Hormone in Animals


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  • T 4 and T 3 are very similar molecules… T 4 is also called thyroxine ; it contains 4 iodine atoms in it. T 3 (triiodothyronine)only has 3 iodine atoms in it. Iodine is not commonly found in our bodies within molecules. Iodine atoms tend to make ionic, not covalent, bonds in aqueous solutions. That’s why it may seem new to you to find this element in thyroxine and triiodothyronine. Because we don’t need a lot of iodine in our bodies, when we do get it, we need to use it to make these hormones. If we don’t get iodine in our diets, we simply can’t make these hormones. The salt we put on food has the chemical formula: NaCl. It used to be that this salt was sold in its pure form in stores. Also, some people were deficient in iodine in their diets, and health problems were discovered in those people. But now we can buy “iodized salt” in the supermarket. Iodized salt has some iodide ions in it (instead of some of the Cl ions). Ever since manufacturers started including iodide ions in our salt, people have been able to get their required levels of iodine in their diets.
  • On this slide, some serious thyroid gland problems are described. There are other problems that people have with their thyroid glands that are not as severe… Some people have slight problems with their thyroid gland. If that problem causes too much thyroid hormone secretion, that person is said to have slight hyperthyroidism, and has increased metabolism. More often we hear of cases of slight hypothyroidism, where a person’s thyroid gland does not produce enough thyroid hormone… this causes a decreased metabolism, and often weight gain. People with slight hypothyroidism can usually take thyroid hormone as a medication to compensate for their naturally-occurring low levels.
  • The gonads (reproductive glands) are quite complicated. They do have an important endocrine role, but we cannot delve into that in this unit. You will learn all about their role when we do the reproductive system!
  • Hormone in Animals

    1. 1. Body Regulation Endocrine Systems
    2. 2. <ul><li>Principles of Endocrine Control </li></ul><ul><li>- endocrine glands: ductless glands secreting chemical messengers ( hormones ) which diffuse directly into blood and carried to target organs to exert a specific physiological effects </li></ul>
    3. 3. <ul><li>Nervous co-ordination gives rapid control. </li></ul><ul><li>Endocrine co-ordination regulates long-term changes. </li></ul><ul><li>The two systems interact in a dynamic way in order to maintain the constancy of the animal's internal environment, while permitting changes in response to a varying external environment. </li></ul><ul><li>Both systems secrete chemicals , the nervous system as a transmitter between neurones and the endocrine system as its sole means of communication between various organs and tissues in the body . . </li></ul>
    4. 4. <ul><li>Chemistry of Hormones </li></ul><ul><li>Steroids - oestrogen, progesterone, testosterone, cortisone, aldosterone </li></ul><ul><li>Polypeptides (less than 100 amino acids) - oxytocin , insulin , glucagon , antidiuretic hormone (vasopressin) </li></ul><ul><li>Amines - adrenaline, noradrenaline, thyroxine </li></ul><ul><li>Proteins - prolactin, follicle stimulating hormone, luteinizing hormone, thyroid stimulating hormone, adrenocorticotrophic hormone, growth hormone </li></ul>
    5. 6. <ul><ul><li>Pituitary gland - The “ master ” endocrine gland. Controls other endocrine glands </li></ul></ul>
    6. 7. The Hypothalamus & the Pituitary Gland-- Master Endocrine Glands! <ul><li>The Hypothalamus: </li></ul><ul><li>Located in the brain, this region controls most endocrine secretions </li></ul><ul><li>Mainly regulatory hormones are released here. Most control the pituitary gland </li></ul><ul><li>The Pituitary Gland </li></ul><ul><li>Descending from the hypothalamus, this gland has two halves: anterior & posterior </li></ul><ul><li>The anterior half secretes mainly regulatory hormones </li></ul><ul><li>The posterior half secretes hormones, but manufactures none </li></ul>
