Endocrine System_ST.ppt


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Endocrine System_ST.ppt

  1. 1. Endocrine System By Dr. Shamanthakamani Narendran
  2. 2. Endocrine System The endocrine system is made up of the cells, tissues, and organs that secrete hormones into body fluids
  3. 3. INTRODUCTION <ul><li>Endocrine means ‘ secreting internally’ . </li></ul><ul><li>Indeed, the endocrine system is made up of glands whose secretions enter the blood stream. </li></ul><ul><li>Hence these glands are different from those whose secretions are released on the surface of the body, like the sweat glands or the tear secreting glands. </li></ul>
  4. 4. <ul><li>The endocrine glands are sometimes referred to as ‘ ductless ’ glands. </li></ul><ul><li>This is to differentiate them from another set of glands ( exocrine ). </li></ul><ul><li>Exocrine glands have a duct or tube which carries the secretions to the place where it should act. </li></ul><ul><li>In contrast, the secretions of endocrine glands ( ductless ) enter the blood stream directly. </li></ul><ul><li>These secretions are called hormones . </li></ul>
  5. 5. <ul><li>Characteristically, hormones travel in the blood stream far from the gland which secreted them. </li></ul><ul><li>Hormones act on an organ/structure which is called the target organ . </li></ul>ENDOCRINE GLANDS (DUCTLESS) EXOCRINE GLANDS (WITH DUCT) <ul><li>HORMONE </li></ul><ul><li>BLOOD STREAM </li></ul><ul><li>DISTANT ACTION </li></ul><ul><li>SECRETIONS </li></ul><ul><li>LOCAL ACTION </li></ul>BLOOD VESSEL DUCT
  6. 6. The endocrine system is concerned with the maintenance of homeostasis or internal balance <ul><li>Glands comprising the endocrine system; </li></ul><ul><li>Pituitary  brain </li></ul><ul><li>Thyroid & parathyroid  neck </li></ul><ul><li>Adrenal glands  top of each kidney </li></ul><ul><li>Pancreas  abdomen </li></ul><ul><li>Gonads  pelvis (ovaries & testes) </li></ul><ul><li>Thymus  chest </li></ul><ul><li>Pineal  brain </li></ul>
  7. 8. THE SYSTEM IS LARGELY CONTROLLED BY HYPOTHALAMUS & HENCE IS LINKED TO THE AUTONOMIC NERVES SYSTEM <ul><li>This control mechanism has three levels. </li></ul><ul><li>Hypothalamus </li></ul><ul><li>Pituitary gland </li></ul><ul><li>Other glands (thyroid, adrenals, etc.) </li></ul>
  8. 9. <ul><li>The hypothalamus has many essential functions, one of these is regulation of the endocrine system. </li></ul><ul><li>It controls the endocrine glands through releasing hormones . </li></ul><ul><li>This mechanism regulates the secretions of almost all the other glands. </li></ul><ul><li>Exceptions are: a small part of the pituitary gland, the posterior pituitary , and the pancreas. </li></ul>
  9. 10. <ul><li>The releasing hormones pass (like other hormones) via the blood stream to the pituitary gland which is the next level of control . </li></ul><ul><li>The pituitary (the anterior part ) receives releasing hormones from the hypothalamus. </li></ul><ul><li>In response to these releasing hormones (RH), the pituitary secretes stimulating hormones (SH). </li></ul><ul><li>There is a specific SH for each gland (i.e. separate SH for thyroid/adrenal glands/and for gonads. </li></ul>
  10. 11. <ul><li>The other glands (i.e. thyroid, adrenals, gonads) in response to the specific SH from the pituitary, the gland secretes its hormone. </li></ul><ul><li>These three levels of control can be understood with an example </li></ul><ul><li>First level – hypothalamus: thyrotropin releasing hormone. </li></ul><ul><li>Second level – (ANT) pituitary: TSH </li></ul><ul><li>Third level – thyroid gland: thyroid hormone (thyroxine) </li></ul>
  11. 12. <ul><li>Thus the hypothalamus triggers the pituitary, which in turn triggers the target gland. </li></ul>HYPOTHALAMUS TARGET GLAND (THYROID GLAND) ANTERIOR PITUITARY OTHER STIMULI FEEDBACK (e.g. thyroxine) RH SH
