Bone and Calcium Flashcards
Where is calcium in the blood?
50% albumin bound
40% ionised
10% complex bound with phosphate/citrate
What is the difference in calcium location during an acid state compared to an alkalotic state?
Acidotic - less albumin bound calcium as replaced by H+ and more ionised
Alkalotic: more albumin bound and less ionised
What can alkalosis do to calcium?
Hypocalcaemia as blowing off lots of CO2
lips tingle
What is the role of calcium?
Circulating molecules INSIDE cells
stabilises sodium pumps sitting wihin channels to prevent activity
What happens during hypocalcaemia?
Uncontrolled nerve firing = cardiac arrhythmias/cardiac arrest
Where is the location of phosphate?
85% mineralised in bone
Serum phosphate
In structural/informational/effector molecules
How much calcium is in bone?
99%
What is the role of the parathyroid glands?
Secrete parathyroid hormone when low calcium via chief cells
Cause increase in extracellular calcium
How do the parathyroid increase EC calcium?
- bone: increase osteoclast activity = bone reabsorption = less calcium and phosphate release
- kidney: increases calcium reabsorption, decreases phosphate reabsorption
- intestines: increased hydroxylation of vitamin D. to produce calcitriol which promotes calcium reabsorption through gut by stimulating calcium binding proteins
How does phosphate change calcium concentrations?
Forms salts with calcium so decreases ionised mounts
What do high levels of calcium do to PTH?
- inhibit PTH
- not fully suppressed (basal amount secreted)
- slight secretion decrease not major
What do low levels of calcium do to PTH?
- lack of calcium picked up by calcium sensing receptor
- dramatic increase in PTH secretion
What is the role of the calcium sensing receptor?
- reduces PTH secretion
- increases PTH breakdown
- suppresses PTH gene transcription
How does familial hypocalciruic hypercalcemia occur?
- inactivate calcium sensing receptors o PT cannot sense if high and PTH not suppressed
- high serum calcium means more reabsorbed and less in urine
What other factors affect PTH secretion?
- increased by phsophate
- decreased by activated vitamin D
Where does PTH act on in the kidney?
D.C.T
upregulates channels
Where does calcium reabsorption take place?-
- DCT: PTH acts here
- PCT: paracellular, voltage gradient drives it
- LOH: paracellular, voltage gated driven, loop diuretics inhibit
What does calcium consist of in the bone?
hydroxyapatite
What is the bone made up of?
Collagen
Hydoxyapatite
What is bone made up of when it gets mineralised?
Calcium, phosphate, alkaline phospahtase
What do oesteoblasts do?
Contain and produce RANKL
PTH stimulate its production
What is RANKL
Stimulated by PTH
What do osteoclasts do?
RANKL receptors
- when activated form seal over bone and cause breakdown of RANKL releasing calcium
How do you intake vitamin D?
Absorb by diet or UV light
