k - 5 & k - 6 reproduction hormone (fisiologi)
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Reproductive System
(Hormone Function)Physiology Department
Medical School, University of Sumatera Utara
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Endocrine Control: Three Levels of Integration
Hormones of the hypothalamic-anterior pituitary pathway
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Hypothalamus
Receives indirect sensory inputs from all sensory systemsSends neural outputs to various motor control nucleiSends neural outputs to sympathetic and parasympathetic nervous systemsSends both neural and hormonal outputs to pituitary
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Function of Hypothalamus
Integrates functions that maintain chemical and temperature homeostasis
Functions with the limbic system
Controls the release of hormones from the anterior and posterior pituitary
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Hypothalamus
Synthesizes releasing hormones in cell bodies of neurons
Hormones are transported down the axon and stored in the nerve endings
Hormones are released in pulses
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Hypothalamic Releasing Hormones
Seven releasing hormones are made in the hypothalamus
Thyrotropin-releasing hormone (TRH)
Corticotropin-releasing hormone (CRH)
Gonadotropin-releasing hormone (GnRH)
Growth hormone-releasing hormone (GHRH)
Growth hormone-release inhibiting hormone (GHIH)
Prolactin-releasing factor (PRF)
Prolactin-inhibiting hormone (PIH)
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Hypothalamus Releasing Hormones: Secretion
Is influenced by emotions
Can be influenced by the metabolic state of the individual
Delivered to the anterior pituitary via the hypothalamic-hypophyseal portal system
Delivered to the posterior pituitary via neural system
Usually initiates a three-hormone sequence
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Is also called the Adenohypophysis
Secretes tropic hormones in a pulsatile fashion
Synthesizes various hormones in various specific cell populations
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HYPOTHALAMIC HORMONE
EFFECTS ON THE ANTERIOR PITUITARY
Thyrotropin-releasing hormone (TRH)
Stimulates release of TSH (thyrotropin) and Prolactin
Corticotropin-releasing hormone (CRH)
Stimulates release of ACTH (corticotropin)
Gonadrotropin-releasing hormone (GnRH)
Stimulates release of FSH and LH (gonadotropins)
Growth hormone-releasing hormone (GHRH)
Stimulates release of growth hormone
Growth hormone-inhibiting hormone (GHIH)
Inhibits release of growth hormone
Prolactin-inhibiting hormone (PIH)
Stimulates release of prolactin
Prolactin-inhibiting hormone (PIH)
Inhibits release of prolactin
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Anterior Pituitary Hormones
Growth Hormone (GH, Somatotropin): primary hormone responsible for regulating body growth, and is important in metabolism
Thyroid-stimulating Hormone (TSH): stimulates secretion of thyroid hormone & growth of thyroid gland
Adrenocorticotropic Hormone (ACTH): stimulates cortisol secretion by the adrenal cortex & promotes growth of adrenal cortex
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Anterior Pituitary Hormones
Follicle-stimulating Hormone (FSH):
Females: stimulates growth & development of ovarian follicles, promotes secretion of estrogen by ovaries.
Males: required for sperm production
Luteinizing Hormone (LH):
Females: responsible for ovulation, formation of corpus luteum in the ovary, and regulation of ovarian secretion of female sex hormones.
Males: stimulates cell in the testes to secrete testosterone
Prolactin:
Females: stimulates breast development and milk production.
Males: involved in testicular function
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Neurohypophysis Hormones
Oxytoxin OT (pitocin)Stimulates smooth muscle contraction
Uterus & Mammary glands
RegulationActions
– Uterine stretching & Suckling
Works with estrogen
Inhibited by progesterone
Also made in uterine wall
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Oxytocin
releasepositive feedback
– uterine stimulation (stretch) and suckling stimulate the hypothalamus to release oxytocin from the posterior pituitary
– stimulates uterine contractions (labor) and milk letdown
– increases feedback for more oxytocin release
inhibited by lack of these stimuli
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Oxytocin
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Endocrine Regulation of Reproduction
Hypothalamus releases LHRH (GnRH) into hypothalamo-hypophyseal portal vessels.
Anterior pituitary secretes:LH (luteinizing hormone).
FSH (follicle-stimulating hormone).
Secreted in pulsatile fashion to prevent desensitization and down regulation of receptors.
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Endocrine Regulation
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Female Reproductive System
(Hormone Function)
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Pituitary-Ovarian Axis
Hormonal interactions between the anterior pituitary and the ovaries.
Anterior pituitary secretes FSH and LH.Controlled by GnRH.
FSH secretion is slightly greater than LH during early phase of menstrual cycle.LH secretion greatly exceeds FSH secretion just prior to ovulation.- feedback.
