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Terms in this set (35)
Afferent nerve signals to hypothalamus. Nerve axons. Produces factors- neurotransmitters and peptides transferred to blood system.
Capillary netork, releases hormones (tropins) by veins to systemic blood
Posterior pituitary hormone release
Release of posterior pituitary hormones (vasopressin, oxytocin) by veins to systemic blood.
Biosynthesis of neurotransmitters
Produced by brain and periphery. Some can be measured in blood, some not at all. Norepinepherine is similar to epinephrine, only demethylation separates them-->short halflife. AA source of GABA is glutamate.Tryptophan precursor to serotonin.
Short peptides produced by hypothalamus
Produces 10-15 releasing facotres. All peptide structure. Never longer than 40-50 AA, most 3-4. Some releasing factors, some inhibitory. Short half life. TRH is 3 AA, GnRH 10AA. Somatostatin inhibitors of GH (TRH, insulin and alnmost every other hormone), produced by delta cells of pancrease.
Thyroid Releasing Hormone
3 AA long: Glu-His-Pro, with altered structure, carboxy end blocked by amine group forming amide bond, amine end altered into pyro ring which makes it unrecognizeable to cleavage. Aminopepsidase eats from N-end, carboxypeptidase eats from C-end.
Short peptides produced by posterior pituitary
Human oxytocin and vasopressin (ADH). ADH important in absorbing urine from kidney. Diabetes insipitus is total loss of ADH, water loss cannot be replenished by regular IV. DDAVP is pharmacological analog of ADH, Arg replaced by D-Arg.
Anterior pituitary large polypeptides
Signal from RH from hypothalamus. Glycoproteins-sugar moiety with 2 chains. Gonadotropins (RSH and LH), and TSH. Single chain polypeptides: 1 peptide ~200AA with glycoproteins, GH, ACTH, Prolactin. Prolactin sometimes measured for cross reactivity with GH ex: acromegaly shows hyperprolactinemia.
Alpha subunit of nterior Pituitary Hormones (APH): LH, FSH, hCG, and TSH
Similar in all an APH. Final changes can't depend on it. Needed for function of protein but interchangeable.
Beta subunit of Anterior Pituitary Hormones (APH)
Charges are characteristic but won't bind to receptor alone, but high (40%) homology. Structure established only when bound to alpha subunit. Need both for function but beta subunit of FSH + alpha unit of TSH=FSH. Assay must be specific to this.
Glycoproteins in Anterior Pituitary Hormones
FSH, LH, and TSH (HCG): each composed of alpha and beta subunits. Alpha common to all, beta unique. 30% carbohydrate surrounds proteins, produce shield of molecule, if remove glycosides, peptide is active but halflife decreased.
Anterior pituitary release
Stimulates testes, ovaries, thyroid to produce other hormones. Hormones are function of stimulation.
Hypothalamus effect on GH
Can be releasing (GHRH) or inhibiting (somatostatin).
Growth Hormone (GH)
Stimulating hormone. Itself has some function but mostly stimulates liver and other glands to produce IGF-1. Affects tissues and many cells
Negative feedback of releasing factors and production of GH (hypothalamus and pituitary).
Produced by long peptide: Pro-Opio-Melano-Cortin of 200 amino acids. Contains different activities, can be divided into 3 peptides: N-terminal, ACTH, beta-Lipotropin (endorphins and enkephalins). Increased size of molecule is greater halflife because less susceptible to proteolytic damage.
Steroid organizes glucose production during stress. Addison's dieasese is a lethal lacking of cortisol.
Somatostatin activates or inhibits the pituitary gland, which activates Thyrotropin, which activates the thyroid gland. T4 and T3 from the thyroid provide negative feedback to the pituitary and to TRH in the hypothalamus.
Structure of thyroid hormones and steroid hormone
Stable, long halflife, not soluble in water, brought to membrane and enzymes embedded in lipid structure.
Prohormone, 2 ring structure from tyrosine with an oxygen bond. Activated to become tridothyropyruvic acid. Needs iodine and enzyme action from the membrane to activate.
Hypothalamic-Pituitary-Gonadal Axis in the female
GnRH activates the pituitary gland which releases LH and FSH to activate the ovaries, which ovulate and release steroid hormones (estradiol, progesterone), which provide negative feedback to the pituitary gland and the hypothalamus.
Hypothalamic-Pituitary-Gonadal Axis in the male
GnRH in the hypothalamus activates the pituitary gland which activates LH and FSH , which activate the testes for spermatogenesis and release of testosterone and inhibin, which negatively feedback to the hypothalamus.
CRH in the hypothalamus activates the pituitary gland to release corticotropin/ACTH, which activates the adrenal glands (endorphins, endocrines, and ACTH), which release cortisol to negatively inhibit the hypothalamus.
How many rings are in the basic steroid ring structure?
What is the difference between gonadal steroids?
Testosterone is converted to estradiol by aromatization of the A ring.
Pharmacological drugs that inhibit estroginase activies dependent on aromatic character of hormones.
Testing for Cushing Syndrome (excess of Cortisol)
Measure 2 samples, one and night (should be lower) and one early morning (should be highest). Differentiation between the 2 give answers to see if cortisol follows ACTH levels.
Hormones affected by stress
Measurement of growth hormone
Discrete values not useful: need to take 20 measurements, 1 every 10 minutes for about 6 hours.
In hypothalamus, LHRH oscillator (pulse generator), frequency coded largely synchronous intermittent discharge.
In portal vessels, hormonal signal pulsatile
in pituitary gland, frequency and amplitude modulated
Signal, pulsatile secretion, activation of gonadal gonadotropin receptors, from pituitary
From gonads, amplitude modulated, peptide hormobe feedback via inhibink, testosterone and estradiol act via steroid receptor.
Exogenous GnRH and LH and FSH
continuous administration of GnRH suppresses plasma LH and FSH. Secretion is reestablished after pulsatile administration of GnRH. Ova releasted at different maturation rate, stimulates growth-->100x more successful IVF.
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