Endocrine system

2. Endocrine system Prepared by Ms. Azra Arif D.A Degree college for woman Phase VIII

3. ENDOCRINE SYSTEM • DEFINITION • Endocrine glands are organs in the body that produce hormones which are released directly into the bloodstream. Together these glands make up the endocrine system, which performs essential functions like regulating metabolism, growth and reproduction.

4. INTRODUCTION • Endocrine derives from the Greek words endo meaning inside, within, and crinis for secrete • Chemicals are released by these glands(hormones) hormonederived from Greek word which means ‘to excite • The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine. • In animals glands are of two types • Exocrine gland: release products (enzymes) into ducts • Ex) Sweat, digestive juices • Endocrine glands:– directly to bloodstream; NO DUCTS • Ex) Hormones • Features of endocrine gland: glands are, in general, their ductless nature, their vascularity, and usually the presence of intracellular vacuoles or granules storing their hormones.

5. Endocrine system vs. nervous system • Endocrine glands • Information signaling system • Effects are slow to initiate • Response are prolonged (few hrs to week) • HORMONES release in blood stream • Nervous system • Information signaling system • effects very fast and quick • Responses are short lived. • NEUROTRANSMITTER travel through neurons release in synaptic cleft

6. CHIMCAL CLASSIFICATION OF HORMONES • Peptide/ Protein • Steroid • Amine derived from single amino acids (tryptophan, tyrosine) 4. Eicosanoid Produced from 20-carbon fatty acid Produced in all cells except RBCs, 2nd messenger ,Prostaglandins and leukotrienes, inflammation PEPTIDE HORMONE • Not lipid soluble • Received by receptors external to the cell membrane STEROID HORMONE • Lipid soluble • Diffuse through cell membranes

7. Hormone Actions • PEPTIDEHORMONE • React with specific receptors outside the cell • This triggers an enzyme reaction with lead to the formation of a second messenger (cAMP). • cAMP can produce specific intracellular functions: • Activates cell enzymes • Change in membrane permeability • Promote protein synthesis • Change in cell metabolism • Stimulation of cell secretions

9. Hormone Actions • SteroidHormones • Pass through the cell membrane • Binds to specific receptors • Then enters the nucleus to bind with the cells DNA which then activates certain genes (Direct gene activation). • mRNA is synthesized in the nucleus and enters the cytoplasm and promotes protein synthesis for: • Enzymes as catalysts • Tissue growth and repair • Regulate enzyme function

11. Effects of hormones • One tissue can respond to many hormones • Synergistic effect- whentwo or more hormoneswork together to produce a result • Example: epinephrine and nor epinephrine have an additive effect to increase heart rate • Permissiveeffect- one hormone enhances the effect of another hormone e .g . Glucocorticoid enhance effectiveness of catecholamine's (epinephrine and nor epinephrine) • Antagonisteffect-one hormone opposes the effect of another • EX: insulin promotes fat formation glucagon promote fat breakdown • Control of hormone release • Endocrine glands are activated by humoral , neural or hormonal stimuli • HORMONE LEVEL INTHE BLOOD CONTROL BY NEGATIVE FEED BACK

12. Endocrine Glands • Hypothalamus • Pituitary • Anterior lobe • Posterior lobe • Thyroid gland • Parathyroid glands • Adrenal Glands • Cortex • Medulla • Islets of Langerhans • Gonads • Ovaries • Testes • Pineal gland • Thymus • others Hormonal Communication

13. Hypothalamus • Neuroendocrine organ • Central part of brain attached by numerous nerves to pituitary gland • Weight is about 4g(human) • Control the pituitary gland by producing chemicals (releasing/stimulating or inhibiting hormones • Maintains homeostasis(heart rate, body temperature, water balance, and the secretions of the pituitary gland)

14. Pituitary gland(Hypophysis) • Pea size gland hang from the base of brain by stalk (infundibulum) loge in the bone of skull, weigh is about 5gm • In past considered as master gland but it itself under the control of hypothalamus • Hypothalamohypophyseal complex(master gland) • consists of a hormone-producing glandular portion • Have two lobes 1.Anterior pituitary (adenohypophysis) 2.Posterior pituitary (Neurohypophysis) .

