#33 Flashcards
(26 cards)
Where is the thyroid gland located?
above the trachea and below the larynx
Thyroid stimulating hormone
targets thyroid gland
stimulates secretion of thyroid hormones and growth of thyroid gland
regulation: stimulated by TRH, inhibited by thyroid hormones
mechanism of thyroid hormone synthesis
TG is iodized (3 times on T3, 4 on T4), in colloid cell
TSH binds to G protein, Pka stimulates endocytosis into follicular cells, T3/4 are released into the bloodstream
difference between t3/t4
t4 has four iodines t3 has 3. t4 eventually becomes t3
what happens if iodine is not in diet?
hypothyroidism
WHich thyroid gland is most acive?
T3. Its mostly secreted as T4 but is turned into T3 in the tissues
actions of thyroid hormone
increases metabolic rate and heat production, by enhancing sympathetic activity
stimulates protein synthesis and growth through increased gene expression, stimulation of growth hormone
purpose of t4
negative feedback on hypothalamus
hypothyroidism
caused by thyroid gland failure, deficiency in TRH or TSH, iodine deficiency, autoimmune disease
cretinism
hypothyroidism in infants and young children
low metabolic rate, growth retardation, mental deficits, hypothermia
myxedema (hypothyroidism in adults)
Low BMR weight gain cold sensitivity dry rough skin scanty hair sluggish mental activity puffy eyes and lips
why does goiter happen?
no iodide, so thyroid hormone can’t be synthesized. This means T4 can’t put negative feedback, so TSH stimulation increases and makes the thyroid huge
causes of hyperthyroidism
Thyroid stimulating immunoglobins bind to TSH receptor and stimulate the thyroid
autoimmune production of TSH or TRH, thyroid tumor
graves disease
Thyroid stimulating immunoglobins bind to the TSH receptor and stimulate the thyroid
high metabolic rate, poor heat tolerance, weakness, low body weight, bulging eyes, goiter
adrenal cortex secretes
steroids
adrenal medulla secretes
cattecholamines, release contolled by sympathetic NS
Medulla made of modified post ganglionic sympathetic neurons
epinephrine effects
increases free fatty acids, blood glucose, conversion of glycogen to lactate in muscle, and glucagon secretion.
Pheochromocytotoma
adrenal tumor causing a heightened sympathetic state (high bp, tachycardia, pain, constipation, rage) triggered by physical exertion, anxiety, and bowel movements
Three categories of corticosteroids
Mineralocorticoids (aldosterone)
Glucocorticoids (cortisol)
Sex hormones (DHEA)
cortisol general actions
increase blood glucose, protein degradation, lipolysis,
cortisol secretion regulation
stimulated by corticotropin releasing hormone from hypothalamus and adrenocorticotropic hormone from AP
circadian rhythm causes cortisol fluctuations throughout day
long term cortisol exposure
increases appetite and promotes lipogenesis and fat deposition. Promotes glucose liberation
short term stress symptoms
increased heart rate, blood pressure, bronchiole dilation
glycogen breakdown, blood flow to muscles, metabolic rate increases
long term stress response
kidneys retain sodium and water, blood volume and pressure rise, proteins and fats converted to glucose, blood glucose increases, suppressed immune system