  12. 13. <ul><li>The hormones secreted by the target gland have a ‘feedback effect’ on both the pituitary and the hypothalamus . </li></ul><ul><li>This means if the thyroid gland secretes increased amounts of thyroid hormone, this has a negative feedback effect on both the pituitary and the hypothalamus. </li></ul><ul><li>As a result the amount of stimulating and releasing hormones (SH, RH) decreases . </li></ul><ul><li>Thus further secretion of thyroid hormone is prevented. </li></ul>
  13. 14. <ul><li>This is a very important control mechanism. </li></ul><ul><li>On the other hand, if the target gland secretes less of its hormone, the pituitary and hypothalamus are stimulated to secrete greater amounts of SH and RH respectively. </li></ul><ul><li>The hypothalamus is stimulated by specific factors, both inside and outside the body . </li></ul><ul><li>The stimuli are specific for each target gland. </li></ul>
  14. 15. <ul><li>For example, in presence of cold, the hypothalamus stimulates the pituitary, which activates the target gland. </li></ul><ul><li>Similarly there are specific stimuli which cause the hypothalamus to secrete the specific RH to activate the adrenal glands and the gonads. </li></ul>COLD HYPOTHALAMUS PITUITARY THYROID THYROID HORMONE Increases Metabolism & heat is produced
  15. 16. PITUITARY GLAND <ul><li>Located at the base of the brain. </li></ul><ul><li>It is roughly pea sized, weighting approximately half a gram. </li></ul><ul><li>The pituitary gland has been called the control centre of the endocrine system. </li></ul><ul><li>It is under the control of the hypothalamus. </li></ul><ul><li>There are 3 parts or lobes: Posterior, intermediate, and anterior. </li></ul><ul><li>The intermediate lobe is thinner than the other two, and is still being investigated. </li></ul>
  16. 18. POSTERIOR PITUITARY <ul><li>The lobe stores two hormones. </li></ul><ul><li>The hormones are produced in the hypothalamus. </li></ul><ul><li>Their release is also controlled by the hypothalamus, which sends the necessary nerve messages to the posterior pituitary. </li></ul><ul><li>The two hormones are anti diuretic hormone (ADH) & oxytocin . </li></ul><ul><li>ADH controls the amount of water in the body. </li></ul>
  17. 19. <ul><li>ADH does this by acting on the kidneys, regulating the amount of water they excrete or retain. </li></ul><ul><li>ADH prevents water from being excreted. </li></ul><ul><li>The hypothalamus is stimulated to send a message (RELEASE ADH!) to the pituitary, if blood volume decreases. </li></ul><ul><li>This could happen after severe bleeding or even if we lose a lot of fluid due to diarrhea or vomiting. </li></ul>
  18. 20. <ul><li>OXYTOCIN causes the contractions of the uterus which are necessary for child birth. </li></ul><ul><li>It is also responsible for the release of breast milk. </li></ul><ul><li>Hence the stimuli are factors like the pressure of the infant’s head on the uterus, or near the nipple, during breast feeding. </li></ul><ul><li>The function in men is uncertain. </li></ul>
  19. 21. ANTERIOR PITUITARY <ul><li>Produces the hormones which it secretes (unlike the posterior pituitary). </li></ul><ul><li>Trigger signals to release these hormones, or not is sent by the hypothalamus. </li></ul><ul><li>There are 6 main hormones: Two of them ( growth hormone & prolactin ) act directly on body tissues or processes. </li></ul><ul><li>The other four hormones are Stimulating Hormone (SH) , which control the production of hormones in other glands: thyroid, adrenals, & gonads. </li></ul>
  20. 22. <ul><li>GROWTH HORMONE controls the growth of the body during childhood, until adolescence. </li></ul><ul><li>Too little of the growth hormone is childhood leads to dwarfism. </li></ul><ul><li>Too much causes gigantism. </li></ul><ul><li>Later on in life (adulthood), when the length of bones is fixed, too much of growth hormone causes thickening of the limbs and jaws, giving the person a distorted appearance. </li></ul>