    7. 8. The Posterior Pituitary Lobe <ul><li>No hormones are made here. They are made in the hypothalamus and just released here. </li></ul><ul><li>Two peptide hormones are released from the posterior pituitary lobe (the neurohypophysis) : </li></ul><ul><li>ADH (antidiuretic hormone or vasopressin) </li></ul><ul><li>OT (oxytocin) </li></ul>
    8. 9. Function of Posterior Pituitary Lobe Hormones <ul><li>ADH  osmoregulation </li></ul><ul><li>as an “antidiuretic,” ADH decreases urine formation by having kidneys conserve water </li></ul><ul><li>also can contract smooth muscle cells, as found in blood vessels-- this causes an increase in blood pressure </li></ul><ul><li>ADH release triggered by osmoreceptors and inhibited by stretch receptors in blood vessels </li></ul><ul><li>OT : </li></ul><ul><li>In females, contracts the uterine wall smooth muscles </li></ul><ul><li>In females, helps to eject milk when lactating </li></ul><ul><li>No known function in males, although in both males and females, OT can have some antidiuretic effects </li></ul>
    9. 10. Lactation <ul><li>In females, PRL promotes milk synthesis </li></ul><ul><li>Milk release is stimulated by oxytocin </li></ul><ul><li>Milk contains an inhibitory peptide to stop lactation when not required. </li></ul><ul><li>In males, PRL decreases LH secretion (note that too much PRL would then decrease androgen levels and cause sterility) </li></ul>       
    10. 14. Hormones secreted by the Hypothalamus & Anterior Pituitary Gland <ul><li>Hypothalamus Anterior Pituitary </li></ul><ul><li>GHRH (GH-releasing) GH (growth hormone) </li></ul><ul><li>SS (somatostatin, GH-inhib) “ </li></ul><ul><li>CRH (corticotropin-rel) ACTH (adrenocorticotropic) </li></ul><ul><li>GnRH (gonadotropin-rel) LH (luteinizing hormone) </li></ul><ul><li>“ FSH (follicle-stimulating) </li></ul><ul><li>PRH (PRL-releasing) PRL (prolactin) </li></ul><ul><li>PIH (PRL rel-inhibiting) “ </li></ul><ul><li>TRH (thyrotropin-rel) TSH (thyroid stimulating) </li></ul>       
    11. 15. What do these anterior pituitary hormones do? <ul><li>Growth Hormone : </li></ul><ul><li>stimulates cells to grow and divide </li></ul><ul><li>increases amino acid transport rate and protein synthesis </li></ul><ul><li>increases fat metabolism </li></ul><ul><li>Typically, GH is secreted during sleep. </li></ul><ul><li>GH secretion increases when malnourished </li></ul><ul><li>GH influences bone growth via somatomedin: </li></ul><ul><li>GH in blood </li></ul><ul><li>GH arrives in liver </li></ul><ul><li>liver secretes somatomedin </li></ul><ul><li>cartilage divides </li></ul><ul><li>bones grow! </li></ul>
    12. 16. <ul><li>Hormones of the complex </li></ul><ul><ul><li>releasing hormones of the hypothalamus </li></ul></ul><ul><ul><ul><li>TSHr </li></ul></ul></ul><ul><ul><li>ant. pituitary hormones: thyrotropin </li></ul></ul><ul><ul><li>thyroxine </li></ul></ul>How are hormones regulated? Hypothalamus-Pituitary-Thyroid Negative Feedback Thyroid
    13. 17. Click for animation
    14. 19. <ul><li>thyroid </li></ul><ul><ul><li>thyroxine (T 4 ), triiodothyronine (T 3 ) </li></ul></ul><ul><ul><ul><li>increase oxidative metabolism </li></ul></ul></ul><ul><ul><ul><li>protein distribution and metabolism </li></ul></ul></ul>Hormones of the thyroid
    15. 20. About the Thyroid Hormones... <ul><li>T 3 and T 4 : </li></ul><ul><li>Function: metabolism regulation (break down carbohydrates and fats, synthesize proteins) </li></ul><ul><li>Can only be made by follicular cells when iodides are available </li></ul><ul><li>Somewhat hydrophobic and get carried by proteins in the blood. </li></ul><ul><li>T 3 more effective, T 4 more abundant </li></ul>
    16. 21. Problems with the Thyroid Gland <ul><li>Hyperthyroidism : </li></ul><ul><li>high metabolic rate, hyperactivity, sensitivity to heat, protruding eyes </li></ul><ul><li>Grave’s disease : when hyperthyroidism is due to an autoimmune problem (TSH is mimicked by autoantibodies) </li></ul><ul><li>Hypothyroidism : </li></ul><ul><li>in the adult: low metabolic rate, sensitivity to cold, sluggishness </li></ul><ul><li>in an infant: cretinism -- stunted growth, mental retardation, abnormal bone formation </li></ul><ul><li>goiter : no T3 and T4 can be made because not enough iodides were ingested. </li></ul>
