypophysis), which receives vasopressin from the hypothalamus in the brain, via the hypothalamo-hypophyseal tract in the pituitary stalk. This condition has only polyuria in common with diabetes. Although not mutually exclusive, with most ...
The oxytocin and vasopressin that is released at the posterior pituitary gland enters the blood, and cannot re-enter the brain because the blood–brain barrier does not allow oxytocin and vasopressin through, but the oxytocin and vasopressin that is released from dendrites acts within the brain. Oxytocin neurons themselves express oxytocin ...