The document summarizes the hormones secreted by the adrenal medulla, including epinephrine and norepinephrine. It discusses the control of secretion of these hormones through the sympathetic nervous system and in response to stress. It also outlines the metabolism, receptors, physiological effects, and role in carbohydrate and fat metabolism of the catecholamine hormones.

1. ADRENAL
MEDULLA

2. ADRENAL MEDULLARY HORMONES
Hormones secreted by adrenal medulla:
• Adrenal hormones are released by two types of
chromaffin cells.
• One type of cells secrete norepinephrine and
other type of cells secrete epinephrine.
• These hormones are stored in the form of
chromaffin granules.
• In human, 80% of chromaffin granules contain
epinephrine and 20% of granules contain
norepinephrine.
• These two hormones also called catecholamine.

5. Control of secretion of ad. medullary
hormones:
• Ad. Medulla is innervated by preganglionic
sympathetic nerves emerging mainly from
lower thoracic segments of ipsilateal
intermediolateral grey column of the spinal
cord.
• the main physiology stimulus for release of
hormones is acetylcholine from preganglionic
sympathetic nerve endings innervating the
chromaffin cells.
• Acetylcholine depolarizes the chromaffin cells
which results into ca++ influx and release of
catecholomins into the blood by exocytosis.

6. • Gland is also activated in response to stress
called the flight or flight reaction.
• The following factors also stimulate
sympathetic nervous system and also adrenal
medulla to release catecholamine;
fear, anxiety, pain, trauma, haemorrhage, fluid
loss, asphyxia, hypoxia, severe hypoglycaemia.
• During hypoglycaemia ad. gland stimulated
independently. Also anger state of anxiety
stimulate the gland independently.

7. Metabolism of catecholamines:
• The half-life of catecholamines after entering
the circulation is about 2 minutes.
• 85% of noradrenaline is taken up by the
sympathetic adrenergic neurons.
The biological inactivation (degradation) and
removal of remaining 15% of noradrenaline
and adrenaline occurs in the following
manner.

8. 1. Adrenaline is methoxylated into meta-
adrenaline. Noradrenaline is methoxylated into
meta-noradrenaline.
The methoxylation occurs in the presence of
‘Catechol-O-Methyltransferase’ (COMT). Meta-
adrenaline and meta – noradrenaline are
together called metanephrines.
2. Then, oxidation of metanephrines into
vanillylmandelic acid (VMA) occurs by
monoamine oxidase (MAO).

9. 3. Catecholamines are removes from body
through urine in three forms:
i. 50% as free or conjugated meta – adrenaline
and meta – noradrenaline.
ii. 35% as VMA.
iii. Remaining 15% as free adrenaline and free
noradrenaline.

11. Adrenergic receptors:
1. Alpha receptors; are activated by both
epinephrine and norepinephrine and are
mostly associated with excitatory functions
of the body.
2. Beta receptors; respond to mainly
epinephrine and are associated mainly with
inhibitory functions.

12. Physiological effects of catecholamine
through alpha and beta receptors:
Effects of catecholamine are the same as those
of sympathetic stimulation except that effects
are of longer duration and produced on the
tissues which are not innervated by
sympathetic nerves.

13. Effects of catecholamines through alpha
receptors:

14. Effects of catacholamines through beta
receptors:

15. Effects of catechol. on carbohydrate
metabolism:
• Metabolic effects of catechol. are mainly
through epinephrine. Norepinephrine has
little effect.
1. Effect on liver;
a) Glycogenolysis in liver – epinephrine
increases glycogenolysis in liver via Ca2++
activated glycogen phosphorylase and inhibition
of glycogen synthesis. This causes increase in
blood glucose level.

16. b) Epinephrine also increases glucose
production from lactate amino acid and
glycerol which are glucogenic substances.
2. Effect on muscles;
Epinephrine stimulate glycogenolysis in
muscles by beta adrenergic receptors
mechanism involving stimulation of adenyl
cyclase and cyclic AMP induced stimulation
of glycogen phosphorylase.

17. 3. Effects of epinephrine on fat metabolism;
• Ep. Stimulates lipolysis by activating triglyceride
lipase via beta adrenergic receptors.
• Also mobilizes free fatty acids stored in adipose
tissue supplying substrate for ketogenesis in liver.
• Acetoacetate and beta hydroxybutyrate formed are
transported from liver to peripheral tissues and are
utilized for energy purpose.
• Cardiac muscle (specially) uses FA and acetoacetate
in preference to glucose for energy purpose.
• Resting skeletal muscle also uses fatty acids.

18. Difference in the action of epin. And norepi:
• Epi. has a greater effect on cardiac stimulation
because of its greater effect in stimulating beta
receptors.
• Epi. causes weaker constriction of blood vessels
compared to strong vasoconstriction caused by
norepi.
• Due to its strong vasoconstriction effect, norepi.
is given in case of shock to increase BP.
• Epi. has 5 to 10 times greater metabolic effects as
compared to metabolic effects of norepi.
• Epi. also increases the metabolic rate of the body
as much as 100% above normal.

19. Regulation of secretion of adrenaline and
noradrenaline:
• Adrenaline and noradrenaline are secreted in
adrenal medulla in small quantities even
during rest.
• During stress conditions, due to
sympathoadrenal discharge, a large quantity
of catecholamines is secreted.
• These hormones prepare the body for fight or
flight reactions.

20. • Catecholamine secretion also increases in:
1. Exposure to cold: During exposure to cold,
adrenaline and noradrenaline are secreted in
large quantities. The catecholamines
significantly increase the muscular activity
and sometimes produce shivering so that,
the body temperature increases.
2. Hypoglycemia: release of catecholamines
increases during hypoglycemia. These
hormones increase the blood sugar level by
inducing glycogenolysis in muscle.

21. Dopamine:
• Dopamine is secreted by adrenal medulla.
• The type of cells secreting this hormone is not
known.
• Dopamine is also secreted by dopaminergic
neurons in some areas of brain particularly,
basal ganglia.
• In brain, this hormone acts as a
neurotransmitter.
• The other physiological functions of circulating
dopamine are not understood clearly.

22. • The injected dopamine produces the following
effects:
1. Vasoconstriction by releasing nor-
epinephrine.
2. Vasodilatation in mesentery.
3. Increase in heart rate via beta receptors.
4. Increase in systolic blood pressure. Dopamine
does not affect diastolic blood pressure.
• Deficiency of dopamine in basal ganglia
produces nervous disorder called
Parkinsonism.

23. Applied physiology pheochromocytoma:
• Pheochromocytoma is a condition
characterized by hypersecretion of
catecholamines.
Cause:
• Pheochromocytoma is caused by tumor of
chromophil cells in adrenal medulla.
• It is also caused rarely by tumor of
sympathetic ganglia (extra adrenal
Pheochromocytoma).

24. Signs and symptoms:
• The characteristic feature of
pheochromocytoma is hypertension.
• This type of hypertension is known as
endocrine or secondary hypertension.
• Other features are:
1. Anxiety
2. Chest pain
3. Fever
4. Head ache
5. Hyperglycemia
6. Metabolic disorders

25. 7. Nausea and vomiting
8. Palpitation
9. Polyuria and glucosuria
10. Sweating and flushing
11. Tachycardia
12. Weight loss
Tests for pheochromocytoma:
• It is detected by measuring metanephrines
and vanillylmandelic acid in urine and
catecholamines in plasma.

26. The end