Endocrine Physiology andMechanisms of Hypothalamic-    Pituitary Regulation         Chapter 39
Endocrine System • Composed of cells and organs that are specialized to   synthesize and secrete hormones into the   blood...
How to go through the Endocrine                 System?•   What is the gland?•   What triggers it to secrete?•   What is t...
THEN…..• Three things that make a gland secrete:1. Hormonal stimulation   – Hormone to hormone      • Hypothalamus  pitui...
Endocrine vs. Exocrine Glands  Where do they secrete their products?
Endocrine System
HORMONAL CONTROLWhat is negative feedback?• Occurs when there is a  drop in the level of a  hormone – triggers a chain rea...
Where is the hormone going?• Only the target cells for a given hormone  have receptors that bind and recognize that  hormo...
Endocrine Glands
Endocrine GlandsEndocrine Glands
Hormones• Neurocrine—secretion of  hormones into the bloodstream  by neurons• Endocrine—secretion of  hormones into the bl...
Hormones • Water soluble   – Peptides   – Tyrosine-derived catecholamines:      • Epinephrine, Norepinephrine, Dopamine • ...
Hormones: Tyrosine-derived catecholamines
Hormones: Tyrosine-derived thyroid hormones
Hormones:   steroids
Hormones: Mechanism of action  Hormones with Cell Membrane Receptors  • Water-soluble hormones have a hormone-binding site...
Hormones: Mechanism of action      Hormones with Cell Membrane Receptors               Water Soluble Hormones
Hormones: Mechanism of action     Hormones with Cell Membrane Receptors
Hormones: Mechanism of action  Hormones with Intracellular Receptors  • Lipid-soluble (thyroid and steroid) hormones diffu...
Lipid-Soluble Hormones
Hormones: Regulation    Hormone Synthesis, Secretion, Metabolism    • Most endocrine hormones are polypeptides      manufa...
Hormones: Regulation    Hormone Synthesis, Secretion, Metabolism    • Water-soluble hormones       – Peptide hormones: CON...
Hormones: Regulation    Hormone Synthesis, Secretion, Metabolism    • Lipid-soluble hormones       – Steroid hormones: FOR...
Pituitary Gland
Pituitary Gland
Pituitary Gland  Pituitary Gland (Hypophysis)  • Located beneath the    hypothalamus in the sella    turcica  • Connected ...
HORMONES OF THE PITUITARY        GLAND• Divided into two lobes – anterior pituitary lobe is larger and   produces SIX horm...
Sphenoid bone                      Portal veins deliver releasing & inhibiting hormones from hypothalamus.    Pituitary Gl...
Flow of                                               Blood to                                               Anterior     ...
Hypothalamic Neurosecretory Cells•Does not synthesize hormones• Hormones packaged & travel by axons of hypothalamic neurons
Anterior vs. Posterior Lobes•Growth Hormone         Oxytocin(hGH)                   Antidiuretic hormone•Thyroid Stimulati...
Anterior PituitaryGland Hormones
Pituitary Gland  • The hypothalamus regulates endocrine function of the    ANTERIOR PITUITARY by SECRETING RELEASING AND  ...
Pituitary Gland
Endocrine GlandsPosterior Pituitary   Gland
Posterior Pituitary Gland Target: V2 receptors of distal renal tubule          cells   Aquaporins move  from cytoplasm to ...
What is diabetes insipidus?           -DECREASED ADH           -Excretion of large amounts of           dilute urine      ...
Endocrine GlandsAnterior Pituitary   Gland                             Hypothalamic neurons
Anterior Pituitary GlandHypothalamichormones bind toreceptors onpituitary cells
Thyroid Gland
On each side of trachea is lobe of thyroid                Butterfly-shaped gland; located in the anteriorThyroid Gland   p...
Thyroid Gland • Main function of thyroid is production and secretion of   metabolically active hormones that are essential...
THYROID– Secretes 3 hormones: • Thyroxine/ Tetraiodothyronine (T4) • Triiodthyronine (T3) • Calcitonin: Decreases the leve...
Thyroid Gland  Most important thyroid hormones are:   - Thyroxin (T4)   - Triiodothyronine (T3)   → Approximately 90% of t...
Thyroid•Follicle = sac of stored hormone                            Makes thyroglobulinContains thyroglobulinwith attached...
Actions of Hormones from      Thyroid Gland •  T3 & T4 : thyroid hormones   responsible for our metabolic   rate, synthesi...
