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Flashcards in Ca metabolism Deck (66)
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1

Is there a circadian rhytms for thyroid hormone

We have confirmed that in humans there is a circadian rhythm of TSH with a peak level occurring at around 02:40 h and levels remaining above the mesor from 20:20–08:20 h

2

How regulation of calcium with PTH/D3 occurs

3

Regulation of calcium via calcitonin

4

Do we know the role of calcitonin

No, uncertain

5

What are remedies for rickets

Fish liver oil

Sun exposure

UV-irradiation of certain foods

6

Roles of Ca

  • v Major structural component of the skeleton
  •  Blood clotting (cross-linking of fibrin)
  •  Regulation of enzyme activities (induction of conformational changes or co-factor)
  •  “Second messenger” of hormones signals .Release from endoplasmic reticulum
  •  Membrane excitability

v Secretion of hormone/neurotransmitters
v Action potential

  •  Muscle contraction

v Triggered by the release of Ca++ from the
sarcoplasmic reticulum.

7

Where the most Ca is found and how extracellular Ca can be regulated

Extracellular and
Intracellular Ca++
levels are tightly
regulated

Skeleton 99%

8

Disequilibrium between bound and unbound 
Ca++ causes ___

tetany

9

what is alkalosis

Hyperventilation
reduces the partial
pressure of CO2. Less
H2CO3 is produced and
H+ falls → alkalosis

10

How hyperventilation and tetany are connected

v Hyperventilation
reduces the partial
pressure of CO2. Less
H2CO3 is produced and
H+ falls → alkalosis
v To compensate H+ is
released from serum
proteins. The negatively
charged protein binds
Ca++

Reduction in free serum Ca++ → tetany (spasm of skeletal muscle)
v similarly, blood transfusions in which citrate is the anti-coagulant can
cause tetany (due to Citrate chelating Ca++)

11

How many thyroid glands are there

4

Can be 5 th in 15% of people

12

What cells produce PTH and when PTH is release

v Chief cells (and oxyphil cells)
produce Parathyroid Hormone
(PTH)
v PTH is released in response to
low levels of ionized Ca in ECF

13

Calcitonin action

Reduces serum Ca

14

Half life for PTH, how it is cleaved

v Highly conserved
v Short half-life
v 2-4 min
v Cleaved into two
fragments (amino and
carboxy terminus)

15

How chief cells react on Ca concentration in the blood 

calcium sensing receptor (CaR) located on Chief
cell membrane of chief cells detect ECF Ca++

16

Ca receptros are ___ receptros and couple with

Ca receptors on the parathyroid
cells
vSeven-transmembrane domain
receptor
v Coupled with G-protein complex
vHighly conserved

17

What happens to parathyroid cells with Ca concentration alteration

v Concentration- dependent
conformation alteration


vHigh Ca concentrations –
Decreased cAMP and increased IP3
vLow Ca concentrations – Increased
cAMP and decreased IP3

18

v PTH functions to
regulate calcium
levels via its actions
on three target
organs___

– the bone,
kidney, and gut.

19

How PTH influences bones

PTH increases the
resorption of bone
by stimulating
osteoclasts and
promotes the
release of calcium
and phosphate into
the circulation.

20

Mineral content of bones

v 99% of total Ca+2
v 90% of total PO4-3
v 50% of total Mg+2

21

Cells in bone

v Osteoprogenitor cells
v Osteoblasts
v Osteocytes
v Osteoclasts

22

Organic matrix of bone: composition 

v Collagen (90-95%)
v Proteoglycans
v Glycoproteins
v Lipids

23

Osteobalsts function

v1mg of osteocalcin
binds 17 mg of
hydroxyapatite
vSerum level is indicator
of bone growth.

24

Osteonectin function

vBinds collagen and
hydroxyapatite
vMay serve as nucleator
for calcium deposition
in the bone.

25

structure of bone

26

Describe osteoblast differentiation

27

Bone formation process describe 

28

Turn-over Ca2+ in bone is ___per year in
infants and 18% in adults

100%

29

Bone remodelling is performed by

Carried out by bone modeling units:
osteoclasts dissolve bone followed by
osteoblasts that lay down new bone

30

Factors regulating remodeling

Mechanical factors
v Hormonal factors induced by PTH
v Paracrine factors (i.e. IGF-II produced by
osteoblasts) may act on neighboring
osteoblasts and osteoclasts