Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

physio > parathyroid > Flashcards

parathyroid Flashcards

1
Q

what is 1,25-(OH)2D3, (calcitriol )how is it formed.
- what is its function

A
  • a steroid hormone derivative of vitamin D3.
  • Formed with sunlight in the skin and subsequent processing in the liver and the kidney.
  • enhances intestinal ca absorption

,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is pth secreted by
- what is its function

A
  • peptide hormone secreted by the parathyroid gland
  • elevates blood ca levels by mobilizing ca from bone and increasing ca reabsorption in the kidney
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is calcitonin, what is it secreted by
- what is the funciton

A
  • a peptide hormone which is secreted by parafollicular cells of the thyroid
  • lowers ca levels
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is right regulation of ca critical for

A
  • cellular functions such as neuronal and muscular activation
  • normal growth and maintains of the skeletal system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the regulatory functions of intracellular ca

A
  • muscle contraction
  • neuronal excitability
  • secretion
  • metabolism
  • gene expression
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is ca in plasma and extracellular fluids important for

A
  • generation of intracellular ca signals
  • blood coagulation
  • cell-cell interactions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Calcium salts in bone and teeth are an essential structural component that yield: 2

A
  • stuructural integrity and strength
  • growth and morphogeneisis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the 2 ways in which intracellular ca can be increased

A
  • opening of ca channels on the cell membrane and release of ca from the sarcoplasmic reticulum
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is cytosolic free ca concentration at rest and in extracellular fluid

A
  • cytosolic = 0.1uM
  • blood 1-2mM
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the three basic fractions of ca in plasma

A
  • free ca = 50% improtant!!!
  • ca bound to extracellular proteins such as albumin = 1/2 of extracellular plasma
  • calcium complexed with other plasma ions and metabolites such as citrate and phosphate = 5-10%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

why is Ca binding proteins sensitive to pH

A

because the secondary carboxyl group binding sites have a pka in the physiological range and as the pH increases they become more fully deprotanated and ca binding affinity increases.
- conversely as the pH lowers binding affinity lowers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how does acidosis and alkalosis affect free ca

A

acidosis increases free calcium and alkalosis decreases free calcium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q
  • how can lowering ca lead to a excitatory affect on nerves and muscles
  • what is the syndrome calles
    ( hyperventilation)
A
  • during hyperventilation you are removing more Co2 = alkaline blood
  • less ca = more permeable Na causing excitation of neurons and muscles due to hyperexcitability
  • leads to tingling nerves and hypocalcemic tetany
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is effieceny of the absorption of ca in the gut

A

not very efficent most of it is eliminated via feces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the largest ca resvoir

A

bones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

where do the largest fluxes of ca occur

A

the largest fluxes of ca occur in the kidney through glomerular filtration but 98% of this is reabsorbed in the loop of henle and distal tubule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

how does phosphate absorption differ to ca absorption in the gut how is most of it excreted

A

more phosphate abosrption in the gut and most of it is excreted in through urine however the kidney recovers 80-90%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

where can we find the most phosphate? what is the interaction with plasma

A
  • in bone and also soft tissue and are in a rapid exchange equilibrium with plasma phosphate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the 3 types of cells involved in bone formation and resorption

A
  • Osteoblasts are the bone-forming
    cells that secrete the bone protein
    matrix (osteoid, primarily collagen) on
    which Ca2+ and PO 4 precipitate to
    form the rigid hydroxyapatite structure.

-Osteoclasts are responsible for bone
resorption and the mobilization of
bone calcium. They are large
multinucleate cells.

  • Osteocytes, the mature bone cells
    are enclosed within the bone matrix.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is osteocytic osteolysis

A

the rapid transfer of calcium from bone canaliculi to the external surface of the bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are the function of cancliculi

A

provide an interface between the interior surface of the bone and the extracellular fluid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is the predominant method of sustained calcium liberation from bone

A

resroption via osteoclasts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what do osteoclasts secrete that allow them to tunnel into the bone.
- what is liberated

A

collegenase, phosphotse, and lysozomal enzymes that create an acidic environment.
- as osteoclasts tunnel their way through bone calcium, phosphate, and amino acids are liberated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what procceses reverses prolonged hypocalcemia

A

resorption of bone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

how do osteolysis and resorption via osteoclasts differ

A
  • osteolysis extracts ca without loss of bone mass
  • resorption destroys the bone matrix and leads to loss of bone mass
26
Q

what occurs during bone remodeling

A

osteoblsts lay down new matrix and calcium and phosphate are mineralized

27
Q

what are the 3 principal organ targets for calcium regulation

A

gut,bone,kidney

28
Q

how is phopate uptake and release relate to ca

A

regulated coordinately with ca

29
Q

where are vitamin D and D3 synthesized

A

D- is ingested and formed in the skin with UV

D3 occurs in kertinocytes in the skin where 7-dehydrocholesterol is photo-converted to D3

30
Q

how is inactive vitamin D (inactive) converted to 1,25-(OH)2D3
- how many steps, what are the enzymes, what occurs?