  21. 23. <ul><li>PROLACTIN has the effect of enlarging the breasts so that milk production occurs during pregnancy. </li></ul><ul><li>THYROID STIMULATING HORMONE (TSH) promotes the secretion of the thyroid gland. </li></ul><ul><li>ADRENOCORTICOTROPIC HORMONE (ACH) promotes the secretion of corticosterone by the adrenals. </li></ul><ul><li>GONADOTROPINS include FOLLICLE STIMULATING HORMONE (FSH) and LUTEINIZING HORMONE (LH) , both of them stimulate the gonads (ovaries or testis) to produce ova or eggs/sperms. </li></ul>
  22. 24. <ul><li>The production and release of these 4 hormones is partially controlled through a negative feedback system. </li></ul><ul><li>The presence in the blood of the hormone produced by the target gland (thyroid/adrenals/gonads) will control the release of the Stimulating Hormone from the pituitary. </li></ul><ul><li>This feedback also works on the hypothalamus and in this way also, ( indirectly ) on the pituitary, by altering the secretion of hypothalamic releasing hormones . </li></ul>
  23. 25. Hormones Secreted by the Pituitary Gland
  24. 26. THYROID GLAND <ul><li>Butterfly shaped gland located at the base of the neck just below the larynx. </li></ul><ul><li>It is composed of 2 lobes, jointed together by a horizontal bridge. </li></ul><ul><li>In adults it weighs approximately 20 g. </li></ul><ul><li>The gland secretes thyroxine . </li></ul><ul><li>Thyroxine controls the metabolic rate, i.e. the speed at which cells consume and process food an oxygen. </li></ul><ul><li>Another secretion is calcitonin, which helps deposition of calcium in the bones. </li></ul>
  25. 27. THYROXINE <ul><li>… increases the amount of energy used by the cell and increases heat production. </li></ul><ul><li>… stimulates bone growth. </li></ul><ul><li>… is essential for normal brain development. It is also necessary for the brain to function normally in adulthood. </li></ul><ul><li>Iodine is essential for thyroxine formation. </li></ul><ul><li>A lack of iodine in the diet will result in thyroid malfunction. </li></ul><ul><li>Iodine is present in sea food, sea water, salt, & is deficient in the soil in hilly areas. </li></ul>
  26. 28. WHAT HAPPENS WHEN THYROXINE IS DEFICIENT <ul><li>BEFORE BIRTH </li></ul><ul><li>Physical growth is retarded </li></ul><ul><li>Mental retardation </li></ul><ul><li>They are called cretins and the condition is called cretinism . </li></ul><ul><li>AFTER BIRTH </li></ul><ul><li>Metabolic rate is decreased. </li></ul><ul><li>Person gains weight. </li></ul><ul><li>Body temperature decreases. </li></ul>
  27. 29. <ul><li>Mental processes and reflexes slow down – an example of a reflex is that if we reach out for something which is burning hot then we withdraw our hand hurriedly. </li></ul><ul><li>In case of thyroid deficiency the speed with which we withdraw our hand, slows down. </li></ul>
  28. 30. <ul><li>IF A PERSON WITH THYROID DEFICIENCY IS EXAMINED – WE FIND </li></ul><ul><li>Lower metabolic rate. </li></ul><ul><li>Lower temperature </li></ul><ul><li>Gain in body weight, and a puffy appearance. This swelling does not ‘pit’ on pressure. </li></ul><ul><li>Mental processes slowed down </li></ul><ul><li>Heart rate decreases. </li></ul>
  29. 31. <ul><li>WHAT HAPPENS WHEN THYROXINE IS SECRETED IN INCREASED AMOUNTS </li></ul><ul><li>Metabolic rate increases </li></ul><ul><li>Body temperature is raised. </li></ul><ul><li>Body weight is reduced. </li></ul><ul><li>Mental processes are speeded up. The reflex responses are also quicker than normal. Some persons are anxious and irritable. </li></ul><ul><li>Heart rate increases </li></ul>
  30. 33. Decreased levels of thyroxin causes a decrease in the cellular respiration rate.  cells produce less energy and become less active.
