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24 Cards in this Set
- Front
- Back
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where's the pituitary?
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you know where
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what does the pituitary look like?
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*posterior part is an extension of the brain (neurohypophysis)
*anterior part gets brain input from neurohormones through portal circulation |
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explain the 2 parts of the pit.:
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*Anterior: “adenohypophysis” originates from Rathke’s pouch (pharyngeal epithelium); neurons from the hypothalamus secrete releasing factors directly into portal vein to regulate pituitary hormone synthesis and release
*Posterior: “neurohypophysis” originates from neural tissue (extension of hypothalamus); consists of axons of neurons from the supraoptic and paraventricular nuclei that deliver hormones to posterior lobe for release |
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Molecular Regulation of Pituitary Development (chart):
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*initial factor: HesX-1; acts on stem cells to start anterior pituitary development
*CRH-->ACTH *HesX-1--> PROP-1 --> PIT-1 *PROP-1 --> FSH/LH *PROP-1 suppresses HesX-1 *Mutations in HesX-1 halt this process! Called "multiple pituitary hormone deficiency" You only see the posterior pituitary in these patients. |
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Molecular Regulation of Pituitary Development:
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Transcriptional activators direct embryonic development of the anterior pituitary; inactivating mutations produce multiple pituitary hormone deficiencies (MPHD)
Expression of HESX1 gene is very early (stem cells); role in optic nerve and anterior pituitary development PROP1 is also early, required for repression of HESX1 and is prerequisite for PIT1 PIT1 discovered as activator of GH promoter; expressed throughout life |
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stuff the pit makes:
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Anterior Pituitary Cell Types:
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*Somatotrophs- GH-secreting cells, make up ~50% of the cell mass
*Lactotrophs- PRL-secreting cells, make up ~10-25% of the cell mass; proliferation accounts for increase in pituitary size during pregnancy *Thyrotrophs- TSH-secreting cells, make up <10% of cell mass *Corticotrophs- ACTH-secreting cells, make up 15-20% of cell mass *Gonadotrophs- LH and FSH-secreting cells, making up 10-15% of cell mass |
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Hypothalamic Releasing Hormones:
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*Regulate Anterior Pituitary Hormones
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Anterior Pituitary Hormones 3 Major “Families”:
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*GH/Prolactin
Single chain polypeptides Internal disulfide bridges *TSH/LH/FSH Glycoproteins: share an alpha subunit Unique beta subunits HCG (made in placenta) *POMC (pro-opiomelanocortin) Hydrolyzed into ACTH, ß-endorphin, MSH |
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regulation of GH secretion:
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releasing factor- GHRH
inhibitory factor- Somatostatin target tissues- liver, muscle, fat, bone (mostly liver) feedback- IGF-1 feedback to pit and hypothalamus |
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Normal daily secretion of GH:
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Normal lifetime secretion of GH:
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Regulation of GH (more complex boney slide)
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*stomach--> empty stomach--> ghrelin--> more GH (positive feedback)
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Actions of Growth Hormone:
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IGF-1 has a role in all these tissues EXCEPT adipose tissue
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Functions and Regulation of GH (text):
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*Regulation:
Hypothalamic: GHRH, SMS; pulsatile overnight Peripheral: IGF-I (somatomedin), Ghrelin Irregular/intermittent release during sleep *Activation: Hypoglycemia, starvation, exercise, stress, sleep *Action: Direct (1) vs Indirect (2) 1. Metabolic: lipolysis, protein synthesis, insulin resistance 2. Growth: IGF-I *Mechanism: GHBP/GH Receptor dimerization |
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interaction of GH with receptors:
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ALP= Acid labile subunit
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Overview of prolactin secretion factors:
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releasing factor- TRH
inhibitory factor- Dopamine (more potent than TRH!) target tissues- breasts (milk production/release) feedback- prolactin (decreases dopamine) |
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Prolactin Regulation and Action:
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*Regulation:
-Tonic inhibition by dopamine (neurons in hypothalamus and posterior pituitary) -Stimulated by pregnancy, breast feeding, TRH -PRL increases DA (negative feedback) *Action: -Proliferation, branching mammary ducts during puberty -Growth, development mammary alveoli in pregnancy -Milk production: suckling (positive feedback) |
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talk about that posterior pituitary...
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*Extension of Hypothalamus
*Terminal nerve fibers from hypothalamic supraoptic and para-ventricular nuclei *Transported by carrier protein (neurophysin) to nerve terminals in posterior pituitary and released from granules by exocytosis into circulation *Vasopression (ADH): water, BP *Oxytocin: milk letdown, uterine contraction |
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Vasopressin:
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*9 amino acid peptide, AVP, synthesized primarily in supraoptic nuclei, transported/stored posterior pituitary
*Controlled by -osmolality (osmoreceptors in hypothalamus) -vascular volume/pressure (baroreceptors in heart) *Receptors determine action: 1. V1 aka V1a (vessels: vaso-constriction) 2. V2 (renal tubule: water re-absorption, sic “anti- diuretic hormone”; also increases factor VIII) 3. V3 aka V1b (corticotrophs: increase ACTH secretion) |
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effect of plasma osmolality on ADH:
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-makes you thirsty
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effect of blood pressure on ADH:
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-takes a huge loss of pressure to elicit ADH
-osmolality has a greater effect on ADH than pressure |
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Vasopressin (AVP) Mechanism of Action:
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*classic G PRO coupled receptor.
*AQP2= aquaporin 2 *ADH uses AQP2 to move H2O from urine to plasma. |
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problems you can have or acquire related to Water Regulation (Diabetes Insipidus):
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Central DI: you don't make ADH
nephrogenic DI: the problem is in the kidney |
