The following points highlight the functions of various types of adrenal medullary hormones.
Adrenal Medullary Hormones # Function of Epinephrine:
1. On carbohydrate metabolism:
(a) May stimulate gluconeogenesis in liver by acting as an inducer for key gluconeogenic enzymes like pyruvate carboxylase, G-6-phosphatase etc.
(b) Stimulates glycogenesis in muscle tissue.
(c) It reduces glycogenolysis.
2. On protein metabolism:
It may decrease the release of amino acids from skeletal muscles.
3. On fat metabolism:
(a) It increases lipolysis in adipose tissue, thus free fatty acids help to provide energy.
(b) It mobilizes fat from depot by enhancing lipase action.
(c) It increases cAMP that activates hormone sensitive lipase for lipolysis.
4. On heart:
(a) Increases the heart rate and cardiac output.
(b) Increases the excitability of myocardium.
5. On blood vessel:
(a) Helps in dilation of coronary vessel.
(b) Helps in constriction of somatic blood vessels.
6. On blood pressure:
It increases the systolic blood pressure but no effect on diastolic pressure.
7. On respiration:
(a) Helps in relaxation of bronchial muscle, causing dilation of bronchioles.
(b) O2 consumption rises by 20-40%.
8. On skeletal muscle:
Excitability and contractibility are increased.
9. On smooth muscle:
(a) Helps in contraction of smooth muscles of intestine, gall bladder and spleen.
(b) May cause dilation of muscles in urinary bladder and pupil of eye.
10. On blood:
(a) Number of RBC, WBC and platelets are increased.
(b) Percentage of Hb is raised.
(c) Causes increase in blood sugar.
11. On adenohypophysis:
Stimulates for secretion of ACTH, which in turn helps in secretion of glucocorticoids.
12. On kidney:
(a) Increases urine volume due to constriction of efferent renal arterioles only.
(b) Overproduction may cause constriction of both afferent and efferent renal arterioles and result is the reduction of urine volume.
13. On skin:
Causes contraction of muscles and may help in erection of body hairs and porcupine’s spine.
14. On CNS:
High dose diminishes muscle tone and synaptic reflex.
15. On GI tract:
(a) It inhibits the gastric and intestinal glands.
(b) It also inhibits peristaltic movement.
16. On salivary gland:
It stimulates the more secretion of salivary juice.
17. On gall bladder:
It causes contraction of gall bladder and helps in the expulsion of the bile.
18. On sweat gland:
Causes sweating in mammals.
Adrenal Medullary Hormones # Functions of Nor-Epinephrine:
1. On heart:
(a) Slightly increases the heart rate
(b) No change or slightly change on cardiac output.
2. On blood vessel:
(a) Helps in vasodilation of coronary vessels.
(b) Helps in vasoconstriction of blood vessels in limb, skeletal muscles, liver, kidney etc.
3. On blood pressure:
It increases the systolic, diastolic and arterial blood pressure.
4. On blood:
(a) Has no effect on blood cell count.
(b) Increases blood sugar.
5. On respiration:
(a) Increases the rate and depth of respiration.
(b) O2 consumption is also increased.
6. On kidney:
(a) Causes constriction of renal vessels.
(b) Decreases urine volume.
7. On smooth muscles:
(a) May cause contraction of muscles of intestine, gall bladder and spleen.
(b) Helps in dilation of pupil of eye.
(c) Helps in dilation of urinary bladder muscle.
8. On carbohydrate metabolism:
(a) Blood sugar is slightly increased.
(b) May inhibits insulin secretion.
(c) Increases glycogenolysis.
9. On fat metabolism:
It stimulates lipolysis and increases fatty acid concentration in blood.
10. On sweat gland:
Causes sweating in mammals.