Endocrine Control of TH Flashcards
follicular cells
- serve as extracellular storage site for thyroid hormones
- produce:
- Tetraiodothyonine (T4 or thyroxine)
- Tri-iodothyronine (T3)
- Tetraiodothyonine (T4 or thyroxine)
T3 and T4 are derived from
amimo acid tyrosine
T3 and T4 contain
iodine
C cells function
secrete calcitonin
how do you make thyroid hormones
tyrosine and idodine
where do the steps of synthesis of thyroid hormones occur
thyroglobin molecules within the colloid
tyrosine containing thyroglobin is exported from the follicular cells into the colloid by
exocytosis
how does the capture idondine from the blood
iodine pump
where are thyroid hormones stored
colloid
- usually stores enough to supply the bodies neeeds fro several months
how are thyroid hormones secreted
phagocytize thryroglobin laden colloid
- frees T3 and T4 and therefore can diffuse across the plasma membrane into the blood
what is the main function of TH
determinate of basal metabolic rate
other functions of TH
- influences synthesis and degration of carbohydrates, fats, and proteins
- increases target cell responsiveness to catecholamines
- increases heart rate and force of contractions
- essential of normal growth
- critical role in normal development of the nervous system
thyroid hormone _______ body metabolic rate
increases
thyroid hormones are an important regulator of
oxygen, energy consumption, energy expendatures
Th influences both the_________ of CHO, fats and proteins
synthesis and degration
small amoutn of Th effect on glucose
converts glucose to glycogen
(hypersecretion) large amount of TH effect on glucose
converts glycogen to glucose
TH produces action similar to sympathetic NS called the
sympathomimetic effect
sympathomimetic effect
- increases target cells responsiveness to catecholamines
- “permissive actions” by causing both the proliferation of specific cathecolamines target receptos on target tissues such as the heart
thyroid hormones effects on the cardivascular system
- increases hearts responsiveness to cathecholamines
- increases heart rate and force (increases cardiac output)
- peripheral vasodilator (dissipates extra heat generated during calorigenic effects
- increases blood flow and volume
Th effect on Growth and NS
- increased GH secretion (stimulates GH and promotes IGF-1’s action in protein synthesis and skeletal growth)
- regulates normal development of the NS
TH deficency in children effect
stunted growth and CNS disorders
Negative Feedback
(-) stress. (+) cold in infants
hypothalamus
thyrotropin-releasing hormone (TRH)
anterior pituitary
TSH
thyroid gland
Thyroid hormone (T3+T4)
hypothyroidism causes
- fails to produce TH
- deficency in TRH or TSH
- inadequate dietary supply of iodine
