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PHYSIOLOGY II > Lecture 15: Calcium Balance > Flashcards

Lecture 15: Calcium Balance Flashcards

1
Q

T/F Ca is the most abundant element in the body

A

true

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2
Q

~99% of body Ca is found where

A

skeletal bone and teeth
0.9% is cytoplasmic (soft tissue)
0.1% in blood and exctracellular fluid (10mg/dl)

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3
Q

what is the second most abundant mineral in the body

A

Phosphate

0.1% in blood and ECF

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4
Q

hydroxyapatite

A

biological apatite that makes bone (Ca+Phosphate)

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5
Q

how can plasma ionized Ca be altered?

A
  • increases in plasma proteins increases total bound Ca w/ minimal changes to ionized Ca
  • increases in anions (phosphate) increase anion or complexed Ca and decrease ionized Ca
  • acid base fluxes: protons compete w/ calcium for albumin binding sites
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6
Q

how can plasma ionized Ca be altered?

A
  • hormonally mediated exchange b/w intestine, bone, kidney
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7
Q

Ca+ balance in the body (b/w ECF/bone/intestine/kidney) is slow compared to Ca+ balance in the

A

ECF (B/w ECF + bone fluid)

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8
Q

Ca and phosphate levels in the blood are regulated by ______ and vitamin _____

A

Parathyroid Hormone (PTH) and Vit D

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9
Q

calcitonin opposes …..

A

PTH

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10
Q

What conditions stimulate PTH

A
  • low plasma Ca
  • high plasma phosphate
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11
Q

what is the main regulator of Ca metabolism

A

PTH

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12
Q

what conditions stimulate Vit D and what does it do

A
  • low plasma Ca
  • increases absorption of Ca from the inteestine
  • mainly balances Ca metabolsim via absorption in the gut
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13
Q

______ is not essential for the homeostasis or balance of Ca but does correct symptoms of hypercalcemia

A

Calcitonin
stimulates bone resorption of Ca

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14
Q

most domestic animals have how many pair of parathyroid glands

A

4

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15
Q

what is the plasma half life of PTH

A

2-5 min

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16
Q

PTH is a _____ hormone

A

peptide

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17
Q

high Ca levels inhibit the release of ….

A

PTH

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18
Q

majority cell type in the Parathyroid gland, they detect extra cellular Ca levels

A

Chief cells

*HUMORAL RESPONSE

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19
Q

bone is a living tissue composed of mineral components called the ______

A

matrix

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20
Q

osteoblasts

A

bone builders
deposite the matrix

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21
Q

osteocytes

A

former osteoblasts that are now internalized in the bone

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22
Q

osteoclasts

A

bone demolition
resorb the matrix
they are dervied from modified macrophages

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23
Q

what are the 2 calcium pools

A

Labile pool:in bone fluid, allows for rapid exchange of Ca w/ blood
Stable pool: in bone matrix, allows for storage and slow exchange of Ca, site of bone resorption

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24
Q

bone organization

A

osteon w/ central canal
lamellae canaliculi

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25
Q

the osteoblast-osteocyte network is a pool of living tissue that has a ______ reserve of Ca+

A

labile

26
Q

PTH activates membrane bound _____ in the osteobalsts and osteocytes to take in Ca

A

Ca pumps
* Ca then transferred from these cells to the central cancal and into the blood
* phosphate left behind

27
Q

PTH receptors are located in….?

A

osteoblasts

NOT osteoclasts

28
Q

In fast exchange, Ca is moved from the _____ pool in the bone fluid into the ____ by PTH-activated Ca+ pumps located inside the osteocytic-osteoblastic membrane

A

labile pool into the plasma

29
Q

In slow exchange, Ca is moved from the _____ pool in the mineralized bone into the _____ through PTH induced dissolution of the bone by ______

A

stable pool to the plasma, osteoclasts

30
Q

PTH inhibits the bone formation activity of _______

A

osteoblasts

31
Q

Long term slow exchange of Ca+ causes a _______ in osteoblast activity and a ________ in osteoclast activity

A

decreased osteobalst activity
increased osteoclast activity

32
Q

osteoblasts release _______ (a ligand) that binds its receptor to cause macrophages to differentiate into osteoclasts

A

RANKL (binds to RANK)

33
Q

Osteoclasts release ______ and _____ to dissolved the matrix and release Ca and phoshpate

A

Hcl and hydrolytic enzymes

34
Q

what are the 2 direct effects of PTH in the kidney

A
  • Conserves Calcium
  • Eliminates Phosphate
35
Q

how do the kidneys conserve calcium when stimulated by PTH

A
  • resorb more filtered Ca
  • increase Na/Ca cotransport in the DT
  • urine Ca decreases
36
Q

how do the kidneys eliminate phosphate

A
  • phosphate resobsorption decreases
  • inhibits Na/PO43- cotransport in the PCT
  • urine phosphate increases
    ** Phosphate elimination is necessary to avoid cation-anion complexes and apatite formation in blood**
37
Q

how does PTH activate Vit D

A

by stimulating 1α hydroxylase within the kidney, which converts vit D precursor into its active form

