Endocrine System Flashcards
3 different ways endocrine cells cluster together
- 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
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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