[lou_lou]

http://www.answers.com/adrenal+medul...ookup&nafid=27

ADRENAL MEDULLA

The adrenal medulla is part of the adrenal gland. It is located at the center of the gland, being surrounded by the adrenal cortex.


Function
Composed mainly of hormone-producing chromaffin cells, the adrenal medulla is the principal site of the conversion of the amino acid tyrosine into the catecholamines adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine.

In response to stressors such as exercise or imminent danger, medullary cells release catecholamines into the blood in a 85:15 ratio of adrenaline to noradrenaline. [1]

Notable effects of adrenaline and noradrenaline include increased heart rate and blood pressure, blood vessel constriction, bronchiole dilation, and increased metabolism, all of which are characteristic of the fight-or-flight response. Release of catecholamines is stimualted by nerve impulses, and receptors for catecholamines are widely distributed throughout the body.


Origin
Medullary cells are derived from the embryonic neural crest and, as such, are simply modified neurons.

In particular, they are modified postganglionic cells of the sympathetic nervous system that have lost their axons and dendrites, receiving innervation from corresponding preganglionic fibers.

Moreover, as the synapses between pre- and postganglionic fibers are called ganglia, the adrenal medulla is actually a ganglion of the sympathetic nervous system.


~~~~~~

substantia ni·gra
(nī'grə, nĭg'rə)
n.
A layer of large pigmented nerve cells in the mesencephalon that produce dopamine and whose destruction is associated with Parkinson's disease. Also called nigra.

http://www.answers.com/substantia%20nigra

MESENCEPHALON /
In biological anatomy, the mesencephalon (or midbrain) is the middle of three vesicles that arise from the neural tube that forms the brain of developing animals. Caudally the mesencephalon adjoins the pons (metencephalon) and rostrally it adjoins the diencephalon (Thalamus, hypothalamus, et al).

http://www.answers.com/topic/mesencephalon

[lou_lou]

The Adrenal glands
http://www.becomehealthynow.com/ebookprint.php?id=679

Learn about the adrenal glands...

[lou_lou]

Neurosecretion
The synthesis and release of hormones by neurons.

Such neurons are called neurosecretory cells, and their products are often called neurohormones. Like conventional (that is, nonglandular or ordinary) neurons, neurosecretory cells are able to receive signals from other neurons. But unlike ordinary neurons that have cell-to-cell communication over short distances at synapses, neurosecretory cells release their product into an extracellular space that may be at some distance from the target cells.

In an organism with a circulatory system, the neurohormones are typically sent by the vascular route to their target, whereas in lower invertebrates that lack an organized circulatory system the neurohormones apparently simply diffuse from the release site to the target.

It is now clear that the nervous and endocrine systems interact in many ways, as in the suckling reflex of mammals (where the hormone oxytocin, a neurohormone, elicits milk ejection and is reflexly released in response to nerve impulses generated by stimulation of the nipples), and neurosecretory cells form a major link between them. See also Endocrine system (invertebrate); Endocrine system (vertebrate).

http://www.answers.com/topic/neurosecretion

[lou_lou]

Beta - Endorphins
~~~
Endorphins are endogenous opioid biochemical compounds. They are polypeptides produced by the pituitary gland and the hypothalamus in vertebrates, and they resemble the opiates in their abilities to produce analgesia and a sense of well-being. In other words, they might work as "natural pain killers." Using drugs may increase the effects of the endorphins.

The term "endorphin" implies a pharmacological activity (analogous to the activity of the corticosteroid category of biochemicals) as opposed to a specific chemical formulation. It consists of two parts: endo- and -orphin; these are short forms of the words endogenous and morphine, intended to mean "a morphine-like substance originating from within the body." [1]

The term endorphin rush has been adopted in popular speech to refer to feelings of exhilaration brought on by pain, danger, or other forms of stress,[2] supposedly due to the influence of endorphins. However, this term does not occur in the medical literature.
my imput / We call "Runners high"

http://www.answers.com/beta-endorphi...ookup&nafid=27