  31. 34. PARATHYROID GLANDS <ul><li>There are 4 parathyroid glands. </li></ul><ul><li>These glands are very small. </li></ul><ul><li>They are present on the back surface of the thyroid gland. </li></ul><ul><li>Parathormone , which is secreted by the parathyroids regulates the level of calcium in the blood. </li></ul><ul><li>Hence it functions along with calcitonin which is secreted by the thyroid gland. </li></ul><ul><li>In case too much of parathormone is secreted, calcium is removed from the bones. </li></ul>
  32. 35. PARATHYROID GLANDS <ul><li>Attached to or embedded in the back surface of the thyroid gland, two in each lobe. </li></ul><ul><li>Produces parathyroid hormone ( PTH ) regulates the calcium levels in the blood by increasing the reabsorption of calcium in the kidneys and by increasing the uptake of calcium from the digestive system. </li></ul>
  33. 36. ADRENAL GLANDS (CORTEX & MEDULLA) 1. One gland is located on top of each kidney. 2. Composed of two very different types of tissue a. Outer - The adrenal cortex     b. Inner - The adrenal medulla
  34. 37. ADRENAL GLANDS <ul><li>The adrenal (suprarenal) glands are a pair of glands placed on top of each kidney, rather like a cap. </li></ul><ul><li>Each gland is composed of two distinct parts: the central adrenal medulla and the surrounding adrenal cortex. </li></ul><ul><li>The two parts have separate functions, which influence one another. </li></ul>
  35. 38. ADRENAL MEDULLA <ul><li>The adrenal medulla produces the hormones adrenalin and noradrenalin . </li></ul><ul><li>These are known as the ‘fight or flight’ hormones. </li></ul><ul><li>The release of these hormones is controlled by the sympathetic nervous system. </li></ul><ul><li>Their effects are similar to those of sympathetic nerve stimulation. </li></ul>
  36. 39. ADRENAL CORTEX <ul><li>Produces several hormones called steroids . </li></ul><ul><li>These hormones are released as soon as stress is encountered. </li></ul><ul><li>It is not actually known why these hormones are essential for the stress response. </li></ul><ul><li>One belief is that they facilitate the action of adrenalin and noradrenalin. </li></ul>
  37. 40. <ul><li>These hormones have various functions: </li></ul><ul><li>Increase the blood sugar levels. </li></ul><ul><li>Control the use of salt in the body. </li></ul><ul><li>Distribution of fat. </li></ul><ul><li>Reduce sensitivity (allergic) reactions. </li></ul><ul><li>Antiinflammatory action. [inflammation = a reaction of the body to injury, irritation, & infection] </li></ul><ul><li>The hypothalamus triggers the secretion of the pituitary SH for the adrenal cortex, in respond to: pain, injury, & emotions. </li></ul>
  38. 41. <ul><li>These steroids have therapeutic use because of their antiinflammatory and antiallergic actions. </li></ul><ul><li>They are used for various diseases, such as arthritis, asthma, and certain skin diseases. </li></ul><ul><li>It is essential to know that steroids have serious side effects on prolonged use. </li></ul>
  39. 42. <ul><li>SIDE EFFECTS </li></ul><ul><li>Diabetogenic : Due to their effect of increasing blood sugar levels, prolonged usage can lead to diabetes. </li></ul><ul><li>Hypertension : Due to salt and water retention, the blood pressure rises. </li></ul><ul><li>Protein breakdown : Leads to thinning of skin, with bruises and striae . </li></ul><ul><li>Redistribution of fat : Leads to characteristic appearance called buffalo hump and moon face . </li></ul>
  40. 43. <ul><li>Osteoporosis : Since excess of steroids causes softening and demineralization of the bones. </li></ul><ul><li>Poor wound healing and increased susceptibility to infections. </li></ul><ul><li>Increase in facial hair and acne. </li></ul>
  41. 44. GONADS <ul><li>Are the reproductive glands – the testes in males, and ovaries in female. </li></ul><ul><li>The 3 main hormones produced by the gonads are testosterone, estrogen, and progesterone. </li></ul><ul><li>Both men and woman have all 3 hormones. </li></ul><ul><li>In men testosterone is predominant, whereas in women estrogen and progesterone are mainly produced. </li></ul>
