Brainscape's Knowledge GenomeTM

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


See full index

ENI 2 > physiology of calcium regulation > Flashcards

physiology of calcium regulation Flashcards

1
Q

where is the majority of the calcium stored

A
  • within the bone as extracellular matrix
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

total calcium of blood consists of:

A
  • 40% bound to plasma proteins
  • 10% in compexes
  • 50% in an ionized form
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how is blood calcium levels maintained

A
  • buffering (exchangebale clacium in bone salts and in mitochondria)
  • hormonal control
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what hormones control calcium

A
  • parathyroid hormone (PTH)
  • calcitonin
  • active vitamin D3 (calcitriol)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

where is PTH produced and by what

A

external and internal parathyroid glands by the principle cells (chief cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

where is calcitonin produced

A

parafollicular cells of thyroid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

where is calcitriol activated

A

kidney

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how is calcium homeostasis maintained

A
  • if hypocalcemic and need more calcium: increase PTH and produce more activated vitamin D3
  • if hypercalcemic and need less clacium: decrease PTH
  • in severe hypercalcemia: calcitonin

continuous secretion of PTH allows for increase or decrease depending on needs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what stimulates parathyroid hormone

A

hypocalcemia
- acts to raise blood calcium level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what kind of receptor mediates PTH

A

G-protein couple calcium sensing receptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

discuss PTH synthesis

A
  • preprohormone
  • prohormone (amino acids cleaved)
  • into secretry vesicles as PTH (more amino acids cleaved)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

where is PTH degraded

A

liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

discuss PTH secretion

A
  • PTH secreted continuously but increases a extracellular fluid iCa level decreases
  • direct negative feedback system
  • membrane receptors on principal cells
  • receptor coupled G protein which controls exocytosis of PTH containing vesicles
  • PTH secreted at moderate rate at normal range of iCa
  • PTH secretion increases when iCa falls and decreases when it increases
  • very responsive system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the actions of PTH within the body

A
  • bone (fast) gets calcium from bone fluid
  • bone (slow) phase gets calcium from bone
  • kidney: reabsorption within tubules recovers more calcium from urinary filtrate
  • intestine: indirect effect through the actiation of vitamin D to get calcium from gut
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what tissues does PTH interact with

A
  • bone
  • kidney
  • intestine
17
Q

describe the fast phase of calcium turnover from bone

A
  • begins in minutes and progressively increases for hours
  • PTH acts on existing osteocytes and osteoblasts
  • cells connected by long filmy processes that extend through the bone called osteocytic-osteoblastic membrane system contain fluid within themselves and the bone = bone fluid
  • increased calcium uptake from bone fluid
18
Q

discuss how PTH interacts with bone fluid to increase calcium

A
  • PTH interacts with membrane receptors on osteocytes and osteoblasts
  • increases permeability to calcium on bone fluid side of membrane
  • increased calcium uptake from bone fluid takes Ca out of bone via ATP powered pump
  • bone fluid calcium level drops
  • nearby calcium phosphate crystals replace calcium in the bone fluid (osteolysis)
19
Q

discuss the slow phase of gaining calcium from bone

A
  • activation of osteoclasts
  • no receptors for PTH on osteoclasts so signal comes from activated osteocytes and osteoblasts
  • existing osteoclasts are activated (stage 1)
  • new osteoclasts are formed (stage 2)
  • progressive depletion of bone mineral
  • takes 48 hours to respon
  • gets phosphate as well
20
Q

discuss how bone resorption releases calcium

A
  • multinucleated osteocasts attach to bone
  • formation of reaction chamber at attachment = creation f resorption cavity
  • bone resorption by release of organic acids and proteolytic enzymes
  • released Ca and P transported across osteoclast to blood
21
Q

discuss the interaction between PTH and the kidney

A
  • increases calcium reabosrption in the late distal tubules and collecting tubules
  • results in retention of Ca and Mg
  • decreases phosphorus reabsorption in the renal proximal tubule
  • results in rapid loss of phosphorus
  • important as PTH gets Ca from bone but also P so needs to find a way to get rid of P as P will effect availibility of Ca
22
Q

discuss the interaction between PTH and vitamin D

A
  • get vitamin D from skin or diet
  • first conversion from vitamin D to 25-hydroxyvitamin D in liver
  • final conversion to active vitamin D (calcitriol) occurs in the renal tubules
  • catalyzed by the enzyme 1 alpha hydroxylase (25 hydroxyvitamin D becomes 1,25 dihydroxyvitamin D
  • enzyme is activated by PTH
  • rise in PTH = increase in calcitriol
23
Q

relate PTH to vitamin D activation

A

PTH activates vitamin D in the renal tubules through 1-alpha-hydroxylations when blood phosphorus levels are low

24
Q

discuss the importance of calcitriol for calcium regulation

A
  • increases calcium absorption from the intestine
  • decreases calcium excretion by the kidneys
  • needed for normal functioning of bone
  • increases the active transport of calcium
  • enters intestinal epithelial cells and increases the synthesis of calcium-transport proteins
  • effects renal tubular epithelial cells to increase calcium reabsorption from urine
  • essential for bone reabsorption in response to PTH and deposition of bone
25
Q

how does active vitamin D work

A
  • through calcium channel proteins in lumen of intestine
  • calcium binding protein (calbindin)
  • calcium ATPase pumps (basolateral)
26
Q

is calcitonin clincially significant

A

usually no - has an overall weaker influence than PTH

27
Q

what stimulates calcitonin

A

hypercalcemia

28
Q

what secretes calcitonin

A

parafollicular cells

29
Q

what are the effects of calcitonin

A
  • fast phase bone response (inhibits osteoclast absorptive activities)
  • slow phase bone response (reduce formation of new osteoclasts)
  • slight (insignificant) effects on the kidney and intestinal tract
30
Q

is magnesium hormonally controlled

A

no

ENI 2 (81 decks)

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