2. INTRODUCTION
Adrenal glands are triangle shaped glands located
on the top of the kidney.
Each gland consists of a medulla surrounded by
the cortex.
3. ADRENAL MEDULLA
The inner region of adrenal gland.
Is a modified sympathetic ganglion of Autonomic
nervous system.
Occupies central 20% of adrenal gland.
Consists of rounded groups of relatively large &
granular cells called chromaffin cells/
pheochromocytes.
Chromaffin cells contain granules composed of
catecholamines, adenine nucleotides, proteins &
lipids
4. Proteins of these granules is referred to as
chromogranin.
The human adrenal medulla consists of 2 types of
cells
1. Adrenalin (A) storing cells
2. Nor adrenalin (N) storing cells
One type of cells secrete adrenaline & the other type
secrete nor epinephrine.
These hormones are stored in the form of chromaffin
granules.
In human, 80% of chromaffin granules contain
adrenalin & 20% of granules contain nor adrenaline.
5. SYNTHESIS OF HORMONES
The pathway of catecholamine biosynthesis in CNS,
sympathetic post ganglionic neurons & adrenal
chromaffin tissue appear to be identical.
The number of steps in each pathway however,
depend on the definite product – dopamine(DA),
adrenalin(E), nor adrenalin(NE)
7. STORAGE & RELEASE
Catecholamines are stored within granules
wherein they are complexed with ATP & specific
protein chromogrannin & DBH.
The secretory vesicles are released through a
stimulus-secretion coupling requiring calcium.
All the contents are released during vesicular
exocytosis.
8. DURATION OFACTION
The NE secreted directly into a tissue remain only
for a few second, that its uptake & diffusion away
from the tissues are rapid.
The NE & E secreted into the blood remain active
until they diffuse into some tissue, where they can
be destoyed by catechol-O-methyl transferase,
this occur mainly in liver.
Therefore when secreted into blood, NE & E
remain active for 10-30 sec
9. MECHANISM OFACTION
Action of E & NE are executed by binding with
receptors called adrenergic receptors, which are
present in the target organs.
Adrenergic receptors are of 2 types:
1. α adrenergic receotor
2. β adrenergic receptor
Circulating E & NE have similar effects of
sympathetic stimulation.
effect of adrenal hormones is prolonged 10 times
more than that of sympathetic stimulation.
10. It is because of slow inactivation, slow degradation
& slow removal of these hormones.
Effect of E & NE on various target organ depend
upon the type of receptors present in the cells of
target organ.
E acts through both α & β receptors equally.
NE acts mainly through α receptors & occassionaly
through β receptors.
11. FACTORS THAT CONTROLSECRETION
Position of individual (standing increases NE secretion)
Exercise
Cigarette smoking
Hypoglycemia
Ketoacidosis
Anesthesia
Surgery (both E & NE secretion)
The release of NE is controlled by the actvation of α2
receptors of the presynaptic memberane, this stimulation
inhibits the release of NE. This mechanism is used by
certain drugs to treat hypertension.
12. METABOLISM OF CATECHOLAMINES
85% of NE is taken by the sympathetic adrenergic neurons.
Remaining 15% of NE & E is degraded.
Adrenaline Nor adrenaline
Meta adrenaline Meta nor adrenaline
VMA
13. Methylation of adrenaline & nor adrenaline is to
meta nephrines (meta adrenaline & meta nor
adrenaline) is by catechol-o-methyl transferase
(COMT).
Oxiadation of metanephrines into vanillyl mandelic
acid (VMA) is by mono amine oxidase (MAO).
14. FUNCTIONS
E increases BMR, so called cholinergic hormone.
E increases oxygen consumption & carbondioxide
removal.
E increases glucose level in blood by increasing
glycogenolysis in liver & muscle.
E decreases coagulation time.
E has stronger effect on heart than NE, it increases
overall activity of heart.
NE has strong effects on blood vessels, causes
constriction of blood vessels. So it is called general
vasoconstrictor.
E increases the rate & force of respiration
