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Endocrine system contd….
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):
- Zona glomerulosa: cells form arched loops consisting of rounded cells. It secretes aldosterone
- Zona fasciculata: consists of long and stright cords of cells appear as bundles. It secretes cortisol
- Zona reticularis: consists of chords of cells, branched freely forming a network. It secretes secretes adrenal androgens namel DHEA & AD.
- (^) Biosynthesis of hormones:
Cells of the cortex are rich in ascorbic acid and
cholesterol
Cholesterol
Pregnenolone
Progesterone 17OH pregnenolone 17OH pregnenolone Deoxy corticosterone 17OH progesterone DHEA Corticosterone 11 deoxy cortisol AD ALDOSTERONE CORTISOL
- (^) Mineral: Causes the drainage of calcium ions, there by decreases blood calcium levels ANTI INFLAMMATORY EFFECTS: Major effects of cortisol which reduces inflammation are
- Reduce the release of vaso active peptides there by reducing vaso dilation and exudate formation in the inflamed region
- Migration of leucocytes from the capillaries to the tissues in the inflamed region is suppressed
- It reduces the antibody formation and stabilises the lysosomal membrane
- Decreases the mast cells to inhibit the release of histamines. Therefore it is used against many non bacterial inflammations and allergic disorders like asthma and eczema.
ANTI STRESS ACTIVITY:
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:
- CVS: Cortisol increases blood pressure, heart rate (salt retention) and increases the capillary fragility
- CNS: Cortisol in large doses cause euphoria
- Bone: Cortisol causes the drainage of calcium ions, so excess hormone may cause osteoporosis.
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:
- Negative feed back mechanism
- Hypothalamus (releasing hormone)
- Circadium rhythm (more in the morning)
- Stress
- Of aldosterone: Renin angiotensin sysytem (RAS), when renal blood flow decreases (BP low, blood sodium decreases) and renin is secreted Mechanism of action: like steroids Disorders: Hyper secretion results in Cushing’s syndrome Causes a) Basophil adenoma of anterior pituitary b) Tumor in the adrenal cortex c) Oat cell cancer of the lung d) Iatrogenic (illness due to treatment) Symptoms: hypertension (salt retention), obesity (increased lipolysis), hirsutism ( development of mustache and beard) Other symptoms include weight gain, osteoporosis, weak bone and muscles and irregular menstruation Addison’s disease: A disorder in which the adrenal glands donot produce enough hormones
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).
