Lecture 33 - Endocrine 3 Flashcards
(40 cards)
what is the collective name for the hormones dopamine, adrenaline and noradrenaline?
catecholamines
which nucleus of the hypothalamus is at the bottom nearest to the pituitary?
the arcuate nucleus
what is the full name of the vascular system linking the hypothalamus to the pituitary?
hypothalamus pituitary portal circulation
which endocrine organ is directly linked to the sympathetic nervous system?
the adrenal glands
- nerve stimulation the response is quicker
- blood hormone transport gives a slower, more sustained response
true or false, the thyroid gland is highly vascularised
true
- they sense the blood and release hormones into the blood
what are thyroid follicles?
sac made of cells that is filled with colloid
- peroxidase enzymes fill follicle (lots of oxidation) which allows a colloid iodine to be added to a tyrosine to turn it into thyroxine (T4) or triiodothyronine (T3)
why do we have thyroid follicles?
so the peroxidase enzymes are kept separate from the blood and the rest of the body
what does the thyroid do?
control of metabolism and body temperature
describe how T3 and T4 is synthesised
- follicular cell synthesises enzymes and thyroglobulin for the colloid
- Na+ and I- is brought into the follicular cell and through into the colloid
- enzymes add I- to tyrosines in thyroglobulin, making T3 and T4
- thyroglobulin is taken back into the cell
- intracellular enzymes separate T3 and T4 from the protein
- free T3 and T4 enter the circulation
where does thyroid stimulating hormone TSH act?
controls the:
- influx of iodine into follicular cell
- production of thyroglobulin and enzymes
describe the feedback loop that leads to TSH production
nuclei in hypothalamus release TRH after sensing low T3 and T4 levels in the blood, which travels via the hypothalamic pituitary portal circulation to the anterior pituitary, which causes secretion of TSH, which causes increased T3 and T4
what are C cells?
endocrine cells in the thyroid which sense Ca2+ levels and lower circulating calcium when levels are too high by releasing calcitonin
how does calcitonin reduce Ca2+ levels in the circulation?
inhibiting osteoclast activity (no Ca2+ release)
stimulating Ca2+ ion secretion at the kidneys
which hormone opposes the action of calcitonin?
parathyroid hormone
where are the parathyroid glands located?
posterior thyroid
what does parathyroid hormone do?
when Ca2+ levels are low, PTH stimulates osteoclasts and reduces urinary excretion of Ca2+ ions
- also stimulated the production of calcitriol, a kidney hormone that promotes intestinal absorption of calcium
which glands regulate bone density?
thyroid and parathyroids
how is the adrenal gland well placed?
well places to receive nerve input from splanchnic nerve and to recieve ACTH from the pituitary via the bloodstream
- well placed to have two ways to regulate metabolism
what are the histological layers of the adrenal gland?
Capsule
Zona glomerulosa
Zona fasiculata
Zona reticularis
Adrenal medulla
(will come up in exam along with functions)
what three layers of the adrenal gland make up the adrenal cortex?
the zona glomerulosa, zona fasiculata and the zona reticularis
what does the capsule of the adrenal gland do?
contains the gland
what does the zona glomerulosa so?
produces mineralocorticoids to regulate electrolyte composition
- aldosterone targets kidney to regulate ionic composition in urine by retaining Na+ ions and water, and losing potassium ions in the urine
what triggers aldosterone release?
- fall in sodium levels
- rise in potassium levels
- angiotensin II (blood pressure)
what does the zona fasiculata do?
ACTH from anterior pituitary stimulates glucocorticoid (cortisol and corticosterone) production from zona fasiculata
- down regulates the immune system (bc its energy expensive) and raise blood glucose levels through gluconeogenesis in the liver to make glucose available to major organs eg brain
