7adrenal medulla

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Adrenal medulla

Medullary part of the adrenal gland (on the pointer).

Theadrenal medulla(Latin: medulla glandulae supra-

renalis) is part of the adrenal gland. It is located at

the center of the gland, being surrounded by theadrenal

cortex. It is the innermost part of the adrenal gland,

consisting of cells that secreteepinephrine(adrenaline),

norepinephrine (noradrenaline), and a small amount of

dopamine in response to stimulation by sympatheticpreganglionic neurons.

1 Basic

The adrenal medulla consists of irregularly shaped cells

grouped around blood vessels. These cells are intimately

connected with the sympathetic division of the autonomic

nervous system (ANS). In fact, these adrenal medullary

cells are modified postganglionic neurons, and pregan-

glionic autonomic nerve fibers lead to them directly from

the central nervous system. The adrenal medulla there-fore affects available energy; heart rate; and metabolism.

2 Function

Rather than releasing a neurotransmitter, the cells of the

adrenal medulla secretehormones.

Composed mainly of hormone-producing chromaffin

cells, the adrenal medulla is the principal site of the con-

version of theamino acid tyrosine into thecatecholamines

epinephrine, norepinephrine, and dopamine.Because the ANS, specifically the sympathetic division,

exerts direct control over the chromaffin cells the hor-

mone release can occur rather quickly. In response to

stressorssuch asexerciseor imminent danger, medullary

cells release catecholamines into the blood in a 17:3 ratio

of adrenaline to noradrenaline.[1]

Notable effects of adrenaline and noradrenaline include

increased heart rate and blood pressure,blood vessel con-

striction in the skin and gastrointestinal tract, smooth

muscle (bronchioleand capillary) dilation, and increased

metabolism, all of which are characteristic of thefight-or-

flight response. Release of catecholamines is stimulated

by nerve impulses, and receptors for catecholamines arewidely distributed throughout the body.

3 Origin

Medullary cells are derived from the embryonic neural

crestand, as such, are simply modifiedneurons.

In particular, they are modified postganglionic cells of

theautonomic nervous systemthat have lost theiraxons

anddendrites, receiving innervation from corresponding

preganglionic fibers. The cells form clusters around largeblood vessels.

Moreover, as the synapses between pre- and postgan-

glionic fibers are called ganglia, the adrenal medulla is

actually a ganglion of the sympathetic nervous system.

4 Pathology

Neoplasms include:[2]

Pheochromocytoma (most common), acatecholamine-secreting tumor of the adrenal

medulla

Neuroblastoma, a neuroendocrine tumor of any neu-

ral crest tissue of the sympathetic nervous system

Ganglioneuroma, a tumor in the nerve cells of the

peripheral nervous system

The adrenal medulla may be poorly formed or absent in

cases of absent adrenal gland. The deficiency in circu-

lating catecholamines is mildly symptomatic due to com-

pensation by theautonomous nervous system, except inepisodes of hypoglycemia where glycogenolysis cannot be

stimulated by circulating epinephrine .[2]

1
https://en.wikipedia.org/wiki/Glycogenolysishttps://en.wikipedia.org/wiki/Hypoglycemiahttps://en.wikipedia.org/wiki/Autonomous_nervous_systemhttps://en.wikipedia.org/wiki/Absent_adrenal_glandhttps://en.wikipedia.org/wiki/Ganglioneuromahttps://en.wikipedia.org/wiki/Neuroblastomahttps://en.wikipedia.org/wiki/Catecholaminehttps://en.wikipedia.org/wiki/Pheochromocytomahttps://en.wikipedia.org/wiki/Autonomic_ganglionhttps://en.wikipedia.org/wiki/Preganglionic_fiberhttps://en.wikipedia.org/wiki/Dendritehttps://en.wikipedia.org/wiki/Axonhttps://en.wikipedia.org/wiki/Autonomic_nervous_systemhttps://en.wikipedia.org/wiki/Postganglionic_cellhttps://en.wikipedia.org/wiki/Neuronhttps://en.wikipedia.org/wiki/Neural_cresthttps://en.wikipedia.org/wiki/Neural_cresthttps://en.wikipedia.org/wiki/Embryohttps://en.wikipedia.org/wiki/Fight-or-flight_responsehttps://en.wikipedia.org/wiki/Fight-or-flight_responsehttps://en.wikipedia.org/wiki/Metabolismhttps://en.wikipedia.org/wiki/Bronchiolehttps://en.wikipedia.org/wiki/Vasoconstrictionhttps://en.wikipedia.org/wiki/Vasoconstrictionhttps://en.wikipedia.org/wiki/Blood_pressurehttps://en.wikipedia.org/wiki/Heart_ratehttps://en.wikipedia.org/wiki/Exercisehttps://en.wikipedia.org/wiki/Stressorhttps://en.wikipedia.org/wiki/Catecholaminehttps://en.wikipedia.org/wiki/Tyrosinehttps://en.wikipedia.org/wiki/Amino_acidhttps://en.wikipedia.org/wiki/Chromaffin_cellhttps://en.wikipedia.org/wiki/Chromaffin_cellhttps://en.wikipedia.org/wiki/Hormonehttps://en.wikipedia.org/wiki/Preganglionic_neuronshttps://en.wikipedia.org/wiki/Sympathetic_nervous_systemhttps://en.wikipedia.org/wiki/Dopaminehttps://en.wikipedia.org/wiki/Norepinephrinehttps://en.wikipedia.org/wiki/Epinephrinehttps://en.wikipedia.org/wiki/Adrenal_cortexhttps://en.wikipedia.org/wiki/Adrenal_cortexhttps://en.wikipedia.org/wiki/Adrenal_glandhttps://en.wikipedia.org/wiki/Latin_language