Thyroid GlandTrap dietary iodine   TSH stimulationSynthesizethyroglobulin +thyroid peroxidase
Control of T3 & T4         Secretion• Negative feedback system• Low blood levels of  hormones stimulate  hypothalamus• It ...
Parathyroid•   4 pea-sized glands found on back of thyroid gland
PARATHYROID GLANDS• PTH: increases serum calcium and decreases  serum phosphate• PTH=Phosphate Trashing Hormone     • 1. I...
Parathyroidhormone (PTH)       &Calcitonin (CT)
Adrenal Gland
ADRENAL GLANDS• Two adrenal glands located on top of each  kidney; each has two parts  – Cortex    • Mineralocorticoids   ...
Adrenal Gland
Adrenal Glands
Adrenal Gland
Lowbloodflow
Adrenal Gland:   Aldosterone
Glucocorticoid: Cortisol• Glucose formation: gluconeogenesis (prime effect)• Breakdown of protein    • (increase release o...
Adrenal Gland:   Cortisol                        Normally cortisol is present in the                        body at higher...
Adrenal Gland:   Cortisol
Categories of Endocrine Disease• Hyposecretion• Hypersecretion• Target cell hyporesponsiveness
Categories of Endocrine Disease• Hyposecretion  – Primary hyposecretion occurs when an    ENDOCRINE GLAND releases an inad...
Categories of Endocrine Disease (Cont.)• Hypersecretion  – Primary hypersecretion occurs when there is a    DYSFUNCTION OF...
Categories of Endocrine Disease• Target cell hyporesponsiveness  – Typically due to lack of or a deficiency in cellular   ...
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  1. 1. Endocrine Physiology andMechanisms of Hypothalamic- Pituitary Regulation Chapter 39
  2. 2. Endocrine System • Composed of cells and organs that are specialized to synthesize and secrete hormones into the bloodstream to act at distant target cells • Hormones are blood-borne chemical messengers that affect target cells anatomically distant from the secreting cell
  3. 3. How to go through the Endocrine System?• What is the gland?• What triggers it to secrete?• What is the secreted product (hormone)?• What is the target of the hormone?• What is the resulting work of the hormone?
  4. 4. THEN…..• Three things that make a gland secrete:1. Hormonal stimulation – Hormone to hormone • Hypothalamus  pituitary • Pituitary  thymus2. Humoral fluids – What ions/proteins in the fluids • Ca2+ levels, blood sugar3. The Nervous System – Sympathetic stimuli • Epinephrine and norepinephrine
  5. 5. Endocrine vs. Exocrine Glands Where do they secrete their products?
  6. 6. Endocrine System
  7. 7. HORMONAL CONTROLWhat is negative feedback?• Occurs when there is a drop in the level of a hormone – triggers a chain reaction of responses to increase hormones in the blood – most hormones are regulated by negative feedback – OXYTOCIN: POSITIVE FEEDBACK
  8. 8. Where is the hormone going?• Only the target cells for a given hormone have receptors that bind and recognize that hormone.
  9. 9. Endocrine Glands
  10. 10. Endocrine GlandsEndocrine Glands
  11. 11. Hormones• Neurocrine—secretion of hormones into the bloodstream by neurons• Endocrine—secretion of hormones into the bloodstream by endocrine glands• Paracrine—hormone molecule secreted by one cell affects adjacent cells• Autocrine—hormone molecule secreted by a cell affects the secreting cell
  12. 12. Hormones • Water soluble – Peptides – Tyrosine-derived catecholamines: • Epinephrine, Norepinephrine, Dopamine • Lipid soluble – Tyrosine-derived Thyroid hormones: • T3, T4 – Steroids
  13. 13. Hormones: Tyrosine-derived catecholamines
  14. 14. Hormones: Tyrosine-derived thyroid hormones
  15. 15. Hormones: steroids
  16. 16. Hormones: Mechanism of action Hormones with Cell Membrane Receptors • Water-soluble hormones have a hormone-binding site located on the external portion of a specific cell-surface receptor • Hormones exert their action by binding to target cell receptor proteins • Once binding takes place, a conformation of the receptor protein conveys a signal to the interior of the cell • Amplification of the hormone activity is achieved by activation of a cascade of chemical reactions
  17. 17. Hormones: Mechanism of action Hormones with Cell Membrane Receptors Water Soluble Hormones
  18. 18. Hormones: Mechanism of action Hormones with Cell Membrane Receptors
