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Flashcards in Endocrine System Deck (45):

3 different ways endocrine cells cluster together

1. within a distinct organ (thyroid) 2. clusters of cells within other organs (pancreas) 3. extensive array of dispersed cells (GI neuroendocrine)


endocrine organs are ductless glands



what are neuroendocrine cells?

neurons within the brain that produce neurohormones and release them into the blood stream


what determines hormone specificity?

the receptors determine the specificity of the endocrine system


describe paracrine and autocrine secretions

local hormones released into the interstitial fluid. paracrine secretions act on nearby cells, autocrine reacts on the cells that released them


what are the 4 groups of hormones

proteins (insulin, HGH), small peptide molecules (vasopressin), steroids, amino acid derivatives and arachidonic analogs (adrenaline, noreadrenaline, thyroid hormones


describe how the solubility of a hormone affects its receptors

water soluble hormones link to membrane receptors and second messenger systems. lipid soluble hormones can move through the membrane and often bind nuclear receptors


under what circumstances would you get up and down regulation?

down regulation- excessive hormone, lower sensitivity. up regulation- lacking hormone, raised sensitivity


what are the primary endocrine organs?

pituitary, thyroid, parathyroid, adrenal, and pineal glands


what are the secondary endocrine organs?

hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach, liver, small intestine, skin, heart and placenta


describe the differing embryologic origins of the hypophysis

neurohypophysis- posterior lobe. develops from the diencephalon and adenohypophysis (anterior lobe) develops from the oral cavity (Rathkes pouch)


how do hormones reach the posterior pituitary?

hypothalamo-hypophyseal tract. transmits oxytocin and ADH from supra optic and paraventricular nuclei in hypothalamus to Herring bodies (neurosecratory granules)


what are the 3 parts of the adenohypophysis?

pars distalis- largest, containing the secretory cells. pars tuberalis surrounds the infundibulum. vestigial pars intermedia- remnants of rathkes pouch.


describe 3 ways hormones can interact with another

permissiveness- one hormone is necessary for another to be effective. synergism- amplify the effects of each other. antagonism- opposite effects


what are 3 general stimuli that control hormone release?

humoral stimuli- responses to changing blood levels of specific solutes. neural stimuli- respond to nerve impulses. hormonal stimuli- respond to other endocrine glands


what are the 3 parts of the adenohypophysis

median eminence, infundibular stem, pars nervosa


what are the chromophil cells and where are they found?

they are found in the adenohypophysis. they are granules with acidophils and basophils


what are the 2 classes of hormones in the adenohypophysis?

tropic and nontropic. tropic- ACTH, TSH, FSH, LH. nontropic- HGH and prolactin


what are the 3 types of basophils in the adenohypophysis

gonadotropes, thyrotropes, and corticotropes


what are the 2 types of acidophils in the adenohyophysis?

somatotropes and mammotropes- secrete HGH and prolactin


most hormones are controlled with negative feedback. which one is controlled by positive feedback?

oxytocin- stretching of the cervix causes more oxytocin


what hormone stimulates the anterior pituitary to release its thyroid hormone?

TRH from the hypothalamus


what is the hormone that the anterior pituitary releases in response to TRH? what does it do?

TSH. Stimulates secretion and production of thyroid hormones


what is the characteristic morphology of the thyroid

large follicles filled with colloid and bordered by follicular cells


how is the follicular cell indicative of thyroid activity

squamous- inactive; columnar- active


describe the storage and release of thyroid hormones

they are stored as a colloid in the follicles in a form called thyroglobulin, which is rich in iodinated tyrosine. when the thyroglobulin is reabsorbed from the follicle, the cell breaks down the thyroglobulin into T3 and T4, which are the hormones


what are the important functions of the thyroid hormones?

maintain basal metabolic rate, regulate heat production, influence body and tissue growth, play a role in development of the nervous system


what are the 3 hormones the thyroid produces?

t3, t4, calcitonin- produced by the parafollicular cells


how many parathyroid glands are their usually?



are the developmental origins of the thyroid and parathyroid the same?

no- para develops from pharyngeal pouches. thyroid from the base of the tongue.


what are the 2 cell types in parathyroid

oxyphils- large, acidophilic cells with unknown purpose that increases in number with age. chief cells secrete PTH


what does parathyroid hormone do?

increase blood calcium levels by increasing osteoclast activity


differentiate between the functions of the zone glomerulosa, fasciculata, reticularis in the adrenal cortex

glomerulosa- clusters of aldosterone secreting cells, fasciculata- columns of cortisol secerting cells, reticularis-produces weak androgens


which hormone is a glucocorticoid and which is a mineralcorticoid?

gluco- cortisol, mineral- aldosterone


what stimulates glucocorticoid secretion?

ACTH stimulates cortisol release


what do glucocorticoids do?

triggers breakdown of lipids, carbs, and proteins in most tissues


what stimulates mineralcorticoids?



what does angiontensin do?

increase absorption of Na and Cl


what does the adrenal medulla derive from?

neural crest cells


what does the adernal medulla secrete?

epinephrine and norepinephrine


how is the blood flow for function of the medulla?

one blood flow goes directly to the medulla, the other is a portal system that picks up glucocorticoids, which is essential for the methyl transferase enzyme which converts norepinephrine to epinephrine


what does the pineal gland develop from?

the roof of the diencephalon


what does the pineal gland produce?

melatonin- important for circadian rhythms


what is meant by the endocrine pancreas?

most of the pancreas is exocrine. endocrine refers to the islets of langerhans


what are the 4 different cell populations and what do they produce?

alpha (peripherally located)- glucagon- increases blood glucose, beta- insulin (centrally located)- decreases blood glucose, delta- somatostatin- inhibits glucagon, insulin, GH and TSH and HCL in stomach. F cells- pancreatic polypeptide- stimulates gastric cheif cells, inhibits bile and pancreatic exocrine secretions, decreases intestinal motility