15. Anterior pituitary –hypothalamus • (Adenohypophysis) • Secretes six regulating hormone(trophic hormone) • Growth / somatotropin hormone (GH) • Thyroid stimulating hormone (TSH) • Adrenocorticotropic hormone (ACTH) • Gonadotropin(Follicle stimulating hormone (FSH) Luteinizing hormone (LH) • Prolactin • Melanocyte stimulating hormone endorphins chemicals that act on the nervous system to reduce sensitivity to pain.

16. Anterior P. Homeostatic Imbalances Growth /SOMATOTROPINhormone (GH) it is a non- trophic,anabolic hormone simulate the growth of all body tissue specially skeletal muscles ,bone and cartilage. Control protein synthesis and general metabolism imbalances Hyperseretion in youth produces gigantism • Hyperseretion in adult produces acromegaly • Hypo secretion in childhood produces pituitary dwarfism

17. Posterior Pituitary or Neurohypophysis • Neurohypophysis • does not synthesize hormones, however, it stores and releases two hormones produced by the neurosecretory cells of the hypothalamus • It is an extension of hypothalamus • ADH • Oxytocin

18. Pituitary—Posterior lobe • Oxytocin • Stimulates smooth muscle contraction of uterus & mammary glands. • AntidiureticH. • Stimulates water reabsorption in collecting ducts. • Stimulates vasoconstriction (vasopressin) Lack  diabetes insipidus ADH • Hypo secretion produces diabetes insipidus “tasteless” • Excessive thirst and urination

19. Thyroid Gland • Location in neck • Bilobed • Inferior to larynx • Anterior & lateral to trachea lobed are connected by thinn connective tissue called isthmus • Weigh about 25-40gm • Composed of follicles • Follicle cells produce • Thyroxin(Tetraiodothyronine(T4)Triiodothyronine (T3) Regulates metabolism and energy balance • Both increase cellular metabolism and use of oxygen ,rise heat production. increase protein synthesis, uptake of glucose Parafollicular/ C cells • Calcitonin • Decreases blood Ca2+ by depositing it in bones

20. Homeostatic imbalances • Hypothyroidism results • Myxedema (in adults)lethargy, gain weight puffiness and thickening of skin • Goiter—low levels of iodine • Cretinism (in children)mental retardation,dwarfism,lack of sexual maturity • Hashimotos disease(injury ,infections ,wrong treatment ,age) • Hyperthyroidism results • Graves disease or basedows disease(enlargement of overall gland along with exopthalamic goiter(excess accumulation of fat and mucus in eye orbit)

21. Parathyroid Glands • Four small glands embedded on the surface of thyroid • Weigh about 0.05g-0.3g • Parathyroid hormone (PTH) • Antagonistic of calcitonin • Stimulated by falling ca in blood and inhibiting by rising blood ca • Stimulates osteoclasts to free Ca2+ from bone • Stimulates Ca2+ uptake from intestine & kidney

22. Parathyroid ;Homeostatic imbalance • Hyperparathyroidism results in hypercalcaemia and all its effects and in extreme bone destructions. • Hypoparathyroidismleads to hypocalcaemia, evidenced by tetany and respiratory paralysis

23. Adrenal gland/ suprarenal gland • Triangular structure located at the top of kidney weigh of each gland is 5gm • Have two parts cortex ,medulla • Adrenal cortex • Produces three kinds of steroid hormones • Glucocorticoid(cortisol) • Mineral corticoid(aldosterone) • Small amount of sex hormone.

