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77 Cards in this Set
- Front
- Back
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What hormones are secreted from the A.P?
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Adenocorticotropic hormone (ACTH), TSH, FSH, LH, GH, PRL
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Endocrine products of the Anterior pituitary are regulated by?
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Hypothalmic regulatory factors
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What are the secretatory cells of the anterior pituitary and what do they secrete?
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Corticotpres (ACTH) , TSSH (thyrotropic hormone) Gonadotropes (LH, FSH), Somatotropes (GH), Lactotropes (PRL)
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Which anterior pituitary cells are basophils and which are acidophils? What is prevalence for each?
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Corticotropes, thyrotropic hormone, Gonadotropes - Basophils (20%,5,10%) Somatotropes, Lactotropes (Acidophiles (50%,20% respectively)
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What synthesizes ADH and Oxytocin?
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Supraoptic and paraventricular nuclei of the hypothalamus
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What are pituicytes?
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Glial cells (astrocytes) surround axons contact processes during hormone release facilitate entry of stored hormone into fenestrated capillary. Posterior pituitary
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The communication route between hypothalamus and anterior pituitary is
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Vascular
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hormones that stimulate (or inhibit) the hypophysis, or pituitary.
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Are called hypophysiotrophic (HPT
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Parvocellular neurons release their hormones into what? and then picked up? and go to?
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Median emenience, primary capillary plexus, hypophyseal portal vein into interfundibular stalk- small- HPT very concentration way more than systemic circulation
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Branched from the portal vein are the secondary capillary plexus does what?
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Bathes cells with HPT hormones that influence their secretion.
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Unlike the anterior pituitary, the posterior pituitary
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there is a direct physical connection between the hypothalamus and the posterior pituitary: the axons of magnocellular hypothalamic neurons.
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The posterior pituitary comprises a specialized collection of terminals of
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Non-myelinated neurons, whose cell bodies are located in magnocellular neurons located in the supraoptic nucleus and paraventricular nucleus.
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The terminals of magnocellular neurons form the
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posterior pituitary or neurohypophysis.
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Lactotrophs: make prolactin (PRL). Unlike other AP hormones, PRL is tonically inhibited by hypothalamic (1a) dopamine (DA). To increase PRL secretion, dopamine secretion must decrease. Under some conditions (1b), TRH can stimulate prolactin secretion, although the role of TRH on prolactin secretion in humans is not resolved. Breast is the major target for?
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PRL, which synthesizes milk in response to PRL.
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GH target tissues include and is regulated by
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Liver bone and fat, IGF1, somatostatin
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Anterior pituitary
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Are called hypophysiotrophic (HPT) hormones
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What makes TSH, by who, and what does it do?
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Thyroptric stimulated by TRH, and produces T3/T4 in thyroid
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LH and FH are made by and response to?
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Gonadotrophs stimulated by GnRH
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Gonads make what in response to what homorome?
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Gonads make inhibin in response to TSH
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What is the precurser to ACTH?
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POMC
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What stimulates corticotrpohs?
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CR AVP
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target for ACTH is adrenal cortex, which synthesizes?
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cortisol
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The adrenal also makes dehydroepiandrosterone (DHEA) an androgen, in a process that is stimulated by ACTH, and aldosterone, a mineralocorticoid (that promotes sodium reabsorption by kidney), whose synthesis is primarily controlled by the renin-angiotensin system and NOT by ACTH.
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KNOW
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Anterior pituitary derives from?
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Rathke’s pouch.
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What determines AP secretion?
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Integrated inhibitory and stimulatory HPT inputs determine net AP secretion.
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Negative feedback occurs when concentrations of a target tissue hormone reach a and then does what?
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threshold set point, and act on the pituitary or hypothalamus to decrease the signals for AP hormone secretion
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Positive feedback of anterior pituitary hormone secretion only occurs for
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LH and FH
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How does local negative feedback within the hypothalamic/pituitary axis (short-loop feedback):
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AP hormone directly feeds back upon HPT neurons, modifying HPT hormone secretion (examples include growth hormone and prolactin).
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Ultra-short loop feedback
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HPT hormones locally modulate their own secretion.
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Anterior pituitary hormones are or are not continuously released?
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Are not -pulsatile
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What is pulsatile secretion important in the AP?
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Target tissues can become desensitized if they’re exposed to high concentrations/long duration of a hormone; pulsatile secretion can prevent desensitization.
Physiological information can be relayed by frequency or amplitude of hormone pulses |
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What affects the amplitude modulation?
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Varying the amt of hormone released at each burst
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What affects the frequency of the pusle?
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Number of bursts per alotted time interval
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Which hormone secretes differently from other A.P hormones and how?
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Prolactin differs it is under tonic inhibition by doapmine. Decrease DOPA to increase prolactin
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Suckling does what to dopamine levels?!
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Decreasing them, increasing prolactin
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Hypothyroid patients with an elevated TFH may present with?
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hyperprolactinmia
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Prolactin exhibits what kind of feedback?
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Short loop feedback - of its own secretion by stimulating hypothalmic dopadenergic neurons to mk and secrete DOPA -inhibiting prolactin
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Hyperprolactinemia (elevated prolactin secretion) is normal in
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lacatation
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IGF inhibits
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GH, by inhibiting somatotrophs, ghRN, and increases somatostatin
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defects in IGF-1, or IGF-1 receptors can cause?
