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An in-depth look into the adrenal gland, its structure, the different regions and their hormones, the biosynthesis process, and the functions of cortisol and aldosterone. Additionally, it covers disorders such as Cushing's syndrome, Addison's disease, and hypersecretion of aldosterone.
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Adrenal gland Lies above the kidney forms a cap over it. It has 2 regions(T.S) outer cortex (mesoderm) and inner medulla (ectoderm). The cortex hormones are called corticoids or corticosteroids and adrenal hormones are referred as catecholamine's. The cortex shows 3 zones (regions):
Progesterone 17OH pregnenolone 17OH pregnenolone Deoxy corticosterone 17OH progesterone DHEA Corticosterone 11 deoxy cortisol AD ALDOSTERONE CORTISOL
Plasma cortisol level increases during stress. If not controlled can cause derangement in homeostasis and may lead to death. Cortisol also has wound healing power and therefore given in autoimmune diseases. On individual systems:
These androgens cause suppression of feminine characters in females and cause appearance of sexual hair. Also responsible for libido in women. In males if there is a tumor, stimulates the secondary sexual characters like beard and mustache in non pubertal boy. This condition is referred as precautious pseudo puberty (testes is infertile) In females, in same condition at the embryonic stage, under androgen influence develops external genitalia of male. It is referred as female hermophroditism. Control of secretion 1. Of cortisol:
Adrenal virilism: Due to the tumor in the zona reticularis region. Symptoms: Hirsutism (unwanted male-pattern hair growth on a woman’s face, chest and back) It results from excess male hormones, called androgens. ADRENAL MEDULLA: The term catecholamines generally refer to Adrenaline, Nor adrenaline and dopamine. Neurons may be adrenergic, nor adrenergic and dopaminergic. NA acts as a chemical transmitter at post ganglionic sympathetic nerve terminals and some regions within the brain.
Medulla has granules stained by chromaffin salts, hence called chromaffin cells. Also contains ATP and neuropeptides, and its secretion is stimulated by acetyl choline, released from post ganglionic neurons. Bio synthesis of medullary hormones: Phenyl alanine PAH Alpha tyrosine Ty.Hyd Dihydro phenyl alanine (DOPA) De carboxylation Dopamine B dop. Hyd Nor adrenaline PNMT Adrenaline (80%) So NA is synthesised by hydroxylation and decarboxylation of Phenyl alanine and Adrenaline by methylation of NA.
CNS: In small doses it stimulates the reticular activity and in large doses inhibits the spinal reflexes
Metabolism: Adrenaline has lipolytic action (FFA ) Increases blood sugar level by glycogenolysis, in liver glycogen is converted to glucose by adrenaline.
Uterus: Adrenaline inhibits uterine contraction, where as NA stimulates uterine contraction.
On blood: Adr. Decreases clotting time by acting on V th factor, also causes temporary increase in RBC/WBC/Hb counts.
Skin: Adrenaline causes sweating in humans. But in animals sweating is cholinergic. Adrenaline contracts the erector pilorus muscle (hair straightens) in cold.
On GIT: Causes the relaxation of intestinal muscles and contracts sphincters.
Disorders: Phaeochromacytoma: Hyper secretion of the hormone due to tumor in the medulla All actions are exagerated, severe hypertension is the charecteristic symptom. BP above 180mmhg, HR increases, palpitation (abn. awareness of beating of heart) and sweating Response to stress: When body is in stress, homeostatic disturbances occur. Stress may be due to exercise, fasting, fight, infections, disease, emotions etc., To restore stress it operates two responses namely short term and long term response. Short term response is known as preparing for fight or flight which is moderated by sympathetic system. In long term stress ACTH stimulates cortisol & aldosterone pathway (prolonged action).