24. Adrenal cortex • Cortex • Activity stimulated by ACTH • Controls prolonged responses by secreting corticosteroids. • Glucocorticoid • Cortisol regulate glucose metabolism and the immune system. • Mineral corticoids • Aldosterone regulate salt and water balance • Gonad corticoids • Androgens

25. Adrenal Cortex Imbalances • Hyper secretion leads to Cushing’s disease • ACTH-releasing tumors or side effects of corticoid drugs. • Weight gain • Muscle loss and weakness • Fragile skin • Reduced sex drive • Depression/inability to think clearly • Hypo secretion leads to Addison’s Disease • Deficits in glucocorticoid and mineral corticoid. • Fatigue, weakness, loss of appetite • Muscle and joint pain • Gastrointestinal problems (nausea, vomiting, etc.) • Darkening of the skin on the face, neck, and back of hands • Low blood pressure • A craving for salt

26. Adrenal Medulla • Medulla • The adrenal medulla mediates short–term responses by secreting catecholamine hormones. • Cells are modified neurons (lack axons) • Epinephrine (adrenaline) • Norepinephrine (noreadrenaline) • enable a rapid ( fight-or-flight ) responses to stress by increasing blood glucose and blood pressure and directing blood to the heart, brain, and skeletal muscles.

27. Pancreas • Consists of two major types of secretory tissues which reflects its dual function • Exocrine gland • secretes digestive juice • localized in the acinar cells • Endocrine gland • releases hormones • localized in the islet cells (islets of Langerhans)About a million” embedded in pancreas • Control centers for blood glucose • Insulin from beta cells • Glucagon from alpha cells

28. Pancreas Homeostatic ImbalancesDiabetes • Symptoms: • Polyuria • Polydipsia • Polyphagia Blood Level Regulation in Diabetics

29. Gonads • Ovaries • Estrogens • Progesterone • Testes • Testosterone • Reproductive functions when we study reproductive system.

30. Gonads; homeostatic imbalance OSTEOPOROSIS • Osteoporosis is a condition in which bones become fragile and more likely to break • Many factors like decrease estrogen during menopause in woman. • Decrease in testerone in man due to increase in age. • Fractured bone due to minor fall Polycystic ovary syndrome • more common endocrine system diseases, affecting between 7% to 10% of women aged 15 to 45. • symptoms are irregular menstruation, male hormone excess symptoms like hirsutism (increased and unwanted hair growth) and acne and difficulty to conceive. • have multiple egg-containing cysts on the ovaries. They are higher risk for metabolic complications like diabetes and hypertension.

31. Pineal gland • Located in diencephalon Melatonin(primary hormone) • Melatonin have antigonadotropic effect in humans • Inhibits early puberty • Day/night cycles • Timing of sleep, body temperature, appetite • Secretes melatonin during darkness • Participates in setting the body’s clock • Melatonin is a potent antioxidant • Melatonin is high when young and is reduced as we age

32. Thymus gland • Lymphocytes that pass trough the thymus , transformed into T-cells • thymosins stimulate the development and differentiation of T lymphocytes • play a role in regulating the immune system by stimulating other kinds of immune cells

33. Non-Endocrine Gland Hormones • Stomach (gastrin) • Small intestine (duodenum intestinal gastrin, secretin, cholecystokinin) • Heart (atrial natriuretic peptide) • Kidneys (erythropoietin, rennin) • Adipose tissue (leptin, resistin) • Skin (cholecalciferol) • Placenta (human chorionic gonadotropin, human placental lactogen, relaxin) Developmentofendocrinegland • All derived from three germ layers • Those derived from mesoderm produce steroidal hormone • Others produced amino acid based hormone

34. Others type of signaling Paracrine:a form of cell signaling in which the target cell is near the signal-releasing cell. Autocrine: a form of signaling in which a cell secretes a hormone or chemical messenger (called the autocrine agent) that binds to autocrine receptors on the same cell, leading to changes in the cells Juxtacrine:Juxtacrine signaling is a type of intercellular communication that is transmitted via oligosaccharide, lipid, or protein components of a cell membrane, and may affect either the emitting cell or the immediately adjacent cell Juxtacrine signaling requires physical contact between the two cells involved.