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Animal Science 434 Reproductive Physiology

Delve into the intricate world of endocrinology and learn about the functions of the endocrine system, hormonal manipulation, gland classification, hormone properties, and the role of hypothalamus and pituitary in regulating body functions.

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Animal Science 434 Reproductive Physiology

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  1. Animal Science 434Reproductive Physiology Lecture 6 and 7: Endocrinology

  2. What is the function of the endocrine system?

  3. Integration of Body Functions • nervous and endocrine system are similar • nervous system • seconds • endocrine system • minutes and hours

  4. Neuro-endocrine Response

  5. Manipulation of the Endocrine System • Hormones can be used to regulate body functions • growth (anabolic steroids) • lactation (GH or STH) • birth control (Estradiol, Progesterone) • estrous cycle (PGF2) • superovulation and embryo transplant (FSH,eCG) • parturition (oxytocin)

  6. Endocrine Gland • A ductless gland • Secretes substances (hormones) into blood or lymph that affect cells elsewhere in the body • The secretion does not involve loss of tissue

  7. Exocrine Gland • A gland with ducts that are used for secretion

  8. Hormone • Substance produced by endocrine gland • Acts on cells, tissues or organs at a place other than where produced • Acts as a catalyst.

  9. Endocrine Glands Hypothalamus Ovary Adrenal Pineal Uterus Pituitary Placenta Testes (in bull) Thyroid Pancreas

  10. Classification and Properties of Hormone A. Site of Production B. Type of action 1. Primary hormone of reproduction 2. Metabolic hormone C. Chemical Structure 1. General structure • Proteins and polypeptides • Steroids • Fatty acids • Modified amino acid 2. Size

  11. Classification and Properties of Hormone A. Site of Production B. Type of action 1. Primary hormone of reproduction 2. Metabolic hormone C. Chemical Structure 1. General structure • Proteins and polypeptides • Steroids • Fatty acids • Modified amino acid 2. Size

  12. Location of the Hypothalamus and Pituitary Gland

  13. Hypothalamus

  14. Function of Hypothalamus • appetite • thirst • body temperature • vasomotor activity • emotion • use of body nutrient reserves • activity of intestine • sleep • sexual behavior • Production and release of releasing hormones

  15. Releasing Hormones of the Hypothalamus A. Structure • short chain polypeptides (3 - 44 amino acids) B. General Function • to cause the release of trophic hormones from the anterior pituitary gland

  16. Releasing Hormones of the Hypothalamus C.Hormones • Gonadotropin releasing hormone (GnRH) • LH, FSH release • Thyrotrophin releasing hormone (TRH) • TSHand prolactin release • Corticotrophin releasing hormone (CRH) • ACTH release • Growth hormone releasing hormone (GH-RH) • Somatostatin (growth hormone inhibiting hormone)

  17. Hypothalamus

  18. Hypothalamus Cells of the Anterior Pituitary Preoptic nuclei cell Nerve Cells Superior hypophyseal artery Capillary plexus Hypophyseal portal vessels Posterior pituitary • LH • FSH • Prolactin • STH • TSH • ACTH Capillary plexus

  19. Anterior Pituitary Hormones A. Structure 1. glycoproteins or proteins B. Hormones 1. gonadotropins • Follicle stimulating hormone (FSH) • Luteinizing hormone (LH) • Prolactin

  20. Anterior Pituitary Hormones 2.Other trophic hormones • Adrenal Corticotropin (ACTH) • thyroid stimulating hormone (TSH) • growth hormone (GH or STH)

  21. Structure of LH, FSH and TSH • Made of 2 amino acid chains • a chains are the same • b chains differ and give specificity a S S b

  22. Hypothalamus Anterior Pituitary Supraoptic nuclei cell Paraventricular nuclei cell Nerve Cells Capillary plexus Posterior pituitary • Oxytocin • ADH

  23. Hypothalamus Nuclei that produce posterior pituitary hormones

  24. Posterior Pituitary Hormones A.Structure • polypeptides (9 amino acids) B. Hormone • Oxytocin - contraction of smooth muscle

  25. Placental Hormones A.Equine Chorionic Gonadotropin (eCG) 1. FSH-like activity (some LH) 2. long half-life 3. In blood and not urine 4. Function • stimulates follicular growth during pregnancy • LH-like activity stimulates follicles to form accessory CLs

  26. Placental Hormones (cont.) • Other commercial hormones from the equine placenta • Estrogens (several) • Found in mare urine • Premarin is commercial name • Treatment of postmenopausal women • Estrogen replacement therapy • Prevents osteoporosis • Reduces heart disease