  42. 45. <ul><li>Testosterone is concerned with development of the secondary sexual characteristics in males (facial hair, deepening of the voice). </li></ul><ul><li>Estrogen has the same function (development of secondary sexual characteristics) in females. </li></ul><ul><li>Both estrogen and progesterone play a role in menstruation and pregnancy. </li></ul>
  43. 46. <ul><li>Estrogens are required for the development of ova and for the formation of the physical characteristics (secondary sex characteristics). </li></ul><ul><li>These characteristics include the development of the female reproductive system, the menstrual cycle begins, widening of the hips, and development of the breast. Puberty. </li></ul><ul><li>Progesterone prepares the uterus for the arrival of a developing embryo - or controls the menstrual cycle. </li></ul>
  44. 47. <ul><li>Male gonads or testes produce sperm, and sex hormones that affect cells throughout the body. Testes produce Androgens or the male sex hormone. It regulates male secondary sex characteristics. </li></ul><ul><li>Androgens: the development of physical (secondary sex) characteristics associated. Puberty. These characteristics include the growth of facial hair, increase in body size, and deepening of the voice. </li></ul>
  45. 48. PANCREAS <ul><li>Located in the abdominal cavity. </li></ul><ul><li>It is not primarily an endocrine gland, the main function being to produce digestive juices . </li></ul><ul><li>The hormone producing portion of the pancreas consists of clusters of cells that resemble islands, called islets of langerhans , function as an endocrine gland. </li></ul><ul><li>Each islet is composed of beta cells which secretes insulin , and alpha cells which secretes glucagon , both concerned with control of blood sugar levels. </li></ul>
  46. 49. <ul><li>These two hormones, insulin and glucagon regulate the metabolism of blood glucose (sugar) and the hormones have opposite effects. ( Antagonistic hormones ) </li></ul><ul><li>Insulin stimulates its target cells to take up and use glucose. This action lowers blood glucose levels.  &quot; Use or store &quot; </li></ul>
  47. 50. INSULIN <ul><li>A very important hormone. </li></ul><ul><li>It reduces the blood sugar level. </li></ul><ul><li>It does this by causing sugar to enter the cells, and helping the cells to ‘burn’ the sugar in the blood, and convert it into energy. </li></ul><ul><li>Insufficiency of insulin results in Diabetes Mellitus in which the blood sugar level is raised . </li></ul><ul><li>An increase in blood sugar level is strong stimulus for insulin secretion. </li></ul>
  48. 51. GLUCAGON <ul><li>Raises blood sugar levels by increasing the breakdown of sugar stores in the liver. </li></ul><ul><li>Exercise, infections, and other stresses stimulate the secretion of glucose. </li></ul>
  49. 52. PINEAL GLAND <ul><li>Is a tiny gland (approx. 5-8 mm by 3-5 mm) </li></ul><ul><li>This gland begins to stop functioning before puberty. </li></ul><ul><li>It secretes melatonin , which is secreted in greater amounts in the dark. </li></ul><ul><li>Melatonin is believed to inhibit gonadal development. </li></ul><ul><li>The function of the pineal gland is still being investigated. </li></ul>
  50. 53. THE PINEAL GLAND Located near the base of the brain . Secretes Melatonin . Melatonin increases at night and decreases in the day. This cyclic release helps regulate sleep.
  51. 55. THYMUS <ul><li>The thymus gland is located beneath the sternum ( breastbone ) and between the lungs. </li></ul><ul><li>The thymus produces cells ( lymphocytes / T-cells ) which play a role in the body’s defense. </li></ul><ul><li>Secretes Thymosin , an amino acid based hormone that stimulates the formation of t-cells, which help defend the from pathogens. </li></ul><ul><li>Like the pineal gland, the thymus also starts to decrease in size around adolescence. </li></ul>
  52. 56. PROSTAGLANDINS 1. PROSTAGLANDINS are a group of hormone-like lipids, that also regulate cell activities. 2. Unlike hormones, prostaglandins are NOT produced by specific endocrine glands. 3. They are produced in small quantities by many cells throughout the body.  They act locally .
