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Adrenal medulla
 
 
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The adrenal medulla is part of the adrenal gland
Adrenal gland

In mammals, the adrenal glands are the star-shaped endocrine glands that sit on top of the kidneys; their name indicates that position . They are chiefly responsible for regulating the stress response through the biosynthesis of corticosteroids and catecholamines, including cortisol and adrenaline, respectively....
. It is located at the center of the gland, being surrounded by the adrenal cortex
Adrenal cortex

Situated along the perimeter of the adrenal gland, the adrenal cortex mediates the stress response through the production of mineralocorticoids and glucocorticoids, including aldosterone and cortisol respectively....
.

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. In fact, these adrenal medullary cells are modified postganglionic neurons, and preganglionic autonomic nerve fibers lead to them directly from the central nervous system.

osed mainly of hormone-producing chromaffin cell
Chromaffin cell

Chromaffin cells are neuroendocrine cells found in the adrenal medulla of the adrenal gland and in other autonomic ganglion of the sympathetic nervous system....
s, the adrenal medulla is the principal site of the conversion of the amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
 tyrosine
Tyrosine

Tyrosine or 4-hydroxyphenylalanine, is one of the 20 amino acids that are used by cell to protein biosynthesis proteins. This is a non-essential amino acid and it is found in casein....
 into the catecholamine
Catecholamine

Catecholamines are chemical compounds derived from the amino acid tyrosine. Their name is derived from the fact that they contain catechol and amine moieties....
s adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine
Dopamine

Dopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the human brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors ? D1, D2, D3, D4 and D5, and their variants....
.

In response to stressor
Stressor

In chemistry, a stressor is something that either speeds up a reaction rate or keeps the reaction rate the same. Stressors include light, temperature and noise health effects....
s such as exercise or imminent danger, medullary cells release catecholamine
Catecholamine

Catecholamines are chemical compounds derived from the amino acid tyrosine. Their name is derived from the fact that they contain catechol and amine moieties....
s into the blood in an 17:3 ratio of adrenaline to noradrenaline.

Notable effects of adrenaline and noradrenaline include increased heart rate
Heart rate

Heart rate is a measure of the number of heart beats per minute . The average resting human heart rate is about 70 bpm for adult males and 75 bpm for adult females....
 and blood pressure
Blood pressure

Blood pressure is the pressure exerted by circulating blood on the walls of blood vessels, and constitutes one of the principal vital signs. The pressure of the circulating blood decreases as it moves away from the heart through artery and capillary, and toward the heart through veins....
, blood vessel constriction
Vasoconstriction

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, arterioles and veins....
 in the skin and gastrointestinal tract, blood vessel dialation in skeletal muscles, bronchiole
Bronchiole

The bronchioles or bronchioli are the first airway branches that no longer contain cartilage. They are branches of the bronchi, and are smaller than one millimeter in diameter....
 dilation, and decreased metabolism
Metabolism

Metabolism is the set of chemical reactions that occur in living organisms in order to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments....
, all of which are characteristic of the fight-or-flight response
Fight-or-flight response

'The 'fight-or-flight response', also called the fright, fight or flight response', 'hyperarousal' or the 'acute stress response', was first described by Walter Cannon in 1915....
.






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Encyclopedia


The adrenal medulla is part of the adrenal gland
Adrenal gland

In mammals, the adrenal glands are the star-shaped endocrine glands that sit on top of the kidneys; their name indicates that position . They are chiefly responsible for regulating the stress response through the biosynthesis of corticosteroids and catecholamines, including cortisol and adrenaline, respectively....
. It is located at the center of the gland, being surrounded by the adrenal cortex
Adrenal cortex

Situated along the perimeter of the adrenal gland, the adrenal cortex mediates the stress response through the production of mineralocorticoids and glucocorticoids, including aldosterone and cortisol respectively....
.

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. In fact, these adrenal medullary cells are modified postganglionic neurons, and preganglionic autonomic nerve fibers lead to them directly from the central nervous system.

Function

Composed mainly of hormone-producing chromaffin cell
Chromaffin cell

Chromaffin cells are neuroendocrine cells found in the adrenal medulla of the adrenal gland and in other autonomic ganglion of the sympathetic nervous system....
s, the adrenal medulla is the principal site of the conversion of the amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
 tyrosine
Tyrosine

Tyrosine or 4-hydroxyphenylalanine, is one of the 20 amino acids that are used by cell to protein biosynthesis proteins. This is a non-essential amino acid and it is found in casein....
 into the catecholamine
Catecholamine

Catecholamines are chemical compounds derived from the amino acid tyrosine. Their name is derived from the fact that they contain catechol and amine moieties....
s adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine
Dopamine

Dopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the human brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors ? D1, D2, D3, D4 and D5, and their variants....
.