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dwarfism!
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What are the glycoprotein hormones?
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LH FSH hCG
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Thyroid hormones are tyrosine-derivatives named for the number of iodides covalently attached (these iodides determine hormone activity). T4 (thyroxine) is a precursor to T3 (3,5,3’-tri-iodothyronine), the active hormone; where is T3 made?
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T3 is made by thyroid, liver, pituitary, and other tissues.
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T3 negative feedback ?
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T3 inhibits regulates TSH secretion primarily at the thyrotroph, and also by decreasing hypothalamic TRH.
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If thyroid function is deficient and thyroid hormone synthesis compromised, why do TRH and TSH levels increase ?
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Loss of negative feedback
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Positive feedback secretion of LH and FSH triggers what?
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ovulation.
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Inhibin is a gonadal protein hormone that selectively inhibits?
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FSH (but not LH) in men and women.
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ACTH stimulates cortisol synthesis by?
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adrenal fasciculata.
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What is the only endogenous negative feedback regulator of ACTH secretion, decreasing
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Cotisol, ACTH at pituitary corticotrophs and
CRH and AVP synthesis and secretion in the hypothalamus. |
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ACTH is cleaved to αMSH, which regulates in many animals what?
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pigmentation
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oxytocin receptors and vice versa
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but appreciate that because of this sequence similarity, there is some overlap in the function of these hormones: for instance, high concentrations of AVP can stimulate
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Damage to the posterior pituitary or mutations in vasopression gene can cause
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diabetes inspidius
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Vasopressin prevents
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prevents diuresis
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Increased plasma osmolality (as little as 1-2%) is sensed by
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sensed by osmoreceptors in the hypothalamus
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Decreased plasma volume (>5-10% decrease) is initially sensed by
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by stretch receptors (baro-receptors) in the great veins entering the right atrium. Greater reductions in plasma volume decrease blood pressure and reduce the stretch of receptors in the carotid sinus and aortic arch
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signals activate neuronal relays that stimulate SON and PVN magnocellular neurons to secrete
Vasopressin (ADH)? |
Increased plasma osmolality Decreased plasma volume
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What stimulates reabsorption of urea in inner medullary collecting ducts via urea transporters, important in establishing osmotic gradients
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ADH
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Reabsorbed water restores plasma osmolality, a negative feedback signal decreasing ADH secretion.
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change tomorrow
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xcessive alcohol consumption can?
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nhibit vasopressin secretion, leading to diuresis.
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Cells that have just degranulated in the A.P. or are un differentiated stem cells are called?
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Chromophobes
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THe major cell of the P.P is?
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The pituicyte
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In the P.P the cell that supports unmylenated axons which have expanded axon terminals that have granules called?
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herring bodies
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Herring bodies are what? That contain what?
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Herring bodies are granules in the axon terminal of pituicytes that contained oxytocin and ADH
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FSH and LH both work on what ? What do they do respectively?
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FSH and LH both work on testis and ovaries. FSH =spermatogensis, and follicular development (estrogen secreting) LH =androgen secretion, ovulation progesterone secretion
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The thyroid gland is made up of?
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two lobes connected by a isthmus
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the two major secratory products of the thyroid are?
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Thyroid hormone and calcitonin
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What cell secretes thyroid hormone?
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Follicular cells (most abundant in thyroid)
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What cells secrete calicitonin?
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Parafollicular cells (C cells in thyroid - larger than follicular cells)
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Where, how many, what do they do these parathyroid glands? Embrologically where do they come from?
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The 4 Parathyroid glands are in the thyroid, posterior fascial sheath, they secrete PTH - HUGE in Ca homeostatisis, come from 3 and 4th pharyngeal pouches
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Describe what happens when serum Ca drops?
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Parathyroid increase PTH - 1. Increase Bone resorption ->increase serum Ca. 2. Increase Renal Ca reabsorption -> increase serum Ca, ADDITIONALLY Renal Ca reabsorption increases Vit D, increases GI reabsoprtion of Ca, increase serum Ca.
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How many ways can the parathyroid increase serum Ca?
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Three ways--> increase PTH 1. bone, 2. Kidney 3. GI
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What cells secrete PTH, what do they look like?
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Chief cells secrete PTH - small, small nuclei, polygonal
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Oxyphil cells are in what gland? Function? Characteristics?
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Found in Thyroid, unknown function, increase w age and have alot of Mt (esinophilic)
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Adrenal glands embrologically arise from?
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Cortex from mesoderm, Medulla from neural crest
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The cortex secretes what and the medulla secretes?
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Cortex - steriods, Medulla- catecholamines
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Adrenal cortex layers are? What do they secrete?
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Zona glomerulosa (aldosterone), Zona fascilulata (cortisol), zona reticularis (sex hormones - DHEA) SALT, SUGAR, SEX
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What does the pineal gland do? How?
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Regulate diurnal rhythms. Pinealcytes secrete melatonin. Glial (supporting cells 5%)
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What is the unique characteristic of the pineal gland? Where is the gland located? Origin?
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Brain sand (increases w age - concretion calcifications) Pineal is located near the 3rd ventricle. Origin neuroectodermal
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