QUOTE(DWB04 @ Mar 1 2005, 12:52 PM)
I should mention Dopamine.......it converts to noradrenaline
Noradrenaline converts to norepinephrine.....
ah I see the confusion.....
noradrenalinecture is the process explaining the rise in serotonin and the endorphin release in accupuncture......
Ok here's some information related to the adrenal glands part of the endocrine system we talked about....and related to the mastergland... the pituitary
The two adrenal glands are located immediately anterior to the kidneys, encased in a connective tissue capsule and usually partially buried in an island of fat. Like the kidneys, the adrenal glands lie beneath the peritoneum (i.e. they are retroperitoneal). The exact location relative to the kidney and the shape of the adrenal gland vary among species.
Inspection of a mammalian adrenal gland that has been sectioned reveals two distinct regions, as demonstrated to the right with a sheep adrenal (click the image to flip between surface and cut views):
An inner medulla,
which is a source of the catecholamines epinephrine and norepinephrine. The chromaffin cell is the principle cell type. The medulla is richly innervated by preganglionic sympathetic fibers and is, in essence, an extension of the sympathetic nervous system.
An outer cortex, which secretes several classes of steroid hormones (glucocorticoids and mineralocorticoids, plus a few others). Histologic examination of the cortex reveals three concentric zones of cells that differ in the major steroid hormones they secrete.
Despite their organization into a single gland, the medulla and cortex are functionally different endocrine organs, and have different embryological origins. The medulla derives from ectoderm (neural crest), while the cortex develops from mesoderm. The utility, if any, of having them together in one discrete organ is not obvious. In some species, amphibians and certain fish, for example, two separate organs are found.
Adrenal Medullary Hormones
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Cells in the adrenal medulla synthesize and secrete norepinephrine and epinephrine. The ratio of these two catecholamines differs considerably among species: in humans, cats and chickens, roughly 80, 60 and 30% of the catecholamine output is epinephrine. Following release into blood, these hormones bind adrenergic receptors on target cells, where they induce essentially the same effects as direct sympathetic nervous stimulation.
Synthesis and Secretion of Catecholamines
Synthesis of catecholamines begins with the amino acid tyrosine, which is taken up by chromaffin cells in the medulla and converted to norepinephrine and epinephrine through the following steps:
Norepinephine and epinephrine are stored in electron-dense granules which also contain ATP and several neuropeptides. Secretion of these hormones is stimulated by acetylcholine release from preganglionic sympathetic fibers innervating the medulla. Many types of "stresses" stimulate such secretion, including exercise, hypoglycemia and trauma. Following secretion into blood, the catecholamines bind loosely to and are carried in the circulation by albumin and perhaps other serum proteins.
Adrenergic Receptors and Mechanism of Action
The physiologic effects of epinephrine and norepinephrine are initiated by their binding to adrenergic receptors on the surface of target cells. These receptors are prototypical examples of seven-pass transmembrane proteins that are coupled to G proteins which stimulate or inhibit intracellular signalling pathways.
Complex physiologic responses result from adrenal medullary stimulation because there are multiple receptor types which are differentially expressed in different tissues and cells. The alpha and beta adrenergic receptors and their subtypes were originally defined by differential binding of various agonists and antagnonists and, more recently, by analysis of molecular clones.
Receptor Effectively Binds Effect of Ligand Binding
Alpha1 Epinephrine, Norepinphrine Increased free calcium
Alpha2 Epinephrine, Norepinphrine Decreased cyclic AMP
Beta1 Epinephrine, Norepinphrine Increased cyclic AMP
Beta2 Epinephrine Increased cyclic AMP
Physiologic Effects of Medullary Hormones
In general, circulating epinephrine and norepinephrine released from the adrenal medulla have the same effects on target organs as direct stimulation by sympathetic nerves, although their effect is longer lasting. Additionally, of course, circulating hormones can cause effects in cells and tissues that are not directly innervated. The physiologic consequences of medullary catecholamine release are justifiably framed as responses which aid in
dealing with stress. These effects can be predicted to some degree by imagining what would be needed if, for example, you were trapped in Jurassic Park when the power went off. A listing of some major effects mediated by epinephrine and norepinephrine are:
Increased rate and force of contraction of the heart muscle: this is predominantly an effect of epinephrine acting through beta receptors.
Constriction of blood vessels: norepinephrine, in particular, causes widespread vasoconstriction, resulting in increased resistance and hence arterial blood pressure.Dilation of bronchioles: assists in pulmonary ventilation.
Stimulation of lipolysis in fat cells: this provides fatty acids for energy production in many tissues and aids in conservation of dwindling reserves of blood glucose.
Increased metabolic rate: oxygen consumption and heat production increase throughout the body in response to epinephrine. Medullary hormones also promote breakdown of glycogen in skeletal muscle to provide glucose for energy production.
Dilation of the pupils: particularly important in situations where you are surrounded by velociraptors under conditions of low ambient light.
Inhibition of certain "non-essential" processes: an example is inhibition of gastrointestinal secretion and motor activity.
Common stimuli for secretion of adrenomedullary hormones include exercise, hypoglycemia, hemorrhage and
emotional distress. http://arbl.cvmbs.colostate.edu/hbooks/pat...al/anatomy.htmlhttp://arbl.cvmbs.colostate.edu/hbooks/pat...edhormones.html