In response to stressor
Stressor

In chemistry, a stressor is something that either speeds up a reaction rate or keeps the reaction rate the same. Stressors include light, temperature and noise health effects....
s such as exercise or imminent danger, medullary cells release catecholamine
Catecholamine

Catecholamines are chemical compounds derived from the amino acid tyrosine. Their name is derived from the fact that they contain catechol and amine moieties....
s into the blood in an 17:3 ratio of adrenaline to noradrenaline.

Notable effects of adrenaline and noradrenaline include increased heart rate
Heart rate

Heart rate is a measure of the number of heart beats per minute . The average resting human heart rate is about 70 bpm for adult males and 75 bpm for adult females....
 and blood pressure
Blood pressure

Blood pressure is the pressure exerted by circulating blood on the walls of blood vessels, and constitutes one of the principal vital signs. The pressure of the circulating blood decreases as it moves away from the heart through artery and capillary, and toward the heart through veins....
, blood vessel constriction
Vasoconstriction

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, particularly the large arteries, arterioles and veins....
 in the skin and gastrointestinal tract, blood vessel dialation in skeletal muscles, bronchiole
Bronchiole

The bronchioles or bronchioli are the first airway branches that no longer contain cartilage. They are branches of the bronchi, and are smaller than one millimeter in diameter....
 dilation, and decreased metabolism
Metabolism

Metabolism is the set of chemical reactions that occur in living organisms in order to maintain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments....
, all of which are characteristic of the fight-or-flight response
Fight-or-flight response

'The 'fight-or-flight response', also called the fright, fight or flight response', 'hyperarousal' or the 'acute stress response', was first described by Walter Cannon in 1915....
. Release of catecholamine
Catecholamine

Catecholamines are chemical compounds derived from the amino acid tyrosine. Their name is derived from the fact that they contain catechol and amine moieties....
s is stimulated by nerve impulses, and receptors for catecholamine
Catecholamine

Catecholamines are chemical compounds derived from the amino acid tyrosine. Their name is derived from the fact that they contain catechol and amine moieties....
s are widely distributed throughout the body.

Origin

Medullary cells are derived from the embryo
Embryo

An embryo is a multicellular organism ploidy eukaryote in its earliest stage of development, from the time of first cell division until birth, Egg , or germination....
nic neural crest
Neural crest

The neural crest, a transient component of the ectoderm, is located in between the neural tube and the epidermis of an embryo during neural tube formation....
 and, as such, are simply modified neuron
Neuron

Neurons are responsive cell in the nervous system that process and transmit information by electrochemical Signal . They are the core components of the brain, the vertebrate spinal cord, the invertebrate ventral nerve cord, and the peripheral nerves....
s.

In particular, they are modified postganglionic cells of the sympathetic nervous system
Sympathetic nervous system

The Sympathetic Nervous System is a branch of the autonomic nervous system along with the enteric nervous system and parasympathetic nervous system....
 that have lost their axon
Axon

An axon or nerve fiber is a long, slender projectionof a nerve cell, or neuron, that conducts action potentialaway from the neuron's cell body or soma....
s and dendrite
Dendrite

Dendrites are the branched projections of a neuron that act to conduct the electrochemical stimulation received from other neural cells to the cell body, or Soma , of the neuron from which the dendrites project....
s, receiving innervation from corresponding preganglionic fibers.

Moreover, as the synapses between pre- and postganglionic fibers are called ganglia
Autonomic ganglion

Autonomic ganglia are clusters of neuronal cell bodies and their dendrites and are essentially a junction between autonomic nerves originating from the central nervous system and autonomic nerves innervating their target organs in the periphery....
, the adrenal medulla is actually a ganglion of the sympathetic nervous system.

Pathology

Neoplasms including:
  • Pheochromocytoma
    Pheochromocytoma

    A phaeochromocytoma is a neuroendocrine tumor of the Adrenal medulla of the adrenal glands , or extra-adrenal chromaffin tissue that failed to involute after birth and secretes excessive amounts of catecholamines, usually epinephrine and norepinephrine....
     (most common) a catecholamine
    Catecholamine

    Catecholamines are chemical compounds derived from the amino acid tyrosine. Their name is derived from the fact that they contain catechol and amine moieties....
    -secreting tumor of the adrenal medulla
  • Neuroblastoma
    Neuroblastoma

    Neuroblastoma is the most common extracranial solid cancer in childhood and the most common cancer in infancy, with an annual incidence of about 650 new cases per year in the US....
     a neuroendocrine tumor of any neural crest tissue of the sympathetic nervous system
  • Ganglioneuroma
    Ganglioneuroma

    Ganglioneuroma is a tumor of the sympathetic nerve fibers arising from neural crest cells.For example, it can be found also in the eye , or in the medulla of adrenal glands....
     a tumor in the nerve cells of the peripheral nervous system


See also

  • Adrenal gland
    Adrenal gland

    In mammals, the adrenal glands are the star-shaped endocrine glands that sit on top of the kidneys; their name indicates that position . They are chiefly responsible for regulating the stress response through the biosynthesis of corticosteroids and catecholamines, including cortisol and adrenaline, respectively....


External links

- "Adrenal Gland"