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Details Title: Fundamentals of Neuroendocrino Description: 4.19.07 Total Flash Cards: 89 Created: 04/23/2007 17:12:50	To study from this set of flash cards, or to create your own your own study flash cards, register HERE. If you are already a registered user, CLICK HERE.
Cards Term What does the nervous system regulate? Definition Nervous system regulates the the endocrine system and the endocrine activity modulates the CNS The hypothalamus and pituitary exert control over the function of several endocrine glands and a wide range of physiologic activities Function is vital for sustaining life and reproductive capacity Term How does communication btw cells occur? Definition Communication between cells occurs via: 1. Gap junctions: direct cell to cell 2. Nerve synapses: secretion of neurotransmitter across a synapse Paracrine: messenger diffuses to local cell 3. Endocrine: hormones secreted into circulation Term How is Neurosecretory endocrine regulation is exemplified? Definition by the neurons in the hypothalamus secreting hormones into the portal system which stimulate the ant pituitary to release hormones Term what are the neuroendocrine messenger? Definition Dopamine; Norepinephrine; Epinephrine; Somatostatin; GnRH; TRH; Oxytocin; Vasopressin; Vasoactive intestinal peptide; Cholecystokinin; Enkephalins; Pro-opiomelanocortin derivatives Term What is the hypothalamus? Definition Hypothalamus - part of the diencephalon at the base of brain above the junction of optic nerves . Composed of a collection of nuclei which control pituitary function Term what is the pituitary gland? Definition The pituitary gland lies at the base of the skull in the sella turcica The pituitary stalk passes through the sellar diaphragm Optic chiasm lies 5-10 mm above the diaphragm Term which neuro nuclei are important for reproduction? Definition PVN, Supraoptic nucleus, arcuate nucleus Term What is the origin of the posterior lobe of the pituitary? Definition The posterior lobe of the pituitary (neurohypophysis) is of neural origin, arising from the ventral hypothalamus and 3rd ventricle Term Where do 100,000 nerve fibers extend from the hypothalamus to? Definition the post pituitary Term Where are the cell bodies of the posterior pituitary? Definition The cell bodies arise primarily in the supraoptic and paraventricular nuclei of the hypothalamus Term What are products of the posterior pituitary? Definition Antidiuretic hormone (ADH) and oxytocin are the only 2 hormones secreted Term What is another name for the anterior pituitary? Definition Also called adenohypophysis Term Is it of neural origin? Definition NOT of neural origin Term Where does it arrise from? Definition Arises from Rathke’s pouch (ectodermal evagination of the oropharynx) and migrates to join the posterior pituitary Term How does neuroregulation occur? Definition Neuroregulation from the hypothalamus occurs via secretion of messengers via the portal circulation Term What is portal circulation? Definition A rich capillary network within median eminence of the hypothalamus drains into the portal vessels into the ant pituitary where Blood flow is bidirectional This system permits rapid communication between the hypothalamus and anterior pituitary Term what is the most vascularized tissue in the body? Definition Anterior pituitary is the most richly vascularized tissue in the body Term What is considered the hypothal? Definition Neurons located in various nuclei secrete releasing and inhibiting hormones targeting the pituitary Term what are the hypothal products? Definition Products include: GNRH, TRH, CRH, Prolactin Inhibiting Substance (DA), GHRH, Somatostatin, ADH, Oxytocin Term are most of the products positive or negative influences? Definition Positive influence over all hormones except prolactin Term How are the numclie in the hypothal regulated? Definition Modulation by hormones in blood and neurotransmitters in brain Term what are nonendocrine functions of the hypothal? Definition Also involved in many non-endocrine functions: ie. thermoregulation, food intake Term what does Somatotrophs do? Definition (growth hormone) Term what do lactotrophs do? Definition Lactotrophs (prolactin) Term what do thyrotrophs do? Definition Thyrotrophs (Thyroid stimulating hormone) Term what do corticotrophs do? Definition qCorticotrophs (adrenocorticotropic hormone) Term what do gonadotrophs do? Definition Gonadotrophs (luteinizing hormone and follicle stimulating hormone) Term which 2 transcription factors control differentiation of primordial pituitary cells? Definition PROP 1, PIT 1 Term what demonstrates panhypopituitarism? Definition Individuals with mutations in genes (for PROP 1 and PIT1) encoding these factors demonstrate panhypopituitarism Term What doe people with panhypopituitarism display? Definition Deficiencies in gonadotropins, TSH, prolactin, and GH Clinical manifestations include stunted growth, hypothyroidism, and delayed puberty in addition to amenorrhea Term What is thhe hypothal? Definition The hypothalamus is the common final pathway by which signals from multiple systems reach the anterior pituitary Hypothalamic function is controlled by hormone mediated signals and neural inputs from a wide variety of sources Steroid and thyroid hormones cross the blood-brain barrier and produce specific receptor-mediated actions Peptides in the general circulation elicit actions indirectly Nerve signals are mediated by neurotransmitters including acetylcholine, dopamine, norepinephrine, Epinephrine, Serotonin, gamma-aminobutyric acid, Opioids Immuno-endocrine interactions also occur: cytokine regulation in response to infection Hypothalamus also sends signals to other areas of brain: cortex, ant pituitary, choroid plexus into CSF Term Where is GnRH synthesize? Definition Cell bodies of neurons synthesizing GNRH located in arcuate nucleus Term How does GnRH get to the Anterior Pituitary? Definition GNRH is carried via axons through the tuberoinfundibular path and secreted into the portal system Term what gene is GnRH encoded on? Definition GNRH is a decapetide encoded by gene on chromosome 8p Term What does GnRH stimulate? Definition Stimulates both FSH and LH secretion from the anterior pituitary Term What does GnRH result in? Definition Maintains basal gonadotropin secretion, phasic release of gonadotropins for folliculogenesis and ovulation, and determines the onset of puberty Term Where do Cells that produce GnRH originate ? Definition from the olfactory area Medial olfactory placode (thickened plate of ectoderm) Term Where do cells that produce GnRH enter the brain? Definition Enter the brain with the nervus terminalis (cranial nerve that projects from the nose to the septal preoptic nuclei) Term What syndrome demonstrates the Olfactory-Hypothalamic Connection: Definition Kallman’s Syndrome Term Why do you get Kallman's syndrome? Definition Deletion of a Xp22.3 Term What does the gene deletion do in KS? Definition Lack of a cell adhesion molecule (KALIG-1) essential for neuronal migration Failure of cells to migrate from olfactory placode to hypothalamus Term what are the manifestations of KS? Definition Isolated GnRH deficiency ; No pubertal development; Impaired sense of smell Term What is GnRH's half life? Definition 1/2 life = 2-4 minutes Term What is critical for nornaml gonadotrophin release? Definition Secretion is pulsatile Frequency and concentration critical for normal gonadotropin release Term What happens during the follicular phase? Definition Mean amplitude is lower in the follicular phase compared to the luteal phase of the menstrual cycle Pulse frequency is q90 min in early follicular phase, q60-70 min in late follicular phase, and q100-200 min during luteal phase Term What does increased frequency or amplitude of release result in? Definition Increased frequency or amplitude of release results in suppression of FSH and LH release from pituitary Term What happens if you give GnRH continously? in a pulsatile fashion? Definition shuts down system; gonadotrophins rise again. Term GnRH agonists: if given in a continuous fashion, what happens? Definition Long-acting GNRH agonists cause an initial increase in LH and FSH followed by a prolonged suppression of gonadotropin release. Down regulation of GNRH receptors on the pituitary gonadotrophs is thought to occur Term when do you give GnRH agonists? Definition Clinically used to: treat precocious puberty; prevent ovulation in ovarian stimulation as part of In Vitro Fertilization; treat estrogen sensitive conditions such as fibroids and endometriosis Term what are side effects of GnRH agonists? Definition hypoestrogen: menopause, hot flashes, vaginal dryness Term what happens if you give GnRH in a pump/pusitile fash8ion? Definition GNRH delivered in a pulse every 60-120 minutes. Effectively induces folliculogenesis and ovulation in patient with GNRH deficiency. In males with GNRH deficiency – long term pump use induces puberty and spermatogenesis Term How are FSH and LH secreted? Definition Both secreted in a pulsatile fashion by gonadotroph cells in anterior pituitary Term How are FSH and LH composed? Definition Glycoproteins composed of alpha and beta subunits Alpha subunit identical in FSH, LH, hCG and TSH Term what gives these horomones their unique activity? Definition Unique beta subunit confers these hormones the unique biologic activity Term what do these horomones do? Definition Bind to receptors in the ovary and testes to stimulate sex steroid production Term besides LH, what horomones stimulate ovulation? why? Definition LH is very similar in composition to hCG - the end organ receptor is identical (hCG administration triggers ovulation) Term what are 3 FSH functions in females? Definition FSH: Stimulates granulosa cell estradiol production by aromatase induction; Increases FSH receptor number; Stimulates growth and proliferation of granulosa cells Term What are 3 LH functions in females? Definition LH : stimulates theca cells to produce androgens (androstenedione and testosterone) which are then converted to estrogens in the granulosa cell (2 cell theory); Triggers ovulation; Stimulates