38
Q

how is Vit D obtained

A

through diet or dervied from precursor in skin w/ UV light exposure

39
Q

what are the 3 steps of VIT D synthesis

A
  1. UV dependent proteolysis of 7-dehydrocholesterol to vitamin D3 (Can also come from diet)
  2. Activation : in liver, CYP27A1 adds OH group to carbon 25
  3. PTH dependent activation: in kidney, CYP27B1 adds OH group to Carbon 1
40
Q

effects of Vit D in the kidney

A

promotes Ca reabsorption form the DT and promotes PT resorption of phosphate

41
Q

in bone, Vit D synergizes w/ PTH to stimulate ________ and bone remodeling

A

resorption

42
Q

osteomalacia in adult animals

A
  • impaired ability to absorb Ca and Phosphate in the intestine
  • usually results from interstinal surgery that causes decreased Vit D absorption
  • malabsorption syndrome, malnutrition, renal failure, celiac disease
  • bones become demineralized and soft, fracture easily
43
Q

Phosphate is regulated directly by _____ in the intestines

A

vit D

44
Q

Phosphate is regulated indirectly by….

A

the inverse relationship bw plasma phosphate and Ca
* a fall in phosphate increases Ca, resulting in decreased PTH
* PTH decrease increases renal phosphate reabsorption

45
Q

calcitonin is produced in _____ cells of the thyroid gland

A

Parafollicular C cells

46
Q

hypercalcemia stimulates calcitonin release to decrease_________

A

ECF Ca
* this decreases bone resportion by limiting the activity of osteoclasts via the cAMP pathway
* inhibits Ca and phosphate reabsorption in kidney

47
Q

calcitonin has no effects in the intestine or on ________

A

vit D

48
Q

malignant cell clusters secrete _______ and bind to the PTH receptor

A

PTH-related peptide (PTH-r)
an antagnosit to the PTH receptor

49
Q

what is the effect of PTH-rp bindng to PTH receptor

A
  • increases bone resorption
  • increases renal Ca reabsorption
  • inhibits renal phosphate reabsorption
    ** most common cause of hypercalcemia and dogs and is common in cats**
50
Q

2 main effects of excessive PTH-rp secretion

A
  • hypercalcemia
  • hypophosphatemia
51
Q

clinical signs of hypercalcemia

A
  • weakness, lethargy, difficulting getting up
  • hyporexia, nausea, V+, constipation
  • hypertension, arrythmia
  • polydipsia, polyuria, urolithiasis, UTIs
52
Q

the main effects of Vit D occur where

A

small intestine
* increases Ca and phosphate absorption by increasing the expression of Ca binding protein, Calbindin

53
Q

Rickets in juveniles

A

insufficient Vit D, Ca and phosphate to mineralize bone
* growth failure, skeletal abnormalities

54
Q

primary hyperparathyroidism results in excess _______, and subsequently _______ and _______

A

PTH
- hypercalcemia
- hypophosphatemia

55
Q

physiological effects of PTH Hypersecretion

A
  • elevated urine levels of PO43- and Ca
  • increase in ca-containing kidney stone
  • impaired renal functioning
  • reduces the excitability of muscle and nerves
  • thinning of bone, increased risk for fracture
  • osteoporosis, osteomalacia

commonly caused by PTH-secreting parathyroid adenoma

56
Q

horses lack _______ and thus don’t form calcitriol

A

1α-hydroxylase

57
Q

for horses, intstinal absorption of Ca is ________ of Vit D signaling

A

independent
they absorb more Ca in the GI tract than any other species

58
Q

main mechanism of removing excess dietary calcium (equine)

A

renal excretion

59
Q

equine chronic failure may be indicated by ________ due to decreased excretion

A

hypercalcemia
neoplasia, hyperparathyroidism and Vit D toxicity may also cause hypercalcemia

60
Q

What causes equine hypervitaminosis D

A

latrogenic (Dr caused) or by ingetion of calcinogenic plants
* hypercalcemia
* hyperphosphatemia

61
Q

physiological symptoms of hypoparathyroidism

A
  • low PTH
  • hypocalcemia
  • hyperphosphatemia
  • increased neuromuscular excitability
  • cataracts
  • cognitive changes
62
Q

what might cause hypoparathyroidsim

A
  • damage from surgical thyroidectomies
  • treatment for cancers
  • Grave’s disdease

PHYSIOLOGY II (17 decks)

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