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Lecture 19

AN SC 431W Lecture 19: Lecture 19, 22, 24, 25

3 Pages

Animal Science
Course Code
AN SC 431W
Ott Troy

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ESTROUS CYCLE: THE FOLLICULAR PHASE—KEY CONCEPTS 1. How does the same photoperiod stimulate cyclicity in some species, and inhibit it in others? a. Photoperiod=amount of daylight, light taken in by eye and optic nerve  suprachiasmic nuclei  superior cervical ganglia  pineal gland b. Inhibitory neural signal goes to pineal gland to inhibit melatonin production during day (melatonin produced at night) c. Low melatonin in long photoperiod causes increase RFRP3, acts on the kisspeptin neurons: c.i. Short day breeders=kisspeptin neurons inhibited  low GnRH, FSH and LH  no cyclicity c.ii. Long day breeders=kisspeptin neurons stimulated high GnRH, FSH and LH  cyclicity *opposite would be true for short photoperiod with high melatonin 2. 2-cell, 2-gonadotropin model in follicle wall a. Theca cells: LH binding to receptor activates cholesterol  testosterone b. Granulosa cells: FSH binding to receptor activates testosterone  estrogen, via aromatase enzyme c. When gonadotropin binds to receptor, its activates a second messenger, cyclic AMP (cAMP) c.i. Causes change in cell function by converting hormones to create estrogen 3. Pre-ovulatory LH surge causes ovulation by… a. Expansion of cumulus cells  corona radiata cells explode away  oocyte separates from follicular wall b. Histamine and prostaglandin-E2 production  increased blood flow to ovary and follicle  follicle edema, increased pressure c. Protein synthesis changes in and around follicle  progesterone, plasminogen, prostaglandin-F2alpha synthesized  follicular wall weakens and smooth muscle contracts SPERMATOGENESIS AND MALE ENDOCRINOLOGY 1. Semen extenders are typically isotonic a. Equal concentration of solution and salt, at equilibrium 2. The basis for sorting X and Y bearing sperm is the difference in amount of DNA content 3. Spermatogonia is found in the basal compartment in the seminiferous tubule a. Immature sperm in basal compartment, mature sperm in adluminal compartment 4. During spermatogenesis, developing sperm are primary spermatocytes when they initiate meiosis a. Meiosis makes sperm cells haploid and genetically variable 5. Spermatogenesis occurs in seminiferous tubules of testes 6. Sertoli cells produce estrogen and dihydrotestosterone a. Leydig cells: progesterone  testosterone b. Sertoli cells: testosterone  estrogen (via aromatase) testosterone  dihydrotestosterone (via 5alpha-reductase) 7. Boar and stallion testes produce more estrogen than found in their pregnant female counterparts 8. Sertoli cells in the testes are regulated by FSH a. Called the “nurse ce
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