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hormones final.pptx

  1. Hormone Substances released by an endocrine gland and transported through the bloodstream to another tissue where it acts to regulate functions in the target tissue. • Paracrine: Hormones that act locally on cells that did not produce them. • Autocrine: Hormones that act on cells that produced them.
  2. Endocrine Blood vessel Distant target cells Hormone secretion into blood by endocrine gland Paracrine Secretory cell Autocrine Target sites on same cell Adjacent target cell Receptor Hormone or other extra cellular signal
  3. General characteristics of hormones  Hormones are molecules synthesized by specific tissue. Classically these tissues were called glands.  Hormones are secreted directly into the blood which carries them to their sites of action.  Hormones are present at very low levels in the circulatory system.  Hormones specifically affect or alter the activities of the responsive tissue (target tissue).  Hormones act specifically via receptors located on or in, target tissue.
  4. Mechanisms of Hormone Action 1. Fixed Membrane Receptor Mechanism • This type of mechanism is shown by the water-soluble hormones that are amines or proteins in composition such as the growth hormone, oxytocin, ADH, etc. • These hormones can’t pass through the lipid membrane. They have their target receptor on the cell membrane to which the hormone binds. • When the hormone binds to the specific target receptor, the enzyme adenyl cyclase in the cell membrane is activated. This helps in the production of cyclic AMP (cAMP). • cAMP acts as the secondary messenger. It diffuses through the cell membrane and activates several enzymatic reactions to cause biochemical changes. • The target cell responds to these changes and cAMP is deactivated by the enzyme phosphodiesterase.
  5. 2. Mobile Receptor Mechanism • This type of mechanism is shown by lipid-soluble hormones such as steroids that can easily pass through the plasma membrane. • They possess intracellular receptors. The hormones bind to the target receptor that activates the enzymatic activity of the cell to bring about biochemical changes. • Transcription of DNA is initiated by the hormone-receptor complex. • The mRNA is translated into protein. This protein causes biochemical changes inside the cell.
  6. Receptors A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific effect in the cell. Types of receptors 1. Ion channel receptors 2. G-protein coupled receptors 3. Enzyme-linked receptors 4. Nuclear receptors/ intracellular receptors
  7. 1. Ion channel receptors  Ion channel receptors are usually proteins located in the plasma membrane.  Each of these proteins arranges itself so that it forms a passageway or pore extending from one side of the membrane to the other.  These passageways, or ion channels, have the ability to open and close in response to a chemical or mechanical signals.  When an ion channel is open, ions move into or out of the cell. Individual ion channels are specific to particular ions.
  8. 2. G-protein coupled receptors  Present in the membrane. Some part is exposed to the membrane and other is exposed to the cell.  When a drug bind to the outside, the inner surface become open and G-protein is attached to that surface. Fragmentation of G-protein occurs.  Fragmentation leads to the activation of  Adenylyl cyclase enzyme  Phospholipase  cAMP and IP3 are secondary messengers which cause a biological effect.
  9. 3. Kinase linked receptors  Membrane-bound receptor.  Inner surface contains a binding site for the enzyme at which the enzyme gets attached and activated.  Examples include insulin receptors, oxytocin receptors, etc.
  10. 4. Intracellular receptors  Present within the cell such as in the cytoplasm or in the nucleus of the cell.  Drug molecule which acts on the intracellular receptors should be lipophilic so it can cross the cell membrane.  Steroidal hormones such as estrogen hormone act via binding to intracellular receptors.
  11. Hormones Reproduction Growth & Development Maintenance of internal environment Energy production, utilization & storage The four primary arenas of hormone action
  12. Classification of hormones
  13. Polypeptides Steroids Amino acid derivatives Insulin glucagon somatotropin FSH LH Oxytocin Estrogen testosterone cortisol Aldosterone Progesterone Epinephrine norepinephrine Thyroxine, T3 and T4 Melatonin Serotonin
  14. 1. Polypeptide hormones 1. Insulin  Insulin is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the INS gene.  Insulin acts on all cells of the body, binding to receptor proteins on the surface of cells and enabling the uptake of glucose.  Peptide hormones have played an important role in modern medicine including the use of insulin to treat diabetes and the therapeutic application of ACTH and growth hormone.
  15. 2. Glucagon  Glucagon is a peptide hormone, produced by alpha cells of the pancreas.  It raises the concentration of glucose and fatty acids in the bloodstream and is considered to be the main catabolic hormone of the body. 3. Somatotropin  Somatotropin, also known as growth hormone is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in human development.
  16. 5. FSH and LH  Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by a gonadotropin- releasing hormone from the hypothalamus.  In females, an acute rise of LH known as an LH surge triggers ovulation and development of the corpus luteum.  Follicle-stimulating hormone is a gonadotropin, a glycoprotein polypeptide hormone.  FSH is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland and regulates the development, growth, pubertal maturation, and reproductive processes of the body.
  17. 6. Oxytocin  Oxytocin is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary.  It plays a role in social bonding, reproduction and childbirth
  18. 2. Amino acid derivatives 1. Melatonin  The pineal gland in the brain produces melatonin, which is instrumental in your sleep/wake cycles and your internal body clock.  As the light of day becomes the dark of night, your brain amps up your melatonin levels to prepare you for sleep. Interruptions to natural darkness impair melatonin levels and sleep quality. 2. Serotonin (Happy hormone)  Serotonin carries messages between nerve cells in the brain and throughout your body. Serotonin plays a key role in such body functions as mood, sleep, digestion, blood clotting, and sexual desire.
  19. 3. Epinephrine  Epinephrine is released by your adrenal glands in response to stress. This reaction causes a number of changes in your body and is known as the fight-or-flight response.  It is released in high-stress conditions or in excitement or fear. 4. Thyroxine  Produced by the thyroid gland.  controls the rate of metabolic processes (how energy is used) in the body and influences physical development  People may not produce enough of this hormone and get a condition known as hypothyroidism. They can take thyroxine to treat this condition.
  20. 3. Steroidal hormones 1. Aldosterone  Aldosterone (ALD) is a hormone that helps to regulate blood pressure by managing the levels of sodium (salt) and potassium in the blood and impacting blood volume.  Produced by adrenal glands in kidney.
  21. • Where it comes from: ovary (where an egg was released) • Where it acts: uterus • What it does: controls menstruation in women and plays a role in pregnancy. • One of the components of birth control pills
  22. • Where it comes from: testicles • Where it acts: body-hair cells, muscle, reproductive structures • What it does: stimulates development of male sexual characteristics • Testosterone is a steroid and has been administered to athletes in order to improve performance. This is considered to be a form of doping in most sports and is a very dangerous practice. • Females also produce small amounts of testosterone in their ovaries that affect muscle development and other body functions.
  23. • Where it comes from: ovary • Where it acts: breast tissue, reproductive structures in female • What it does: stimulates development of female sexual characteristics • Estrogen levels may be related somehow to migraine headaches in women.
  24. • Where it comes from: outer part of adrenal gland • Where it acts: multiple tissues • What it does: mental stimulation, breaks down fat and protein to glucose, anti-inflammation • It is usually referred to as the "stress hormone" as it is involved in response to stress and anxiety.