1-Introduction to Endcrine, diabetes .ppt
Download as PPT, PDF0 likes7 views
endokrin
More Related Content
Similar to 1-Introduction to Endcrine, diabetes .ppt (20)
1-Introduction to Endcrine, diabetes .ppt
- 1. The Endocrine Physiology Introduction to Endocrinology Dr. Khalid Alregaiey
- 2. Endocrine System: Overview • Endcocrinology: It is study of homeostatic functions of substances called HORMONES, that are released from glands called endocrine glands distributed throughout the body. • Hormones: Are secretions of ductless glands that are directly released into the blood stream. They can act on cells in the vicinity or on distant target cells. • Endocrine system – the body’s second great controlling system which influences metabolic activities of cells by means of hormones
- 3. Endocrine System: Overview • Endocrine glands – pituitary, thyroid, parathyroid, adrenal, pineal, and thymus • The pancreas and gonads produce both hormones and exocrine products • The hypothalamus has both neural functions and releases hormones • Other tissues and organs that produce hormones – adipose cells, pockets of cells in the walls of the small intestine, stomach, kidneys, and heart
- 5. Autocrines and Paracrines • Autocrines – chemicals that exert their effects on the same cells that secrete them • Paracrines – locally acting chemicals that affect cells other than those that secrete them • These are not considered hormones since hormones are long-distance chemical signals
- 6. Types of Hormones • Amino acid based – most hormones belong to this class, including: • Amines (Tyrosine: Caecholamines and Thyroid hormones, Tryptophan: Melatonin) • Polypeptide hormones • protein hormones • Steroids – Derived from Cholesterol, gonadal and adrenocortical hormones • Fatty acid derived: Eicosanoids, derived from arachidonic leukotrienes and prostaglandins
- 7. A Structural Classification of Hormones
- 8. Correlation of Plasma Half-Life & Metabolic Clearance of Hormones with Degree of Protein Binding Hormone Protein binding (%) Plasma half-life Metabolic clearance (ml/minute) ) Thyroid Thyroxine Triiodothyronine Steroids Cortisol Testosterone Aldosterone Proteins Thyrotropin Insulin Antidiuretic hormone 99.97 99.7 94 89 15 little little little 6 days 1 day 100 min 85 min 25 min 50 min 8 min 8 min 0.7 18 140 860 1100 50 800 600 MCR = (mg/minute removed)/(mg/ml of plasma) = ml cleared/minute
- 9. Circulating Transport Proteins Specific Corticosteroid binding globulin (CBG, transcortin) Thyroxine binding globulin (TBG) Sex hormone-binding globulin (SHBG) Nonspecific Albumin Transthyretin (prealbumin) Principle Hormone Transported Cortisol, aldosterone Thyroxine, triiodothyronine Testosterone, estrogen Most steroids, thyroxine, triiodothyronine Thyroxine, some steroids Transport Protein
- 10. Determinants of Free Hormone Receptor Binding Carrier-bound hormone Endocrine cell Free Hormone Hormone receptor Hormone degradation Biological effects
- 11. Hormone Action • Hormones alter target cell activity by one of the following mechanisms: • Ion Channel–Linked Receptors. • G Protein–Linked Hormone Receptors. • Enzyme-Linked Hormone Receptors. • Intracellular Hormone Receptors and Activation of Genes (steroid and thyroid hormones)
- 12. • Hormones circulate to all tissues but only activate cells referred to as target cells • Target cells must have specific receptors to which the hormone binds Hormone Action
- 13. Location of receptors: • 1. In or on the surface of the cell membrane. The membrane receptors are specific mostly for the protein, peptide, and catecholamine hormones. • 2. In the cell cytoplasm. The primary receptors for the different steroid hormones are found mainly in the cytoplasm. • 3. In the cell nucleus. The receptors for the thyroid hormones are found in the nucleus and are believed to be located in direct association with one or more of the chromosomes.
