Lecture 18 - Endocrine System 2 Flashcards
2 lateral lobes connected by median mass called an isthmus
Thyroid gland
The thyroid gland is composed of follicles that produce the glycoprotein ___________________.
Thyroglobulin
Colloid (thyroglobulin + iodine) fills lumen of follicles and is a precursor of _________________.
Thyroid hormone
Parafollicular cells produce the hormone _________________.
Calcitonin
Thyroid hormone is actually 2 related compounds, which are _______ and _________.
T4 (thyroxine)
T3 (triiodothyronine)
_______ has 2 tyrosine molecules + 4 bound iodine atoms.
T4
_______ has 2 tyrosine molecules + 3 bound iodine atoms.
T3
________________ affects virtually every cell in the body; it is the #1 metabolic hormone in the body
Thyroid hormone
True or false: Thyroid hormone increases metabolic rate and heat production (calorigenic effect). It also regulates tissue growth and development, and maintains blood pressure.
True
The thyroid gland stores TH ___________________.
Extracellularly
________________ is necessary for the synthesis of thyroid hormone.
Iodine
________ and ________ are transported by thyroxine-binding globulins (TBGs).
T4; T3
Both T4 and T3 bind to target receptors, but _____ is 10 times more active than _____.
T3; T4
True or false: Peripheral tissues convert T4 to T3.
True
Rising TH levels provide negative feedback inhibition on release of __________.
TSH
Hypothalamic thyrotropin-releasing hormone can overcome __________________ during pregnancy or exposure to cold (non-human).
Negative feedback
___________________ of TH in adults is myxedema; goiter if due to lack of iodine.
Hyposecretion
Thyroid swells to maximize surface area to attempt to absorb any trace of iodine present
Goiter
True or false: Hyposecretion of TH in infants is cretinism.
True
Hypersecretion of TH is ________________ (constant increased metabolism causes patient’s inability to keep weight on)
Graves’ disease
___________________ has no known physiological role in humans
Calcitonin
Calcitonin is antagonist to _______________
PTH
At higher than normal doses, calcitonin ______________ osteoclast activity and release of calcium form bone matrix
*Osteoclasts break down bone
Inhibits
4 to 8 tiny glands embedded in posterior aspect of thyroid
Parathyroid glands
True or false: Parathyroid glands contain oxyphil cells (function unknown) and parathyroid cells that secrete parathyroid hormone (PTH).
True
PTH is most important in __________________ (by releasing calcium from bone).
Calcium homeostasis
PTH stimulates _______________ to digest bone matrix and release calcium to blood.
Osteoclasts
PTH enhances reabsorption of ____________ and secretion of phosphate by kidneys.
Calcium
PTH promotes activation of _______________ (by kidneys); increases absorption of calcium by intestinal mucosa.
Vitamin D
Negative feedback control: rising calcium in blood ____________ PTH release
Inhibits
_________________ due to tumor:
- -> bones soften and deform
- -> elevated calcium depresses nervous system and contributes to formation of kidney stones
Hyperparathyroidism
Hypoparathyroidism following gland trauma or removal or dietary Mg deficiency:
- -> not enough ______ in bloodstream
- -> results in tetany, respiratory paralysis, and death
Calcium
Paired, pyramid-shaped organs atop kidneys
Adrenal glands
Adrenal glands are structurally and functionally 2 glands in one. Name these 2 glands.
Adrenal medulla
Adrenal cortex
Nervous tissue; part of sympathetic nervous system
Adrenal medulla
3 layers of glandular tissue that synthesize and secrete corticosteroids
Adrenal cortex
3 layers of adrenal cortex
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
Superficial layer that produces mineralocorticoids (hormones that help control balance of minerals and water in the blood)
Zona glomerulosa
Middle layer that mainly produces the metabolic hormones (glucocorticoids)
Zona fasciculata
The innermost layer that produces small amounts of adrenal sex hormones (gonadocorticoids)
Zona reticularis
Regulate electrolytes (primarily sodium and potassium) in ECF
Mineralocorticoids
Mineralocorticoids are necessary for proper _____________ function.
Nervous system
Affects ECF volume, blood volume, blood pressure, levels of other ions
Importance of sodium
Sets resting membrane potential of cells
Importance of potassium
Most potent mineralocorticoid
Aldosterone
True or false: Aldosterone stimulates sodium reabsorption and water retention by kidneys; elimination of potassium
True
________________ release is triggered by decreasing blood volume and blood pressure, and rising blood levels of potassium
Aldosterone
Hypersecretion due to adrenal tumors
- -> hypertension and edema due to excessive sodium
- -> excretion of potassium leading to abnormal function of neurons and muscle
Aldosteronism
Keep blood glucose levels relatively constant
Glucocorticoids
Glucocorticoids maintain blood pressure by increasing action of _________________.
Vasoconstrictors
_____________ is the only glucocorticoid present in significant amounts in humans; stress hormone
Cortisol
