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