  27. Placental Hormones (cont.) B. Human Chorionic Gonadotropin (HCG) 1. LH-like activity. 2. In blood and urine. 3. Function • prevents CL regression C. Placental Lactogen (PL) • Has both GH- and prolactin-like activity. • Development of mammary gland

  28. Gonadal Polypeptide Hormones A. Relaxin • Secreted by CL during pregnancy. • Prior estrogen exposure required • Functions • cervical dilation • inhibits uterine contractions

  29. Gonadal Polypeptide Hormones B. Inhibin • Male - Sertoli cells • Female - granulosa cells • Function • inhibits FSH secretion without altering LH secretion

  30. Gonadal Steroids A. General 1. Origin - ovary, testis, adrenal 2. Structure

  31. SteroidSynthesis Cholesterol Pregnenolone 27-C 21-C OH Estradiol 18-C HO 19-C 21-C Progesterone Testosterone

  32. Gonadal Steroids Cont. B.Androgens 1. Testosterone. • Source • Male - Leydig cells • Female - theca interna • Adrenal • Bound in blood

  33. Gonadal Steroids cont. • Function in the male • spermatogenesis • epididymis • accessory sex glands and secondary sex organs • male secondary sex characteristics • anabolic activity • inhibits GnRH and LH release

  34. Gonadal Steroids Cont. C. Estrogens • Estradiol. • Female - granulosa cells, placenta, adrenal • Male - Sertoli cells, adrenal • Transported in blood by steroid binding globulin

  35. Gonadal Steroids Cont. 4.Functions • CNS • Uterus growth • Uterus contraction • female secondary sex characteristics • mammary gland • stimulates or inhibits GnRH and LH release • nonreproductive a. calcium uptake and bone ossification b. anabolic and growth effects

  36. Gonadal Steroids Cont. D. Progestins 1. An example is progesterone 2. Produced in the CL, the placenta and the adrenal gland. 3. Transported in the blood bound to steroid binding globulin. 4. Functions • prepares the uterus for implantation and pregnancy • acts with estrogen to induce the behavior patterns of estrus • develops alveoli of mammary gland • inhibits the rise of LH that causes ovulation by inhibiting GnRH and LH release

  37. SteroidSynthesis Cholesterol Pregnenolone Mitochondria OH Estradiol Smooth ER HO Progesterone Testosterone

  38. Other Hormones A. Prostaglandins 1. An example is PGF2a

  39. Aspirin inhibits Lipid Hormones - Prostaglandins Fatty Acids Prostaglandins 1. Produced by all tissues of body 2. Can have a local effect on tissues (same tissue which produced it) 3. Rapidly degraded in lungs Phospholipids - Rate limiting (Phospholipase A2) - Precursor to Prostaglandins Arachidonic Acid Cyclo-oxygenase • Vasoconstriction • CL regression • Ovulation • Parturition • Sperm transport • Vasodilation • Maintain CL • Ovulation • Implantation PGF2a PGE2

  40. Other Hormones B. Melatonin 1. Secreted from the pineal gland. 2. Is a modified amino acid 3. Functions to integrate effects of light on reproductive processes.

  41. Other Hormones C. Human Menopausal Gonadotropin (hMG) • Anterior pituitary gland • menopause. • FSH-like activity • long half-life. • no estradiol feedback. • In urine • Perganol

  42. Classification and Properties of Hormone A. Site of Production B. Type of action 1. Primary hormone of reproduction (FSH, LH, estradiol, progesterone) 2. Metabolic hormone (thyroxin, insulin, STH)

  43. Classification and Properties of Hormone • Chemical Structure • Polypeptides - hypothalamic • Protein - pituitary, gonad • Steroids - gonad, adrenal • Fatty acid - many sources, prostaglandins • Modified amino acid - pineal

  44. Chemical Structure of Hormones polypeptide modified amino acid proteinsex steroid fatty acid GnRh melatonin LH Estradiol PGF TRH FSH Progesterone CRH Prolactin Testosterone GHRH ACTH Somatistatin TSH Oxytocin GH or STH Relaxin Inhibin 2

  45. Chemical Structure of Hormones Molecular size of hormones that regulate reproduction Hormone Molecular Weight FSH 30,000 to 37,000 LH 26,000 to 32,000 Prolactin 23,000 to 25,000 HCG 37,700 eCG 28,000 Relaxin 6,500 ACTH 4,500 Inhibin >10,000 Oxytocin 1,007 GnRH 1,200 Estradiol 300 Testosterone 300 Progesterone 300 PGF 300 2

  46. Chemical Structure of Hormones Cont. Polypeptide and protein hormones are made of peptide bonds These hormones can not be given orally!

  47. Chemical Structure of Hormones Cont. Steroids PROGESTERONE CORTISOL These hormones can be given orally!

  48. Mechanism of Hormone Action

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