  19. 19. Hormones: Mechanism of action Hormones with Intracellular Receptors • Lipid-soluble (thyroid and steroid) hormones diffuse easily through the lipid bilayer of cell membranes • Receptors for these hormones are located in the cytoplasm, or in the nucleus of the target cell • Binding causes a change in affinity of the receptor for binding sites on DNA in the cell nucleus • Gene expression is changed by binding of the hormone-receptor complex to specific DNA binding sites • Onset of action of lipid-soluble hormones is slow compared with water-soluble hormones and there is no amplification cascade
  20. 20. Lipid-Soluble Hormones
  21. 21. Hormones: Regulation Hormone Synthesis, Secretion, Metabolism • Most endocrine hormones are polypeptides manufactured on the rough endoplasmic reticulum and stored in vesicles within the cells • Cleaved by specific enzymes to release the active form of the hormone Enzyme Pre hormone Cleavage Hormone fragment
  22. 22. Hormones: Regulation Hormone Synthesis, Secretion, Metabolism • Water-soluble hormones – Peptide hormones: CONTAINED WITHIN LIPID BILAYER OF THE VESICLES and stored until a trigger results in exocytosis of the hormone into the extracellular space – Catecholamines: formed by enzymes within the cytoplasm that begin with tyrosine and through a series of steps convert it to dopamine, norepinephrine, or epinephrine
  23. 23. Hormones: Regulation Hormone Synthesis, Secretion, Metabolism • Lipid-soluble hormones – Steroid hormones: FORMED ON DEMAND from cholesterol that is stored in the cell or retrieved from the circulating lipoproteins – Thyroid hormones: synthesis precedes secretion by weeks or months in the thyroid follicle and bound to protein thyroglobulin; secretion occurs via cleavage of the thyroid hormone based on systemic needs determined by the hypothalamus and pituitary gland
  24. 24. Pituitary Gland
  25. 25. Pituitary Gland
  26. 26. Pituitary Gland Pituitary Gland (Hypophysis) • Located beneath the hypothalamus in the sella turcica • Connected to hypothalamus by the pituitary stalk • • Composed of anterior (adenohypophysis) and posterior (neurohypophysis) lobes
  27. 27. HORMONES OF THE PITUITARY GLAND• Divided into two lobes – anterior pituitary lobe is larger and produces SIX hormones; stimulated by releasing and inhibiting hormones from the hypothalamus; connected by hypophyseal portal veins – posterior pituitary lobe is smaller and consists primarily of axons whose cell bodies are in the hypothalamus
  28. 28. Sphenoid bone Portal veins deliver releasing & inhibiting hormones from hypothalamus. Pituitary Gland
  29. 29. Flow of Blood to Anterior Pituitary• Releasing & inhibiting hormones enter blood (hypothalamus)• Travel through portal veins• Enter anterior pituitary at capillaries• Hormones travel to destination
  30. 30. Hypothalamic Neurosecretory Cells•Does not synthesize hormones• Hormones packaged & travel by axons of hypothalamic neurons
  31. 31. Anterior vs. Posterior Lobes•Growth Hormone Oxytocin(hGH) Antidiuretic hormone•Thyroid Stimulating (ADH)hormone (TSH)•Follicle StimulatingHormone (FSH)•Luteinizing hormone(LH)•Prolactin (PRL)•Adrenocorticotropichormone (ACTH)
  32. 32. Anterior PituitaryGland Hormones
  33. 33. Pituitary Gland • The hypothalamus regulates endocrine function of the ANTERIOR PITUITARY by SECRETING RELEASING AND INHIBITING HORMONES INTO THE PORTAL SYSTEM between the hypothalamus and pituitary that transports capillary blood from the hypothalamus to the capillaries of the anterior lobe • Release of POSTERIOR PITUITARY hormones occurs WHEN ACTION POTENTIALS GENERATED IN THE HYPOTHALAMIC NEURONS TRAVEL DOWN THE AXONS of the pituitary stalk and trigger exocytosis of hormone from the nerve terminals in the posterior pituitary gland
  34. 34. Pituitary Gland
  35. 35. Endocrine GlandsPosterior Pituitary Gland
  36. 36. Posterior Pituitary Gland Target: V2 receptors of distal renal tubule cells Aquaporins move from cytoplasm to apical tubular epithelial cells H20 Water moves from tubular fluid Cell Interstitium
  37. 37. What is diabetes insipidus? -DECREASED ADH -Excretion of large amounts of dilute urine -Destruction of back of pituitary -OR insensitivity of kidneys to hormone
  38. 38. Endocrine GlandsAnterior Pituitary Gland Hypothalamic neurons
  39. 39. Anterior Pituitary GlandHypothalamichormones bind toreceptors onpituitary cells
  40. 40. Thyroid Gland
  41. 41. On each side of trachea is lobe of thyroid Butterfly-shaped gland; located in the anteriorThyroid Gland part of neck
  42. 42. Thyroid Gland • Main function of thyroid is production and secretion of metabolically active hormones that are essential for regulation of various metabolic processes. • Thyroid hormones are made from tyrosine and iodine.
