Endocrine Day 1- HPA relationship Flashcards Preview

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Flashcards in Endocrine Day 1- HPA relationship Deck (45)
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What is an endocrine hormone?

  • Substance released from ductless gland into circulation so it can be carried to site of action
  • endocrine system is slow to act and longer lasting compared to neurotransmitters.
    • also endocrine hormones released in larger quantity
  • Endocrine hormones help maintain homeostasis
  • nervous system can perpetuate and magnify response of endocrine system


What is a neuroendocrine hormone?

  • Neuron releasing neurohormone into a blood vessel
  • Example is HPA system (hypthalamus-pituitary)
    • rapid response by hypothalamic releasing hormone, longer lived response by activation of pituitary hormone release
      • pituitary hormones then target other glands and they in turn make their own hormone. 
        • This is called the multiplier effect


What is a paracrine hormone?

  • Hormone released from one cell to act on cell nearby either directly (going directly to cell) OR via blood stream
  • Can be autocrine as well.
    • hormone released can influence cell which released the hormone


How do lipophilic hormones function?

  • Lipophilic hormones are able to easily diffuse into cell membrane by concentration gradient
  • Once inside cell either:
    • 1) attach to cytoplasmic receptor (intracellular receptor)
      • hormone-receptor complex diffuses through nucleus and binds to DNA
    • 2) Diffuse through cytoplasm through nuclear membrane on its own


How do hydophilic hormones function at celluar level?

  • Bind to membrane receptors
    • can't readily pass through lipid bilary of membrane
  • linked to second messaenger systems inside target cells
    • see elevation in cAMP, Ca, or other second messenger systems.
      • influence cellular activity on nuclear level
      • specific proteins produced (enzymes, protein hormone, structural proteins, etc)
      • this causes effect on cell to make a biological response


How do thyroid hormones work?

  • Lipophilic in nature
    • composed of aromatic amina acid
  • easily pass through cell membrane  and nuclear membrane to have effect on cell.


How does the second messenger systems work?

  • Water soluble (hyrophilic) hormone binds to external plasma membrane receptor, alter G protein in membrane of target cell
  • Activate PIP--> IP3, DAG
  • Results in intracellular stores of Ca
    • activates kinase enzymes, causing phosphorylation of proteins, enzymes and activates them
  • Drives some physiologicla response
  • Also, can directly affect Ca channel to allow Ca to come into cell
  • this is how hormones have physiological function


What is home to the neuroendocrine system?



What things does the hypothalmaus monitor?

  • Body temp
  • immune cell products (cytokines)
  • hormone levels secreted by endocrine galnds
  • monitoring elecytrolytes
  • stress hormones
  • reproductive hormones


What is released by the medial preoptic nucleus?

  • Master sex hormone of body


way to remember: you check someone out before (pre) with your eyes (optic). Checking someone out makes the master sex hormone (LHRH AKA GnRH)


What does the anterior hypothalamic nucleus make?

  • Thyrotropin-releasing hormone (TRH)
    • master metabolic hormone- regulates thyroid

way to remember: thyroid sits on the anterior portion of your trachea, TRH is released from anterior hypothalamic region


What is released from paraventricular nucleus?

  • Corticotropin releasing hormone (CRH)- master stress hormone
  • Oxytocin
  • Vasopressin

sister nucleus is supraoptic nucleus.


way to remember: The paraventricular nucleus has a sister named supraoptic nucleus. Both sisters have twins named ADH and oxytocin. Paraventricular also has a son named CRH and it's stressful having a son. 


What does the supraoptic nucleus release?

  • Oxytocin
  • Vasopressin


What does the periventricular nucleus make?

  • Somatostatin- primary inhibitory hormone
    • inhibits GH secretion from anterior pituitary

way to remember: Peri S.S. officer has a baricade that inhibits growth hormone


What does the ventromedial nucleus secrete?

  • GHRH- growth hormone-regulating hormone

way to remember: On ventromedial location on a guy are pecs. Guy trying to make pecs grow from GHRH


What is secreted from arcuate nucleus?

  • GHRH
  • Dopamine (not a neuropeptide but a catecholamine)
  • LHRH

way to remember: (warning, crude) Arucate is "arching" under ventromedial like a banana hammock. Guy wearing banana hammock is secreting:

  • GHRH (to grow...)
  • LHRH (master sex hormone)
  • Dopamine (happy hormone)




What is the median eminence?

  • Basal most portion of hypothalamus
  • Extension of pituitary stalk and pituitary gland
  • Where all neurons coming out of nuclei of hypothalamus (containing inhibitory and releasing hormone) terminte. 
    • median emminence contains nerve terminals and blood vessels, joining together


What are some other names for the posterior pituiatry?

What does it contain?

  • AKA Neural lobe, neurohypophysis
  • contain neurons with oxytocin and vasopressin


What are some other names for the anterior pituitary?

What is it made of?

  • Adenohypophysis or pars distalis
  • Epithelial cells developed from top of palate (rathke's pouch)

​Way to remember: think top of palate is your adenoids, the anterior pituitary forms from tissue on top of palates, therefor also called adenohypophysis


What is the sella turcica?

  • "turkish saddle"
  • where pituitary sits in sphenoid bone


What can happen if a tumor is so large, it pushes the pituitary upwards?

Loss of vision d/t the compression of the optic chiasm/optic nerve directly above pituitary


What is a macroadnemoa, microadenoma and how are they each treated?

