B6-060 Thyroid Gland Physiology (used Ninja Nerd instead of awful lecture) Flashcards
synthesis of thyroid hormone begins when the paraventricular nuclei in the hypothalmus secrete […]
tryrotrophin-releasing hormone (TRH)
TRH travels through the vascular connection between the hypothalmus and anterior pituitary, called the [….]
hypophyseal portal system
TRH stimulates pituitary to secrete […] into the blood stream
thyroid stimulating hormone (TSH)
TSH binds to the receptors on the follicles of the thyroid and stimulate it to produce […]
thyroglobulin (basic unit of thyroid hormone)
[…] needs to be ingested to produce thyroid hormone
iodide
how is iodide brought from the lumen into the thyrocyte?
via Na/I symport
enzyme in the luminal space that performs iodine oxidation, iodination, and coupling
thyroid peroxidase
3 functions of thyroid peroxidase
- iodine oxidation
- iodination
- coupling
converts iodide to iodine
iodine oxidation (thyroid peroxidase)
process that attaches one or two iodine molecules to thyroglobulin to create MIT or DIT
iodination (thyroid peroxidase)
couples the iodinated tyrosine amino acids into T3 and T4
coupling (thyroid oxidase)
DIT+DIT= T4
DIT+MIT= T3
T3 and T4 are collectively known as
thyroid hormone
once iodinated, the thyroglobulin enters the thyrocyte via
pinocytosis –> vesicles
the vesicles containing thyroglobulin fuse with lysosomes, resulting in
isolated T3 and T4
**vesicles containing isolated T3 and T4 fuse with the membrane and are released into the bloodstream
in the blood, T3 and T4 bind to the transport protein […]
thyroxine binding globulin (TBG)
TBG is synthesized by the
liver
summarize the steps of thyroid hormone synthesis
.
what is the structural unit of the thyroid gland?
follicles
what hormone is produced by the anterior pituitary gland?
TSH
which cells are stimulated by TRH?
follicular cells (thyrocytes)
what does TSH activate?
Gs protein
what is the main amino acid of thyroglobulin?
tyrosine
what is added to thyroidglobulin during iodation?
Iodine
what binds TH in the bloodstream?
TBG
enzyme that removes iodine from thyroxine
5’ deiodinase
enzyme that converts T4 to T3 (active)
5’ deiodinase
enzyme that converts T4 reverse T3 (inactive)
5-deiodinase
T3 and retinoic acid bind to the transcription factor to move into the nucleus and stimulate synthesis of
NaKATPase
**leading to production of more sodium-potassium pumps, requiring more energy=catabolic state
TH effects on liver [3]
glycogenolysis
gluconeogenesis
increase LDL receptors
**increases blood glucose level and uptake of bad cholesterol
effects of TH on heart
stimulates beta 1 receptors to increase contractility, SV, and BP
effects of TH on CNS
increases dendrite formation
increases myelination
increases number of synapses
**as a result, hyperparathyroidism can cause irritability
TH regulates bone […]
remodeling
cells responsible for bone deposition
osteoblasts
cells responsible for bone resorption
osteoclasts
how does TH affect chondrocytes in the epiphyseal plates?
stimulates proliferation, hypertrophy, and ossification
**causes bones to lengthen
TH stimulates endochondral
ossification
TH effects on adipose
stimulates lipolysis
**excess glycerol converted to glucose, increases blood glucose
TH regulates both catabolism and anabolism.
Hyperthyroidism causes the balance to shift to […]
catabolism
how does hyperthyroidism effect muscles?
catabolism causes weak, atrophied muscles/movements
how does TH affect the skin?
increased body temperature causes vessels to dilate it to try to cool –> skin flushed, radiates heat
increases sweat production
brittle nails, thin hair [hypo or hyperthyroidism]
hypothyroidism
thick hair [hypo or hyperthyroidism]
hyperthyroidism
how does TH affect the GI system?
stimulates secretion and enhances motility
diarrhea [hypo or hyperthyroidism]
hyperthyroidism
constipation [hypo or hyperthyroidism]
hypothyroidism
what substance is required for T3 to exert its effects?
retinoic acid
T3 [increases or decreases] the available ATP in the cell
decreases
**NaKATPases constantly using ATP
irritability [hypo or hyperthyroidism]
hyperthyroidism
paraventricular neurons in the hypothalmus release
thyrotropin releasing hormone (TRH)
TRH goes through the […] to the pituitary
hypophyseal portal system
TRH stimulates anterior pituitary to release
TSH
TH is transported through the blood via
TBG
high levels of TH exert a negative feedback mechanism that
inhibits paraventricular nucleus from making TRH
-decreases TSH production
-decreases T3 and T4 production
low levels of TH exert a negative feedback mechanism that
stimulate the paraventricular nucleus to release excessive TRH
-increases TSH production
-increases T3 and T4 production
TH increases the basal metabolic rate by
increasing the number of NaKATPases
TH aims to increase blood glucose by stimulating [3]
lipolysis
glycolysis
gluconeogenesis