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Hormonen en homeostase samenvatting deel1
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samenvatting voor deeltoets 1 hormonen en homeostase, UU biomedische wetenschappen 2de jaar
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By: JuliaWiersema • 5 year ago
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Hormonen samenvattingMelatonin: day-night cycles
Releasing/inhibiting hormones: regulate release of adenohypophysis hormones
ADH/oxytocin produced by hypothalamus and stored in pituitary
- Steroids (cortisol)
- (Poly)peptides (insulin)
- Glycoproteins (gonadotropins: LH/FSH/TSH)
- Amino acid derivatives (epinephrine/adrenalin)
Paracrine: hormone to extracellular fluid
Endocrine: hormone to blood, effect on distance
Autocrine: hormone acts on the cell that secreted it
Steroid and thyroid (lipophilic) hormones bind intracellular receptors which become second
messenger their selves
After interaction with GPCR:
cAMP pathway
- GDP is released from G-protein
- GTP is bound
- Part of G-protein (alpha subunit) binds to adenylate cyclase
Adenylate cyclase converts ATP to cAMP (second messenger)
cAMP activates protein kinase A (PKA)
- Phosphorylation of regulatory proteins
o Kinases
o Ion channels
Phosphodiesterase converts cAMP to AMP
Alpha subunit has GTPase activity→ converts GTP to GDP to inactivate pathway, catalysed by RGS
(regulator of G-protein signalling)
Also phosphatidylinositol pathway (IP3)
- Phospholipase C in plasma membrane is activated
- Hydrolyses PIP2 to IP3 and DAG
o IP3 binds to receptor in SER membrane and mito→ opens Ca-channels
o DAG activates PKC→ increase DAG and Ca concentrations
, Pituitary consists of a neural and epithelial part
- Rathke’s pouch= mouth part, goes up
o Becomes pars intermedia and pars distalis
o Adenohypophysis
o Anterior
o Production of 6 hormones in pars distalis:
▪ Somatotropes (GH); Lactotropes (PRL); gonadotropes (LH and FSH);
corticotropes (ACTH) and thyrotropes (TSH)
o Pars intermedia:
▪ ACTH is split by peptidases in melanotropic cells→ MSH and CLIP
- Infundibulum= brain part, goes down
o Becomes pars nervosa
o Neurohypophysis
o Posterior
o Storage of ADH and oxytocin
▪ Produced by hypothalamus
3 hormone families:
1.POMC (prohormone) gene gives 3 products
One protein is formed (no alternative splicing), the peptide is processed by different peptidases to
form different products, depending on the cell type
- Main product in corticotropic cells (pars distalis) is ACTH→ regulates activity of adrenal
cortex
o Split by peptidases in melanotropic cells (pars intermedia): main product is MSH, and
CLIP
- By-products: lipotropin and endorphin
o Ligand for morphine receptors
- Biologically inactive product
When high concentrations of ACTH are present→ MSH receptors are also triggered because the first
13 amino acids are the same= cross activation
2.Glycoproteins= peptide hormones with sugar residues. LH, FSH (gonadotropic cells) and TSH
(thyrotropic cells)→ heterodimers a- and b-subunit. Alfa subunit is identical in the 3 hormones, beta
is derived from gene duplication event and determines biological activity/specificity
- Alfa only works as a dimer
3.Somatomammotropines GH and PRL→ gene duplication, somatotropic and lactrotropic cells
- Prolactin stimulates mammaes
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