progesterone and estrogen production by granulosa cells after ovulation Term In males, FSH function? Definition FSH : Testicular growth; Stimulates sertoli cells which are essential for spermatogenesis; Sertoli cells produce androgen binding protein which concentrates testosterone within the testis Term In males, what is LH function? Definition LH: Stimulates Leydig cell testosterone production; Also required for maturation of spermatozoa Term wHAT cns INFLuences can modulate GnRH secretion? Definition physical, psychological, nutritional stressors Term whare are gonadal steroids important for at the level of the pituitary and hypothal? Definition feedback Term what does estrogen do? Definition Estrogen (females) : positive feedback (induces LH/FSH preovulatory surge) negative feedback (demonstrated by suppression in FSH by postmenopausal estrogen replacement therapy) Term What do inhibins and activin do? Definition Inhibins and Activin: polypeptides secreted by granulosa cells (females) and sertoli cells (males) modify FSH secretion from pituitary (inhibin inhibits FSH, activin stimulates FSH) Term What does progesterone do? Definition Progesterone in high levels inhibits GNRH Term what is follistatin? Definition peptide secreted by the pituitary Term what does it do? Definition it inhibits FSH secretion by binding/inactivating Activin Term What does prolacting do to GnRH? Definition Prolactin - suppresses GNRH (lactational amenorrhea) Term what does CRH do? Definition CRH - suppresses GNRH (Stress response) Term what does leptin do? Definition Leptin - secreted by adipose tissue, increases GNRH (nutritional cue) Term what do opiates do? Definition Opiates – suppress GNRH (hypothalamic amenorrhea reversed by opioid receptor blocker naltrexane) Term what does melatonin do? Definition Melatonin (pineal gland) – suppresses GNRH Term what are other upstream regulators of GnRH? Definition Other upstream regulators: Inhibitory: DA, Serotonin, GABA Stimulatory: NE, glutamate, TGF-a Both inhibitory/stim: Neuropeptide Y, Kisspeptin Term when is the HPA fully functional? Definition Hypothalamic- pituitary axis begins to fully function during midgestation Term How is the HPA inhibited? Definition Inhibition by steroids in late gestation A Term what happens after birth and child hood? Definition after birth – rise in gonadotropins due to loss of negative feedback from placental steroids Central inhibitory force on hypothalamus during childhood Term what happens during puberty? Definition Pubertal rise of GNRH pulsatility Term what happens during menopause? Definition Menopause = ovarian failure with loss of negative feedback from gonadal steroids leads to increased LH and FSH Term What does the thyroid gland control? Definition The thyroid gland controls growth, development and homeostasis It also plays a major role in reproduction Term what do thyroid disorders lead to? Definition Thyroid disorders (especially hypothyroidism) are very common in women and often lead to anovulation, menstrual irregularies and amenorrhea Therefore the neuroendocrine regulation of the thyroid is important to understand Term What does TRH do? Definition TRH secreted by the paraventricular nucleus stimulates TSH secretion from the anterior pituitary Term What is TSH? Definition TSH is a glycoprotein hormone consisting of a shared alpha subunit (with hCG, FSH and LH) and a specific beta subunit TSH stimulates iodide uptake, production and release of thyroxine (T4) and triiodothyronine (T3), increased gland vascularity and size Term How do you regulate TSH? Definition TSH is very sensitive to changes in circulating thyroid hormone; TSH is elevated in primary hypothyroidism and suppressed in primary hyperthyroidism Term what does TRH do? Definition TRH stimulates prolactin secretion which in turn suppresses GNRH (may explain some reproductive effects) Term where is Prolactin formed? Definition Prolactin is a 198 aa polypeptide hormone secreted from the lactotrophs of the anterior pituitary Term what does prolactin do? Definition Prolactin stimulates breast development and lactation during and after pregnancy Term what can hyperprolactin lead to? Definition Although NOT DIRECTELY responsible for regulating gonadal function, hyperprolactinemia leads to hypogonadism-- Women: Anovulation, oligo/amenorrhea and infertility Men: decreased libido, impotence, infertility. Hyperprolactinemia suppresses GnRH Term How is prolactin regulated? Definition Prolactin is primarily under inhibitory control from arcuate nucleus of hypothalamus (Prolactin inhibiting substance = Dopamine) Conditions interfering with normal dopamine inhibition of prolactin secretion cause hyperprolactinemia damage to the dopaminergic neurons of the hypothalamus, pituitary stalk section, or drugs that block dopamine receptors on lactotroph cells (antipsychotics) Term what is prolactin stimulated by? Definition Prolactin is stimulated by: TRH (hypothyroidism) Estrogen (pregnancy, oral contraceptives) Chest wall nerve stimulation (suckling, nipple stimulation, injury to chest wall) Stress (exercise, surgery)