A
  • 2 step proccess involving p450 hydroxylase in the kidnkey and liver
  • first hydrozylation occurs in the liver yielding 25 (oh)2D3
  • second occurs in the liver catalyzed by 1-alpha hydroxylase yielding 1-25(oh)2D3
  • 24,25 D3 is also synthesized in the other kidney but it is inactive and is a means for removing excess D3
31
Q

what is the primary site of 1,25(OH)2D3 regulation
- what stimulates the production and what inhibits it

A
  • the kidney through 1-alpha-hydroxylase
  • stimulated by PTH and low levels of Ca and ohisphate
  • inhibited by elevated lebvels of 1,25OHD3 which favors the formation of inactive 24,25 (OH)2D3
32
Q

what is the cellular action of 1,25(OH)D3
What is it bound to when circulating

A
  • when cicrculating bound to the globulin, transcalciferin (TC) with only a small amount circulating freely
    -the free form crosses the membrane where is targets vitamin D receptor
  • dimerization occurs with the retinoic acid receptor resulting in stimulation or inhibiition of gene expression
33
Q

what are all the major effects of 1-25OHD3 mediated by

A

steroid like nuclear receptors that regulate gene transcription

34
Q

was is the most important effect of 125OHD3
- what else does it cause the absorption of

A
  • to stimulate the absorption and active transport of calcium fromm the intestine through increased expresion of Ca binding proteins and Ca pumps
  • also stimulates the absorption of magnesium and phosphate
35
Q

how does 125OH2 D3 the effects of PTH
(2)

A
  • it enhances its affects on bone resorption theough recrutiment of osteoclasts
  • also acts on the parathyroid gland to reduce PTH synthesis
36
Q

how is 125OHD3 required for the normal mineralization of bone
- what disease is vitamin D deficency asscociated with

A
  • supplies ca and phosphate
  • rickets which causes weakness and and bowing of weight bearing bones
37
Q

what is the movemnt of Ca through the intestine and how does 125Oh2D3 increase this

A

-Ca enters microvilli at the brush boarder throughh channels
- Ca diffuses thorugh enterocyte facilitated by Calbindin
- Ca is activley transported across the basolateral membrane by Ca pumps and 125oh2D3 increases the expression of these channels, pumps, and binding proteins enhancing asorption

38
Q

what type of hormones is PTh and and what cell is it secreted by and in what gland

A

peptide hormone, chief cells, parathyroid gland

39
Q

what is the location of the parathyroid and what is its relationship with the thyroid

A

4 glands behind the thyroid but although they share circulation they dont have any functional interactions

40
Q

how is PTH inintally translated and what is it cleaved into
- where is it stored

A
  • as a pre-prohormone
  • cleavage of leader and pro sequences yield biologivally active peptide which is stored in secretory granueles
  • further cleavage may occur in the gland or periphery to yield 34aa active Nterminal fragemnt with a inactive Cterminal fragment
41
Q

how is PTH releasr controled

A
  • under the control of plasma Ca through a receptor
42
Q

half life of PTH

A

10 min

43
Q

how is PTH secretion regulated by Ca sensing receptor

A
  • at high plasma Ca CaR is activated to turn on PLC and increase IP3 which inhibits PTH secretion
  • it also inhibits AC to decrease cAMP
  • at low plasma ca Ca R isint activated and AC inhibition is relieved which increases cAMP whcih stimulates PTH
44
Q

what is the primary regulator of PTH secretion and what is the relationship
- when is pth secretion maximal and minimal

A
  • free calcium is the primary regulator
  • PTH secretion is inversely related to ca
  • pth is maximal when ca falls below 1.2mM and minimal when ca increases above 1.3mM thus pth is contorlled in a realy narrow range
45
Q
  • how does 125OhD3 regulate pth
  • how do histamine, dopamine, and epinephrine effect pth
A
  • inhibits it
  • stimulae cAMP in the chief cells
46
Q

what is the mechanism of PTH on target cells

A
  • PTH binds to activate GPCR to stimulate AC and increase cAMP. which activates fiunctions on bones and kidneys
47
Q

what is the effect of PTH on ocsteoclasts

A
  • its indirect and is mediated by receptors on oseobalsts that secrete RANKL that then activate osteoclasts by binding to RANK
48
Q

what do osteoblasts secrete that sequesters RANKL

A

osteoprotegerin OPG

49
Q

how does estrogen effect PTH

A

opposes its effect by surpressing RANKL and increasing OPG

50
Q

what are the effects of PTH on bone

A
  • PTH stiumulates osteolysis that transports ca out of canalicular fluid
  • stimulates bone resorption by osteoclasts liberating ca and phosphate and causing bone destruction
51
Q

what is the effect of PTH on the kidney

A
  • increases calcium reabsorption in the sidstal tubule
  • inhibits phosphate eabsorption stimulating phosphate excretion
  • stimulates the synthesis of 125ohd3
52
Q

what type of hormone is calcitonin and what cells is it secreted by and by what gland

A
  • peptide hormone secreted by parafollicular cells of the thyroid gland
53
Q

what is the effect of calcitonin
- how does it compare to pth hand 125ohd3 in maintaing calcium homeostasis
- what is it stimulated by

A
  • decreases plasma ca
  • less critical
  • stimulated by high ca
54
Q

what is the affect of calcitonin on pth, bone, and kidney

A
  • antagonizes pth by inhibiting osteoclast mediated bone resorption
  • in it increases the reabsorption of cal and phosphorus leading to increased urinary excretion of these ions
55
Q

what is osteoperosis and why are postmenopausal women more succesptable
- why do those in space have it

A
  • prolonged osteoclast activity over osteoblast activity
  • common is menopause bc estrogen deficency. Estrogen surpesses RANKL and so estrogen defiecny increases osteoclasts
  • inactivity / low gravity
56
Q

what is primary hyperparathyroidism
-what other pathology can it cause

A
  • excess PTH secretion leading to hypercalcemia caused by a benign parathyroid neoplasm that secretes PTH
  • may lead to kidney stones
57
Q

secondary hyperparathyroidsm

A
  • results from hypocalcemia which can occur from renal disease and vitamin D defiency (rickets). Low calcium causes hypertrophy of the PT gland
58
Q

what is primary hypoparathyroidism what other disease can it lead to

A
  • casued by inadverant removal of the parathyroid glands during thyroid surgury
  • can also be caused by autoimune damage to the PT gland
  • can cause hypocalcemic tetany
59
Q
A
60
Q
A

physio (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions