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D.5. hormones and metabolism

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My in-class presentation for IB Biology, topic D5. Hormones and Metabolism

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D.5. hormones and metabolism

  1. 1. D.5. Hormones and metabolism Miltiadis-Spyridon Kitsos Platon IB Diploma http://thumbs.dreamstime.com/z/mechanisms-hormone-action-hormones-bind-to- receptors-plasma-membrane-itself-first-messenger-binding-to-40174339.jpg
  2. 2. The official IB Diploma Biology guide Essential idea: Hormones are not secreted at a uniform rate and exert their effect at low concentrations. https://ibpublishing.ibo.org/server2/rest/app/tsm.xql?doc=d_4 _biolo_gui_1402_1_e&part=3&chapter=6
  3. 3. Endocrine glands Endocrine glands secrete hormones directly into the bloodstream Endocrine glands are structures that secrete chemical messages, called hormones, directly into the blood. These messages are transported to specific target cells Types of hormones • Steroids • Proteins • Glycoproteins • Polypeptides • Amines • Tyrosine derivatives http://www.myfirstbrain.com/thaidata/image.aspx?id=1045616 https://upload.wikimedia.org/wikipedia/commons/e/ea/1802 _Examples_of_Amine_Peptide_Protein_and_Steroid_Hormon e_Structure.jpg https://upload.wikimedia.org/wikipedia/commons/e/ea/1802_Exam ples_of_Amine_Peptide_Protein_and_Steroid_Hormone_Structure.j pg http://www.austincc.edu/rfofi/NursingRvw/NursingPics/EndocrinePics/hormonesneurotrans mitters.jpg
  4. 4. The mechanism of action of steroid hormones Steroid hormones bind to receptor proteins in the cytoplasm o•the target cell to •orm a receptor- hormone complex. Steroid hormones can cross directly through the plasma membrane and the nuclear membrane and bind to receptors An example is estrogen. The receptor-hormone complex then serves as a transcription factor, promoting or inhibiting the transcription of a certain gene. http://physiologyonline.physiology.org/content/nips/16/6/251/F1.large.jpg?download=true
  5. 5. The receptor-hormone complex The receptor-hormone complex promotes the transcription of specific genes Transferred to specific target cells Calciferol (steroid)-> binds to specific receptor in nucleus->promotes expression of calbindin (calcium transport protein) -> absorption of calcium from the intestine. http://www.thenutritiondr.com/files/CarbsProFat-Gluconeogenesis.jpg Some steroids, such as cortisol, bind to receptors in the cytoplasm and the receptor-hormone complex then passes through the nuclear membrane into the nucleus to effect transcription.
  6. 6. Cortisol may have different effects in different kinds of cells. The receptor-hormone complex promotes the transcription of specific genes The hormone may have different efects in different cells and it may even have an inhibitory effect. For example, when the steroid hormone cortisol binds to its receptor in the cytoplasm of a liver cell and enters the nucleus it activates many of the genes needed for gluconeogenesis; i.e., the conversion of fat and protein into glucose raising blood glucose. At the same time, it decreases the expression of the insulin receptor gene, preventing glucose from being stored in the cells and also raising blood glucose. In the pancreas, the cortisol receptor complex inhibits the transcription of insulin genes.
  7. 7. Mechanism of action of peptide hormones Peptide hormones bind to receptors in the plasma membrane of the target cell. Protein hormones are hydrophilic so they cannot pass through the membrane directly. Instead they bind to surface receptors that can trigger a cascade reaction mediated by chemicals called second messengers. http://lh5.ggpht.com/- dqtzvTxoQxY/UL1RakaZIQI/AAAAAAAABhc/hgYZcTHFtJE/peptide%252520hormonal%252520a ction_thumb%25255B6%25255D.png?imgmax=800
  8. 8. The role of secondary messengers Binding of hormones to membrane receptors activates a cascade mediated by a second messenger inside the cell Second messengers: small water soluble molecules spread throughout the cells Relay messages Calcium ions and cyclic AMP (cAMP) are the two most common second messengers. See how epinephrine (“fight or flight” hormones) works http://lh5.ggpht.com/- dqtzvTxoQxY/UL1RakaZIQI/AAAAAAAABhc/hgYZcTHFtJE/peptide%252520hormonal%252520a ction_thumb%25255B6%25255D.png?imgmax=800 http://highered.mheducation.com/sites/0072507470/student_view0/chapter17/animation__ second_messenger__camp.html
  9. 9. The role of secondary messengers Binding of hormones to membrane receptors activates a cascade mediated by a second messenger inside the cell +GTP (energy)
  10. 10. The pituitary hormones Hormones secreted by the pituitary control growth, developmental changes, reproduction and homeostasis. http://www.zyropathy.com/wp- content/uploads/2016/10/Pituitary-gland-anatomy.jpg The anterior pituitary synthesizes and secretes a number of hormones that control growth, reproduction and homeostasis. Examples include FSH and LH. The posterior pituitary gland secretes oxytocin and ADH, but these hormones are not produced there. Instead, they are synthesized in unusual cells called neurosecretory cells found in the hypothalamus. The hormones travel down the axons of the neurosecretory cells and are stored at the ends of the axons, until impulses pass down the axons from the hypothalamus, stimulating secretion. http://highered.mheducation.com/sites/0072943696/student_v iew0/chapter10/animation__hormonal_communication.html
  11. 11. The role of the hypothalamus The hypothalamus controls hormone secretion by the anterior and posterior lobes of the pituitary gland 1. The hypothalamus links the nervous system to the endocrine system via the pituitary gland. 1. Both the nervous system and the endocrine system play a role in homeostasis and in the control of other processes including reproduction. 3. The role of the hypothalamus is to secrete releasing factors, which stimulate the secretion of the anterior pituitary gland hormones. The releasing factors are carried from the hypothalamus to the anterior pituitary gland by a portal vein. 4. Negative feedback mechanisms (e.g., ADH) http://image.slidesharecdn.com/ch19lecturepresentation-140913124201-phpapp01/95/dr-b- ch-19lecturepresentation-11-638.jpg?cb=1410612186
  12. 12. Regulation of milk secretion Control of milk secretion by oxytocin and prolactin Prolactin is a hormone produced by the anterior pituitary found During pregnancy, high levels of estrogen increase prolactin production but inhibit the effects of prolactin on mammary glands. The abrupt decline in estrogen and progesterone following delivery removes this inhibition and the production of milk begins. However, the release of the milk after it is produced depends on the hormone oxytocin. Nursing by an infant stimulates the continued creation of prolactin. It also stimulates oxytocin release. Oxytocin stimulates the contraction of cells that surround the structures holding the milk leading to the ejection of the milk. Positive feedback loops http://archive.cnx.org/resources/75a2ecfbb8e17ade7cfcff7595c410a62 49ba2a0/2922_Let_Down_Reflex-new.jpg
  13. 13. Injection of growth hormone by athletes Some athletes take growth hormones to build muscles Growth hormone is another polypeptide hormone produced in the anterior pituitary. The binding of growth hormone to liver cells stimulates the release of insulin-like growth factor which circulates in the blood and stimulates bone and cartilage growth. Additional effects, one of which is increase in muscle mass. While it is clear that it leads to greater muscle mass, the data is not clear that it leads to greater strength. Another claim is that it allows tired muscles to recover more quickly allowing an individual to train harder and more often The scientific research on the topic suggests that the benefits provided in terms of enhanced performance are small or non-existent compared to the risks of injecting the hormone. For this reason, use of the drug is banned by most international sporting federations. https://upload.wikimedia.org/wikipedia/commons/thumb/9/99/Endocri ne_growth_regulation.svg/240px-Endocrine_growth_regulation.svg.png
  14. 14. The negative effects of the use of the human growth hormone Some athletes take growth hormones to build muscles https://lehman-cuny.digication.com/files/M0045c1f4ed6a253aeaf19acc1c695f61.jpg
  15. 15. Eradicating iodine deficiency Cooperation and collaboration between groups of scientists: the International Council for the Control of Iodine Deficiency Disorders includes a number of scientists who work to eliminate the harm done by iodine deficiency. http://wisemensvitamins.com/wp-content/uploads/2010/12/iodine-deficiency-symptoms.jpg Thyroid hormone refers to two similar hormones derived from tyrosine. Triiodothyronine (T3 ) contains three iodine atoms and tetraiodothyronine (T 4 ) contains four iodine atoms. Correct functioning of the thyroid requires iodine in the diet. If there is dietary insufficiency, then there are a number of consequences including a condition known as goiter. https://highered.mheducation.com/sites/9834092339/student _view0/chapter46/mechanism_of_thyroxine_action.html The inability to produce the thyroid hormones because of the absence of iodine means that the hypothalamus and the anterior pituitary continuously stimulate the thyroid and enlargement of the thyroid results. Iodine defciency during pregnancy can affect fetal nervous development and can lead to mental retardation in children.
  16. 16. Eradicating iodine deficiency Cooperation and collaboration between groups of scientists: the International Council for the Control of Iodine Deficiency Disorders includes a number of scientists who work to eliminate the harm done by iodine deficiency.

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