  43. 43. THYROID– Secretes 3 hormones: • Thyroxine/ Tetraiodothyronine (T4) • Triiodthyronine (T3) • Calcitonin: Decreases the level of calcium in the blood & increases uptake of calcium into bone matrix
  44. 44. Thyroid Gland Most important thyroid hormones are: - Thyroxin (T4) - Triiodothyronine (T3) → Approximately 90% of the thyroid hormone is in the form of T4, whereas 10% is T3 Source: Clinical Chemistry. 2010. Kaplan and Pesce. Mosby.
  45. 45. Thyroid•Follicle = sac of stored hormone Makes thyroglobulinContains thyroglobulinwith attached iodinemolecules
  46. 46. Actions of Hormones from Thyroid Gland • T3 & T4 : thyroid hormones responsible for our metabolic rate, synthesis of protein, breakdown of fats, use of glucose for ATP production • Calcitonin: responsible for building of bone & stops reabsorption of bone by osteolasts (lowers blood levels of Calcium)
  47. 47. Thyroid GlandTrap dietary iodine TSH stimulationSynthesizethyroglobulin +thyroid peroxidase
  48. 48. Control of T3 & T4 Secretion• Negative feedback system• Low blood levels of hormones stimulate hypothalamus• It stimulates pituitary to release TSH• TSH stimulates gland to raise blood levels
  49. 49. Parathyroid• 4 pea-sized glands found on back of thyroid gland
  50. 50. PARATHYROID GLANDS• PTH: increases serum calcium and decreases serum phosphate• PTH=Phosphate Trashing Hormone • 1. Increase bone reabsorption of calcium • 2. Increase kidney reabsorption of calcium • 3. Decrease kidney reabsorption of phosphate • 4. Increase Vitamin D production by stimulating kidney (thus, indirect increase in intestinal calcium)
  51. 51. Parathyroidhormone (PTH) &Calcitonin (CT)
  52. 52. Adrenal Gland
  53. 53. ADRENAL GLANDS• Two adrenal glands located on top of each kidney; each has two parts – Cortex • Mineralocorticoids • Glucocorticoids Regulation the three S’s Salt, sugar and sex • Androgens – Medulla • epinephrine • norepinephrine
  54. 54. Adrenal Gland
  55. 55. Adrenal Glands
  56. 56. Adrenal Gland
  57. 57. Lowbloodflow
  58. 58. Adrenal Gland: Aldosterone
  59. 59. Glucocorticoid: Cortisol• Glucose formation: gluconeogenesis (prime effect)• Breakdown of protein • (increase release of amino acids into blood stream)• Breakdown of fat (lipolysis)• Depression of Immune function • (Prescribed for organ transplants)• Anti-Inflammatory effects • (inhibit WBC’s but also retard tissue repair)• Resistance to stress: Provide tissues with a ready supply of ATP
  60. 60. Adrenal Gland: Cortisol Normally cortisol is present in the body at higher levels in the morning, and at its lowest at night.
  61. 61. Adrenal Gland: Cortisol
  62. 62. Categories of Endocrine Disease• Hyposecretion• Hypersecretion• Target cell hyporesponsiveness
  63. 63. Categories of Endocrine Disease• Hyposecretion – Primary hyposecretion occurs when an ENDOCRINE GLAND releases an inadequate amount of hormone to meet physiologic needs – Secondary hyposecretion occurs when secretion of a TROPIC HORMONE is inadequate to cause the target gland to secrete adequate amounts of hormone
  64. 64. Categories of Endocrine Disease (Cont.)• Hypersecretion – Primary hypersecretion occurs when there is a DYSFUNCTION OF THE ENDOCRINE GLAND that results in abnormally high secretion of hormone – Secondary hypersecretion occurs when there is an ELEVATION IN THE TROPIC LEVEL of one hormone that results in an increased plasma concentration of the endocrine gland hormone also
  65. 65. Categories of Endocrine Disease• Target cell hyporesponsiveness – Typically due to lack of or a deficiency in cellular receptors, but can occur with postreceptor mechanisms, such as second-messenger dysfunction that causes decreased cellular response – Hormone resistance of the target tissues will cause the same set of clinical symptoms as hyposecretion

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