endocrinology Flashcards
what is the difference between exocrine glands and endocrine glands?
exocrine glands maintain connecting cells between the surface epithelium and gland cell, in endocrine glands, these connecting cells are lost
what is the main similarity between endocrine and neuronal cells?
both can be depolarised
give an example of how cells in the endocrine system respond to depolarisation
the adrenal medulla responds to depolarisation to release noradrenaline/adrenaline
explain the mechanisms of cell signalling over short distances
autocrine: hormonal signal acts back on the cell of origin/adjacent cell of same type
paracrine: hormonal signal carried to adjacent cell over a short distance via interstitial fluid
explain the mechanisms of hormonal cell signalling over long distances
endocrine: carried to distant target cell via bloodstream
neurocrine: hormonal signal originates in a neurone and after axonal transport to bloodstream, is carried to distant cell
what type of hormones are water soluble?
catecholamines, peptides/protein hormones
explain the mechanism of action for water soluble hormones
1) hormone binds to receptor, activating G-protein + stimulates adenylyl cyclase
2) adenylyl cyclase converts ATP into cAMP
3) cAMP acts as a second messenger to activate protein kinases
4) activated protein kinases phosphorylate cellular proteins
5) phosphorylated proteins trigger cellular response
what types of hormones are often lipid soluble?
steroid and thyroid hormones
explain the mechanism of action of lipid soluble hormones
1) hormone diffuses into cell
2) activated receptor-hormone complex alters gene expression
3) newly formed mRNA directs synthesis of specific proteins on ribosomes
what 3 factors are hormone levels determined by?
rate of production
rate of delivery
rate of degradation
give the cellular roles of Ca2+
- neuromuscular excitability
- coagulation
- synaptic transmission
- second messengers
- regulation of gene transcription
- coordination of metabolic activity
- bone formation
what are the cellular roles of phosphate?
- structure of membrane phospholipids
- energy metabolism
- protein phosphorylation
- genetic information
- bone formation
where is parathyroid hormone made and what is its role?
made in the principle/chief cells
increases plasma Ca2+ and decreases plasma phosphate
what are the three main target organs of parathyroid hormone?
bone, kidney, intestine
what are the main effects of parathyroid hormone on its target organs?
- causes increased osteoclast activity in the bone
- causes increased calcium reabsorption and phosphate loss in the kidney
- increases calcitriol levels in the intestine
what is the role of calcitriol? what is required for calcitriol formation?
promotes intestinal absorption of Ca2+ and PO43-. requires vitamin D as a precursor
what are canaliculi?
small structures within osteons where calcium reabsorption occurs. a labile pool of calcium
outline fast exchange of Ca2+ between bone and plasma
Ca2+ is moved from the labile pool in the canaliculi into the plasma by PTH activated Ca2+ pumps located in the osteocytic-osteoblastic bone membrane
outline slow exchange of Ca2+ between bone and plasma
Ca2+ moved from stable fluid in mineralised bone into the plasma by PTH induced dissolution of bone
what is calcitonin and where is it produced?
a peptide hormone produced by the parafollicular cells of the thyroid gland. it is secreted in response to high levels of Ca2+ and gastrin and causes decrease in plasma calcium and phosphate
what do the hypothalamus and pituitary control as a functional unit?
- body growth
- reproduction
- milk secretion
- metabolism
- adrenal gland function
- thyroid gland function
- water metabolism
- puberty
explain how the hypothalamic-pituitary axis is responsible for water homeostasis
ADH produced in hypothalamus -> transported down neurones to posterior pituitary -> ADH released into circulation
what is the role of the anterior pituitary?
produce the 7 trophic hormones; which stimulate the release of other hormones
where and how is growth hormone produced/inhibited?
anterior pituitary
stimulated by hypothalamic GHRH and inhibited by hypothalamic somatostatin