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2 7 EXTERNAL LINKS

In dopamine beta hydroxylase deficiency, the en-

tire body cannot efficiently produce epinephrine and

norepinephrine from dopamine, this results in severe

dysautonomiabut most crucially due to autonomous ner-

vous system failure which requires epinephrine and nore-

pinephrine asneurotransmitters, dopamine being used in

this pathology as an inadequate substitute.[2][3]

5 See also

Adrenal gland

History of catecholamine research

6 References

[1] Introduction to Autonomics, Part 2 - Page 5 of 12 anatomymodule atmed.umich.edu

[2] Fung, M. M.; Viveros, O. H.; OConnor, D. T. (16

November 2007). Diseases of the adrenal medulla.

Acta Physiologica 192 (2): 325335.doi:10.1111/j.1748-

1716.2007.01809.x.PMC 2576282.PMID 18021328.

[3] Robertson, D; Haile, V; Perry, SE; Robertson, RM;

Phillips JA, 3rd; Biaggioni, I (July 1991). Dopamine

beta-hydroxylase deficiency. A genetic disorder of car-

diovascular regulation.. Hypertension 18 (1): 18.

doi:10.1161/01.hyp.18.1.1. PMID 1677640.

7 External links

Anatomy photo:40:04-0202 at the SUNY Down-

state Medical Center - Posterior Abdominal Wall:

Blood Supply to the Suprarenal Glands

Anatomy Atlases - Microscopic Anatomy, plate

15.292- Adrenal Gland
http://www.anatomyatlases.org/MicroscopicAnatomy/Section15/Plate15292.shtmlhttp://www.anatomyatlases.org/MicroscopicAnatomy/Section15/Plate15292.shtmlhttp://ect.downstate.edu/courseware/haonline/labs/l40/040202.htmhttps://www.ncbi.nlm.nih.gov/pubmed/1677640https://en.wikipedia.org/wiki/PubMed_Identifierhttps://dx.doi.org/10.1161%252F01.hyp.18.1.1https://en.wikipedia.org/wiki/Digital_object_identifierhttps://www.ncbi.nlm.nih.gov/pubmed/18021328https://en.wikipedia.org/wiki/PubMed_Identifierhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC2576282https://en.wikipedia.org/wiki/PubMed_Centralhttps://dx.doi.org/10.1111%252Fj.1748-1716.2007.01809.xhttps://dx.doi.org/10.1111%252Fj.1748-1716.2007.01809.xhttps://en.wikipedia.org/wiki/Digital_object_identifierhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC2576282https://en.wikipedia.org/wiki/University_of_Michiganhttp://www.med.umich.edu/lrc/coursepages/m1/anatomy2010/html/modules/intro_autonomics_2_module/autonomics_05.htmlhttps://en.wikipedia.org/wiki/History_of_catecholamine_researchhttps://en.wikipedia.org/wiki/Adrenal_glandhttps://en.wikipedia.org/wiki/Neurotransmitterhttps://en.wikipedia.org/wiki/Dysautonomiahttps://en.wikipedia.org/wiki/Dopamine_beta_hydroxylase_deficiency


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