  • Macroadenoma >10 mm
    • Causes mechanical damage to other anterior pituitary cells in gland, causing hormonal deficits
    • typically a pituitary tumor oversecretes one hormone (or maybe more)
    • typically need to be surgically removed
  • Microadenoma <10 mm
    • typically only causes overproduction of a hormone (prolactin, GH production most common)
    • typically medically/pharmacologiclaly managed with somatostatin


Why is somatostatin used to treat pituitary tumors?

  • Anytime somatostatin is active, it's inhibitory
    • has receptors all over the body
  • somatostatin and analogs developed into drugs ot control tumor growth. Can treat microadenomas. helpful if it's overproducing growth hormone


What is the blood supply for the anterior pituitary?

  • Internal carotid artery--> superior hypophyseal artery-> primary capillary plexus--> long portal veins--> secondary capillary plexus--> sinusoids--> anterior pituitary cells 
  • The blood around anterior pituitary is venous blood 
    • more susceptible to loss of perfusion with drops in BP


What is the blood supply to the posterior pituitary?

  • Internal carotid artery--> inferior hypophyseal artery--> posterior pituitary
    • supplied by arterial blood (unlike anterior pituitary)
  • since it is provided by arterial supply, smooth muscle can vasoconstrict and autoregulate the flow (upto a point) with decreasing BP
  • Posterior pituitary mainly contains neurons and is much less vascularized compared to the anterior pituitary


What kind of junction is in median eminence?

Neuron-capillary junction

  • Has dnse material- nerve terminals which contain releasing factors hormones, in direct contact with capillary lumens
    • capillary lumens have endothelial cells
      • form gap junctions
      • allow solutes to pass from blood to neural tissue and defeat BBB
      • Allows hypothalamus to monitor concentraiton of solutes in blood stream


What do the fenestrated capillaries in the median eminence allow? 

Allows particle to pass form blood to neural tissue- no BBB here


What are circumventricular organs?

  • Organs where the BBB does not exist
  • One's we're concerned about are:
    • Neurohypophysis (posterior pituitary)
    • OVLT- Organum vasculosum of lamina terminalis
    • Median eminence

way to remember: nom nom nom passes the BBB. "eats" up the blood


What is the pathway of a most typical type of hypothalmaic neuron?

  • Produces hypothalamic releasing hormone. Cell body in one of the hypothalmic nuclei with axonal projections onto the primary capillary plexus of the median eminence
  • releases neuronal contents into blood vessels
  • Lumpkin called these "hypophysiotropic neurons" in class


What is another type of hypothalamic functional unit besides the hypophysiotropic neurons?

  • Neurons that carry oxytocin/vasopressin from paraventricular or supraoptic nuclei, down into neural lob (posterior pituitary)


What are some characteristics of oxytocin/vasopressin?

  • Both composed of 9 aa, differing by only 2 aa
    • also called nonapeptides



Where does oxytocin act?

Smooth muscle- uterus, breast (let down for milk production)


What causes stimulation fo ADH secretion?

  • Extracellular fluid osmolality increase
  • volume decrease
  • pressure ecrease
  • CSF increase
  • pain
  • stress
  • temperature increase
  • b-adrenergic agonist
  • Drugs
    • nicotine
    • opiates
    • barbitutartes
    • sulfonylureas
    • antineoplastic agents


What causes ADH inhibition?

  • Temperature decrease
  • alpha adrenergic agonist
  • ethanol
  • cortisol
  • thyroid hormone


What does GHRH stimulate from anteior pituitary? What are the cells stimulated called?

  • GHRH releases GH
    • somatotrophs- cells that release GH
      • elevates cAMP, causes proliferation of somatotrophs


What does SS cause in the anterior pituitary?

  • Inhibits GH and TSH
    • inhibits cAMP
    • Inhibits cell production
    • inhibits cAMP, inhibits cellular activity


What does TRH stimulate in anterior pituitary? What are the cells activated called?

  • TRH (thyrotropin releasing hormone) releases TSH (thyroid stimulating hormone) from anterior pituitary
    • thyrotrophs- cells that secrete TSH
  • TRH also stimualtes prolactin secretion but NOT major physiological hormone


What effect does dopamine have on anteior pituitary?

  • Dopamine is inhibitory towards prolactin
    • What would happen in neurons producing dopamine were blocked/destoryed?
      • Increase in prolactin levels


What s GnRh (aka LHRH)'s effect on anterior pituitary?

  • LHRH stimulates LH/FSH prodcution
    • gonadotrophs- cells that produce LH/FSH


What is corticotropin-releasing hormone's role in anterior pituitary?

  • CRH stimulates cells making ACTH
    • Corticotrophs- cells release ACTH


The only significant physiological significant stimulator and inhibitory is ___ ___ 

growth hormone


What is long-loop negative feedback?

  • When hormone released from target cells goes back to pituitary and hypothalamus to inhibit further secretion
  • blood-borne mediated 


What is short loop negative feedback?

  • When hormone released from pituitary feeds back on hypothalamus and stops further increase
  • blood borne mediated.


What is ultra short loop negative feedback?

  • When axonal collaterals off releasing hormone neuron goes back and inhibits further activity of neuron
  • nueronally mediated (basis for pulastile anterior pituitary hormone secretion)


Every pituitary hormon is ____ in nature. Why?


  • This prevents overstimulation and desensitization
    • allows episodic release of hormone
    • hormones never are released, with hormonal levels continuously high, unless something is wrong