- 14. • Hormone (first messenger) binds to its receptor, which then binds to a G protein • The G protein is then activated as it binds GTP, displacing GDP • Activated G protein activates the effector enzyme adenylate cyclase • Adenylate cyclase generates cAMP (second messenger) from ATP • cAMP activates protein kinases, which then cause cellular effects Cyclic Adenosine Monophosphate (cAMP) Second Messenger Mechanism
- 15. Cyclic Adenosine Monophosphate (cAMP) Second Messenger Mechanism
- 16. • Hormone binds to the receptor and activates G protein • G protein binds and activates a phospholipase enzyme • Phospholipase splits the phospholipid PIP2 into diacylglycerol (DAG) and IP3 (both act as second messengers) • DAG activates protein kinases; IP3 triggers release of Ca2+ stores • Ca2+ (third messenger) alters cellular responses Cell Membrane Phospholipid: Second Messenger System
- 17. Cell Membrane Phospholipid: Second Messenger System
- 18. Cytokine Receptors & Tyrosine Kinase Receptors
- 19. The Insulin Receptor & Mechanisms of Insulin Action
- 20. Protein Hormones - Mechanisms of Action Adenylyl Cyclase Mechanism Guanylate Cyclase Mechanism Tyrosine Kinase/Cytokine Receptor Mechanism Phospholipid Mechanism ACTH LH FSH TSH GHRH Somatostatin ADH (V2 receptor) HCG MSH CRH Calcitonin PTH Glucagon GnRH TRH PTH Angiotensin II ADH (V1 receptor) Oxytocin ANP Insulin IGF-1 GH Prolactin
- 21. • Steroid hormones and thyroid hormone diffuse easily into their target cells • Once inside, they bind and activate a specific intracellular receptor • The hormone-receptor complex travels to the nucleus and binds a DNA-associated receptor protein • This interaction prompts DNA transcription to produce mRNA • The mRNA is translated into proteins, which bring about a cellular effect Steroid and Thyroid Hormones
- 22. Steroid & Thyroid Hormones - Mechanism of Action
- 23. • Target cell activation depends on three factors • Blood levels of the hormone • Relative number of receptors on the target cell • The affinity of those receptors for the hormone • Up-regulation – target cells form more receptors in response to the hormone • Down-regulation – target cells lose receptors in response to the hormone Target Cell Activation
- 24. • Hormones circulate in the blood in two forms – free or bound • Steroids and thyroid hormone are attached to plasma proteins Hormone Concentrations in the Blood
- 25. • Concentrations of circulating hormone reflect: • Rate of release • Speed of inactivation and removal from the body • Hormones are removed from the blood by: • Degrading enzymes • The kidneys • Liver enzyme systems Hormone Concentrations in the Blood
- 26. • Three types of hormone interaction • Permissiveness – one hormone cannot exert its effects without another hormone being present • Synergism – the total effect of two hormones together is greater than the sum of their individual effects • Antagonism – one or more hormones opposes the action of another hormone Interaction of Hormones at Target Cells
- 27. PLASMA GH ( G/L) CLOCK TIME PLASMA CORTISOL (nmol/L) Hormonal Rhythms 0 4 8 12 8 12 16 20 0 4 8 0 100 200 300 400 500 8 12 16 20 0 4 8
- 28. • Blood levels of hormones: • Are controlled by negative and positive feedback systems • Vary only within a narrow desirable range • Hormones are synthesized and released in response to humoral, neural, and hormonal stimuli Control of Hormone Release
- 29. • Negative feedback is most common: for example, LH from pituitary stimulates the testis to produce testosterone which in turn feeds back and inhibits LH secretion • Positive feedback is less common: examples include LH stimulation of estrogen which stimulates LH surge at ovulation Feedback Control
- 30. Feedback Mechanisms Endocrine cell Target cell _ + Biological effects Endocrine cell Target cell + + Biological effects Negative Feedback Positive Feedback
- 32. Measurement of Hormone Concentrations • Radioimmunoassay (RIA) • Enzyme-Linked Immunosorbentm Assay (ELISA)