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Female Reproductive Cycle - Hormones
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Hormone Sources & Functions
Gonadotropin-releasing Hormone (GnRH) :
Source: Hypothalamus
Targets & Functions:Females & Males - Anterior Pituitary
– Stimulates the production of Follicle Stimulating Hormone (FSH) & Leutinizing Hormone (LH)
– Regulates the release of FSH & LH by the anterior pituitary gland
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Hormone Sources & Functions
Follicle Stimulating Hormone: Source: Anterior Pituitary
Targets & Functions:Females - Ovaries
– Stimulates follicle growth & maturation
– Stimulates estrogen production
Males - Seminiferous Tubules– Promotes sperm production
(Spermatogenesis) by establishing testosterone receptors on tubules
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Leutenizing Hormone:
Source: Anterior PituitaryTargets & Functions:
Females - Ovaries– Stimulates primary oocyte to complete
first meiotic division to become secondary oocyte
– Triggers ovulation of secondary oocyte– Transforms ruptured follicle into corpus
luteum
– Stimulates production of progesterone by corpus luteum
Males - Seminiferous Tubules– Stimulates sperm production
(Spermatogenesis) by causing interstitial cells in testes to secrete testosterone
Corpus luteum
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Estrogen:Sources: Maturing Follicles & Corpus Luteum
Targets & Functions:Body in general
– Stimulates the development of female secondary sexual characteristics
Breasts– Stimulates development of milk ducts
and sinuses (ampullae)
Uterus– Stimulates proliferative phase of
uterine cycle
Ovaries– Promotes oogenesis
Anterior Pituitary– Stimulates burst-like release of LH
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EstrogensEstrogens
• estradiol, estrone, estriol
• main site of production = ovaries but can also be produced in other tissues such as adipose
• bound to sex steroid binding globulin (SSBG)
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Steroid hormoneMainly oestradiolProliferation of endometriumThickening of vaginal epitheliumStimulate vaginal secretion (acid & very stringy – test for ovulation)Skeletal maintenanceEffects on brain and behaviour
ESTROGEN
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Reproductive Effects of EstrogensReproductive Effects of Estrogens
• growth/maturation of ovarian follicles
• increased motility of fallopian tubes
• endometrium growth
• thinning/alkalinization of cervical mucus
• stimulates uterine muscles
• increased uterine sensitivity to oxytocin
• breast development, fat deposition
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Progesterone:
Source:Corpus Luteum & PlacentaTargets & Functions:
Females - Uterus– Maintains thickened endometrium– Stimulates nutrient release– Quiets myometrium
Corpus luteumFemales - Breasts
– Stimulates development of alveoli for milk production
Females - Anterior Pituitary– Inhibits production & release of FSH &
LH
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Steroid hormoneIncreased appetiteDecreased uterine motility
Thickens cervical mucus
Progestational changes in the endometrium
Progesterone
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Oxytocin:
Sources: Manufactured by hypothalamus. Stored & released by Posterior Pituitary
Targets & Functions:Uterus
– Stimulates contraction of uterine myometrium causing lowering of fetus & labor
Breasts– Stimulates contraction of milk ducts
and sinuses, releasing milk
Positive Feedback Mechanisms:
1. Childbirth - Stretching of uterus and cervix
2. Suckling - Milk letdown reflex
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Prolactin:
Source: Anterior Pituitary
Targets & Functions:Breasts
– Stimulates alveoli of breasts to produce milk
Regulation
– Release of prolactin by anterior pituitary is regulated by hypothalamus production of Prolactin Releasing Hormone (PRH) & Prolactin Inhibiting Hormone (PIH)
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MENSTRUAL CYCLE
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Ovulation
One graafian follicle forms bulge on surface of ovary.
Extrudes secondary oocyte into the uterine tube.
LH causes the empty follicle to become corpus luteum which secretes:
Progesterone and estrogen.If not fertilized, becomes corpus albicans.