    17. 22. <ul><ul><ul><li>Goiter - without iodine, functional hormones cannot be made. Lack of iodine in our diet can lead to enlargement of thyroid gland (goiter) Uncommon in U.S. because of iodized salt </li></ul></ul></ul>
    18. 23. <ul><ul><li>Pancreas - Produces insulin and glucagon </li></ul></ul><ul><ul><ul><li>1. Regulates the metabolism of glucose (sugar) </li></ul></ul></ul><ul><ul><ul><li>2. Insulin decreases sugar and glucagon increases glucose levels. </li></ul></ul></ul><ul><ul><ul><li>3. Diabetes mellitus - condition where there is an undersecretion of insulin. Results in high level of glucose in blood. </li></ul></ul></ul>
    19. 24. <ul><ul><li>Adrenal Glands - pyramid-shaped structures that sit on kidneys </li></ul></ul><ul><ul><li>1. Produces adrenaline (also called epinephrine) released during “fight or flight” situations </li></ul></ul><ul><ul><li>2. Increases blood glucose level, heart rate. </li></ul></ul>
    20. 25. Hormones of the Adrenal Glands <ul><li>Adrenal Medulla produces two hormones that regulate the “fight or flight” response </li></ul><ul><ul><li>adrenalin (epinephrine) </li></ul></ul><ul><ul><li>noradrenalin (norepinephrine) </li></ul></ul>
    21. 26. Hormones of the Adrenal Glands <ul><li>Adrenal Cortex produces many hormones </li></ul><ul><ul><li>steroids </li></ul></ul><ul><ul><ul><li>glucocorticoids (cortisol, corticosterone, cortisone) </li></ul></ul></ul><ul><ul><ul><ul><li>cause a rise in blood sugar </li></ul></ul></ul></ul>
    22. 27. Hormones of the Adrenal Glands <ul><li>Adrenal Cortex produces many hormones </li></ul><ul><ul><li>steroids </li></ul></ul><ul><ul><ul><li>mineralcorticoids (e.g., aldosterone) </li></ul></ul></ul><ul><ul><ul><ul><li>regulates bp, bv, salt balance, </li></ul></ul></ul></ul>
    23. 28. Other Endocrine Glands <ul><li>Reproductive glands (the gonads): the ovaries and the testes produce sex hormones </li></ul>
    24. 29. <ul><ul><li>Reproductive Glands (the gonads ) </li></ul></ul><ul><ul><ul><li>1. Male gonads ( testes ) produce sperm. Control growth of facial hair, increase body size, deepening of voice, etc. (testosterone) </li></ul></ul></ul>
    25. 30. <ul><ul><ul><li>Female gonads ( ovaries ) produce eggs (ova). Control widening of hips, development of breasts, prepares uterus for arrival of developing embryo (estrogens, progesterone) </li></ul></ul></ul>
    26. 31. Negative Feedback of Hormones <ul><li>Low concentrations of a particular hormone result in increased secretion of that hormone, and when the concentration reaches a certain level, secretion is reduced </li></ul>
    27. 32. Control of the Endocrine System <ul><ul><li>A. Regulated by negative-feedback mechanism that functions to maintain homeostasis </li></ul></ul><ul><ul><li>1. When target tissue responds to hormone- sends chemical back to gland </li></ul></ul><ul><ul><li>2. Gland stops producing hormone </li></ul></ul><ul><ul><li>3. If level of hormone to low- gland signaled to start secretion of hormone again </li></ul></ul><ul><ul><li>B. Automatic and self-regulating </li></ul></ul>
    28. 34. Blood Glucose Regulation by the Pancreas <ul><li>Glucagon : </li></ul><ul><li>It works on the liver to cause the production of glucose via: </li></ul><ul><ul><li>glycogenolysis </li></ul></ul><ul><ul><li>gluconeogenesis </li></ul></ul><ul><li>It is regulated by blood glucose levels directly: </li></ul><ul><ul><li>secreted when blood glucose drops (before next meal) </li></ul></ul><ul><li>Prevents hypoglycemia </li></ul><ul><li>Insulin : </li></ul><ul><li>It works on the liver to remove glucose from the blood via: </li></ul><ul><ul><li>making glycogen </li></ul></ul><ul><ul><li>preventing gluconeogenesis </li></ul></ul><ul><ul><li>increasing glucose transport into cells </li></ul></ul><ul><li>It is also regulated by blood glucose levels directly </li></ul><ul><li>Prevents hyperglycemia </li></ul>Note: glucagon and insulin work in opposition, and their combined effects control blood glucose
    29. 35. Pancreas: Regulation of Glucose <ul><li>Diabetes results from pancreatic malfunction or receptor malfunction </li></ul><ul><ul><li>alpha cells secrete glucagon (release of glucose) </li></ul></ul><ul><ul><li>beta cells secrete insulin (uptake of glucose) </li></ul></ul><ul><li>Balance of glucagon and insulin determine blood glucose levels </li></ul>