  53. 57. 4. Relaxation of Smooth Muscles that line the air passages and blood vessels, regulation of blood pressure, contraction of the intestinal walls and the uterus, and stimulation of the body's inflammatory response to infection.
  54. 58. DIGESTIVE ORGANS <ul><li>Endocrine cells within the walls of some digestive organs also secrete a variety of hormones that help digest food. </li></ul><ul><li>When food is eaten, endocrine cells in the stomach lining secrete gastrin , a hormone that stimulates other stomach cells to release digestive enzymes and hydrochloric acid (HCL). </li></ul><ul><li>Endocrine cells of the small intestine release secretin , a hormone that stimulates the release of various digestive fluids from the pancreas and bile from the liver. </li></ul>
  55. 59. DIABETES MELLITUS TYPE I OR JUVENILE ONSET Before age 25, little or no insulin production, requires a strict diet and daily injections of insulin. TYPE II OR ADULT ONSET After age 40, produce normal amounts of insulin, but cells are unable to respond properly because of lack of insulin receptors, can be controlled by diet.
  56. 60. 11. HYPOGLYCEMIA CAUSED BY EXCESS (HIGH) INSULIN OR LOW BLOOD SUGAR, A Disorder in which Glucose is Stored rather than being properly delivered to the cells of the body – causing cells to starve to death. This leads to a lower blood glucose concentration and subsequent release of Glucagon and Epinephrine ( Adrenaline ).
  57. 61. Symptoms of hypoglycemia include Lethargy, Dizziness, Nervousness, Overactivity, and in extreme cases, Unconsciousness ( Ketoacidosis or Diabetic Coma ) and DEATH. 12. HYPERGLYCEMIA CAUSED BY LOW INSULIN OR HIGH BLOOD SUGAR. Can cause Nausea and Rapid Breathing, possibly leading to Oxygen Deficiency, Circulatory and Nervous System Failure, Diabetic Coma, or even Death.
  58. 62. STRESS & HEALTH A. Factors that serve as stressors to the body produce stress and threaten homeostasis. B. Types of Stress Stress may be physical, psychological, or some combination of the two. 1. Physical stress threatens the survival of tissues, such as extreme cold, prolonged exercise, or infections.
  59. 63. <ul><li>2. Psychological stress results from real or perceived dangers, and includes feelings of anger, depression, fear, and grief; sometimes pleasant stimuli cause stress. </li></ul><ul><li>C. Response to Stress </li></ul><ul><li>Responses to stress are designed to maintain homeostasis. </li></ul><ul><li>The hypothalamus controls the general stress syndrome, which involves increased sympathetic activity and increased secretion of cortisol, glucagon, growth hormone, and antidiuretic hormone. </li></ul>
  60. 64. FEEDBACK MECHANISMS The endocrine system uses feedback mechanisms to respond and adjust to changes that occur in and outside the body.  In a Feedback Mechanism , the last step in a series of events controls the first step.
  61. 65. HOMEOSTASIS 1. HOMEOSTASIS is defined as a STABLE internal environment. 2. ANTAGONISTIC HORMONES have opposite effect on the body. 3. To maintain homeostasis, hormone secretions must be tightly regulated. 4. Most hormones are controlled by a FEEDBACK MECHANISM .
  62. 66. 5. NEGATIVE FEEDBACK INHIBITS further release of the initial hormone. 6. POSITIVE FEEDBACK STIMULATES further release of the initial hormone. Glycogen secretion Insulin secretion Blood glucose level decreases Blood glucose level Increases
  63. 67. NEGATIVE FEEDBACK MECHANISMS Regulating Hormone Release 1. Regulates the release of 30 Hormones . 2. Involves interactions of nervous, endocrine, and circulatory systems. 3. Involves hypothalamus and anterior pituitary
  64. 68. A Good Example is a Thermostat, AC, etc.
  65. 69. See previous chart: Hormones Secreted by the Pituitary Gland Summary of Endocrine Glands and their Functions
  66. 70. THANK YOU