Insert fig. 20.33
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Siklus menstruasi
Dibagi atas 3 fase :
- Fase follikular (berlangsung 6 -13 hari)
- Fase ovulatory (hari ke 14)
- Fase luteal (berlangsung 14 hari)
Satu siklus rata-rata 28 hari
Awal siklus dihitung dari hari I haid
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Siklus Mentruasi
FSH mematangkan sel folikel
Pematangan sel folikel mensekresikan estrogen
Kadar estrogen memuncak sebelum hari ke 14→ feedback negatif ke hypothalamus
LH disekresikan
Folikel yang matang pecah →ovulasi Hari ke-14)
Bekas robekan →corpus luteum → progesteron >> dan setrogen <<
Kadar estrogen↑ dan progesteron ↑ → feedback negatif ke hypofise anterior
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Siklus Menstruasi
LH turun secara bermakna
Copus luteum degeneratif → corpus albicans
Progesteron turun kadarnya dalam darah
Menstruasi
Feedback positif
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Prolaktin
Peran: LAKTASI
Diatur oleh GnRH dan TRH
Dihambat oleh dopamin
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Proses Pengeluaran ASI
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Male Reproductive System
(Hormone Function)
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anterior pituitary drives changes during puberty
controlled by GnRH from hypothalamusbegins to secrete FSH, LH
LH – targets interstitial endocrinocytes
testosteronedihydrotestosterone (DHT)
FSH - Sustentacular cellsAndrogen-binding protein (ABP) concentrates androgens for spermatidsInhibin – negative feedback to the pituitary and hypothalamus
Hormones of brain-testicular axis
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Male Reproductive System
Testes:Seminiferous tubules:
Contain receptor proteins for FSH in Sertoli cells.FSH stimulates spermatogenesis to occur.
Leydig cells: LH stimulates secretion of testosterone.Contain receptor proteins for LH.
Insert fig. 20.12
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Control of LH and FSH Secretion
Negative feedback:Testosterone inhibits LH and GnRH production.
Maintain relatively constant secretion of LH and FSH.
– Declines gradually in men over 50 years of age.
– Testosterone converted to DHT, which inhibits LH.
Inhibin inhibits FSH secretion.
Aromatization reaction producing estradiol in the brain, is required for the negative feedback effects.
Insert fig. 20.13
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Onset of Puberty
FSH and LH secretion is high in newborn, but falls to low levels in few weeks.At puberty:
Brain maturation increases GnRH secretion.Decreased sensitivity of gonadotropin to negative feedback.
During late puberty, pulsatile secretion of LH and FSH increase during sleep.
Stimulate a rise in sex steroid secretion.
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Onset of Puberty (continued)
Stimulates rise in testosterone and estradiol-17.
Produce secondary sexual characteristics.
Age of onset related to the % of body fat and physical activity in the female
Leptin secretion from adipocytes may be required for puberty.
Insert fig. 20.10
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Testosterone:Sources: Interstitial Cells in Testes, adrenal korteks from androstenedione
Targets & Functions:Body in general
– Stimulates the development of male secondary sexual characteristics including:
» development of male genitalia» male skeleton and muscle development» male patterns for hair growth» increased RBC production & higher metabolic rate
Seminiferous tubules– Necessary for the completion of
spermatogenesis
Anterior Pituitary– Moderate inhibition of pituitary and hypothalamus
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Developmenttestosterone stimulates pattern development before birth (internal ducts)DHT external genitalsTestosterone converted to estrogens in brain brain development
Puberty – testosterone & DHT stimulate enlargement of male sex organs and secondary sexual characteristics
Hormones of brain-testicular axis
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Testosterone
At puberty testosterone prompts spermatogenesisCauses reproductive organs to grow & assume adult functionsAs adult normal levels of testosterone are required to maintain normal structure & function of reproductive organ
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Sertoli Cells
Form blood-testes barrier:Prevents autoimmune destruction of sperm.Produce FAS ligand which binds to the FAS receptor on surface to T lymphocytes, triggering apoptosis of T lymphocytes.
Prevents immune attack.
Secrete inhibin.Phagocytize residual bodies:
May transmit information molecules from germ cells to Sertoli cells.
Secrete androgen-binding protein (ABP):Binds to testosterone and concentrates testosterone in the tubules.
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Leydig CellsLeydig Cells
• produce/secrete testosterone
• located outside seminiferous tubules
• active in fetus till birth, puberty onward
• some testosterone converted to estradiol
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Estrogen Secretion
Sertoli and Leydig cells secrete small amounts of estradiol.
Receptors found in Sertoli and Leydig cells and accessory organs.
May be responsible for: Negative feedback in brain.Sealing of epiphyseal plates.Regulatory function in fertility.
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Leydig CellsLeydig Cells
• produce/secrete testosterone
• located outside seminiferous tubules
• active in fetus till birth, puberty onward
• some testosterone converted to estradiol
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Hormonal Control of Spermatogenesis
Formation of primary spermatocytes and entry into early prophase I, begin during embryonic development.
Spermatogenesis arrested until puberty.
Testosterone required for completion of meiosis and spermatid maturation.
Secrete paracrine regulators:IGF-1.
Inhibin.
Transforming growth factor.
FSH necessary in the later stages of spermatid maturation.
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