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Endocrine System

Endocrine System. Week 6 Dr. Walid Daoud A. Professor. Endocrine system. It is a slow control system by hormones directly secreted by ductless gland into the blood to exert their effects on distant tissues. Physiological properties of hormones. 1- Small amounts.

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Endocrine System

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  1. Endocrine System Week 6 Dr. Walid Daoud A. Professor

  2. Endocrine system It is a slow control system by hormones directly secreted by ductless gland into the blood to exert their effects on distant tissues.

  3. Physiological properties of hormones 1- Small amounts. 2- Rate of secretion according to body need. 3- Effects on various tissue or specific organ. 4- Initiate biochemical reactions. 5- Some antagonize effects of others. 6- Super-added rhythms.

  4. Chemical nature of hormones 1- Protein and polypeptide hormones: Hypothalamic, pituitary, pancreatic and parathroid hormones. 2- Steroid hormones: Adrenocortical and gonadal hormones 3- Hormones derived from simple amino acids: Thyroid and adrenal medullary hormones.

  5. Hypothalamus 1-Releasing hormones: .Growth hormone releasing hormone (GHRH) .Thyrotropin releasing hormone (TRH) .Corticotropin releasing hormone (CRH) .Gonadotropin releasing hormone (GnRH) 2-Inhibiting hormones: .Somatostatin (SS) .Prolactin inhibiting hormone (PIN)

  6. Pituitary Gland 1-Anterior pituitary hormones: .Growth hormone (GH) .Thyroid stimulating hormone (TSH) .Adrenocorticotropic hormone (ACTH) .Gonadotropins (FSH and LH) .Prolactin 2-Posterior pituitary hormones: .Antidiuretic hormones .Oxytocin

  7. Thyroid Gland . Thyroxine (T4) and T3. . Calcitonin. Parathyroid Gland . Parathormone. Pancreas . Insulin. . Glucagon

  8. Adrenal Gland 1-Adrenal cortex: .Glucocorticoids (cortisol). .Mineralocorticoids (aldosterone). 2-Adrenal medulla: .Epinephrine. .Norepinephrine. Gonads 1-Ovaries: estrogen and progesterone. 2-Testes: testosterone.

  9. Mechanism of Action of Hormones Hormones change the rate of specific activity of target cell by increase activity of certain enzymes. The hormone combine to its specific receptor present on cell membrane or inside the target cell. Hormones are called primary messengers while the chemical substance that result from combination of hormone and receptor inside the cell is called second messengers.

  10. Mechanism of action of protein & polypeptide hormones They produce rapid change in rate of enzyme activity. Receptors present in plasma membrane. 3 messenger systems: 1-Cyclic AMP: Combination of hormone with receptor form cAMP from ATP. cAMP (2nd messenger) which affects transport system in the cell membrane and change activity of certain enzymes.

  11. Mechanism of action of protein & polypeptide hormones 2-Calcium-calmodulin system: Combination of hormone with its receptor lead to increase in calcium ions and its combination with specific protein, calmodulin, activating it. Calcium calmodulin complex (2nd messenger) increases or decreases enzyme activities inside the cell. 3-Membrane phospholipid system: 2nd messengers: diacylglycerol(DAG) and inositol triphosphate (IP3) from membrane phospholipid affects cell enzymes activity.

  12. Mechanism of action of steroid hormones Slower action, stimulate protein synthesis in target cells. Receptors inside cytoplasm of target cells forming hormone - receptor complex (H-R complex) which bind with DNA of chromosomes causing transcription of specific mRNA which diffuses to cytoplasm to initiate protein synthesis.

  13. Mechanism of action of thyroid hormones Slow action as they act through protein synthesis. Hormone combines with specific receptors inside the nucleus forming H-R complex then bind to DNA causing increased or decreased synthesis of certain enzymes that regulate cell function.

  14. Factors regulation of hormone secretion 1-Releasing and inhibiting factors: . Nervous: epinephrine. . Hormonal: hypothalamic hormones. 2-Feedback control: . Hormone-hormone feedback. . Substrate-hormone feedback. . Mineral-hormone feedback.

  15. Pituitary Gland A small gland at the base of skull. 1-Anterior pituitary gland (adenohypophysis): connected to hypothalamus through hypothalamo-hypophyseal portal vessels. 2-Posterior pitiutary gland ( neurohypophysis): Connected to hypothalamus through a dense tract of nerve fibers, hypothalmo- hypophyseal tract

  16. Growth hormone A protein hormone secreted from anterior pituitary gland, stimulates growth of skeleton and most soft tissues. Actions: 1- On growth. 2- On protein metabolism. 3- On carbohydrate metabolism. 4- On lipid metabolism.

  17. Factors Affecting Growth hormone 1- Factors increasing secretion of GH: Hypothalamus produces GHRH in case of: -Low blood glucose and FFA. -Increased amino acids in blood. -Emotional stress. -Deep sleep. 2- Factors decreasing secretion of GH: Hypothalamus produces GHIH or somatostatin -Increased bood glucose and FFA. -Cortisone.

  18. Disorders of GH secretion 1- GH deficiency (Dwarfism). 2- GH excess: - Gigatism. - Acromegaly.

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