Term
where is most of the body's Ca located?
of the free Ca, what are three locations?
and of those which ones can diffuse through capillary walls? |
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Definition
99 % is minerilized in bone
40% bound to plasma proteins (non-diffusible)
10% bound to ECF ions (is diffusible)
50% ionized (is diffusible thru capillary walls) |
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Term
the Ca concentration in the ECF is a balance of what 3 components?
where does rapid exchange of Ca occur?
what about slower exchange? |
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Definition
balance between GI intake/bone resorption & excretion through kidneys
rapid - between Kidney & non-mineralized Ca
slower - between ECF & mineralized bone |
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Term
where is most of our Phosphate stored?
in what form is the ECF P mostly?
what form of P is involved in exchange?
what is phosphate used for in the body?
what 2 organs are mainly involved in P balance? |
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Definition
85% in bone
Inorganic P mainly in ECF in form of HPO42-
PO43- this form is also used for energy metabolism & growth (structural component of bone)
kidneys & bone |
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Term
where is PTH synthesized?
what stimulates its release?
what's counter intuitive about PTH excretion?
what type of signal stimulates PTH release? |
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Definition
chief cells of the parathyroid gland
low Ca levels stim its release
in this case Ca actually inhibits hormone release (via a PLC/Ca signal)
a cAMP/Mg stimulates PTH release
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Term
what's the main to functions of PTH?
in what three ways is Ca concentration increased?
what type of signaling path does PTH initiate on a cell?
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Definition
PTH - increase Ca, decrease P
Bone - rapid osteocytic effect
longer osteoclastic effect (via paracrine signaling from osteoblasts)
Kidney - resorption of Ca (rapid)
GI tract - Ca absorption via VitD
signaling path is via Gs/cAMP |
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Term
where is calcitonin (CT) made?
what stimulates CT release?
what's CT's main physiological role?
what is this effect acted out on?
what can override the effects of CT? |
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Definition
parafollicular cells of the thyroid gland
plasma [Ca]
CT lower's Ca during times of hypercalcemia
effect on bone: shuts down osteoclasts & inhibit osteoclast formation
CT can be overridden by PTH |
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Term
1. how is VitD synthesized (pathway?
2. what's the inert form vs. active form?
3. what stimulates / inhibits it?
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Definition
1. precursor gets hit by sunlight to become VitD
in the liver it gets hydroxylated
in the kidney it get hydroxylated again
2. active form - carbon 1 is hydroxylated
inactive form - carbon 24 is hydroxylated
3. PTH promotes synthesis
PO4 & the active form in abundance inhibit it
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Term
effector sites for active VitD 1,25(OH)2D3
long term & rapid effects of VitD?
what's the permissive effect of VitD? |
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Definition
major site: intestinal mucosa
longterm: it increases expression of Ca binding protein to absorb more Ca
rapid: stimulate osteoblasts to promote mineralization
VitD is needed for bone resorption in response to PTH |
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Term
| what two effects does for example, a drop in plasma PO43 have? |
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Definition
inhibit PTH release (forces kidney to take up more phosphate)
stimulate activation of VitD (induce GI tract to absorb more phosphate)
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Term
| how are the gonadal hormones (estrogen & androgen) involved in mineral metabolism? |
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Definition
| directly involved in pubertal growth & closure of the epiphyseal plate & in Ca balance |
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Term
how are glucocorticoids involved in mineral metabolism?
what adverse effect does an excess have?
what's this syndrome called? |
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Definition
they're needed for normal skeletal growth via permissive actions on growth & metabolism
in excess (Cushing's syndrome) glucocorticoids effect all target organs involved in Calcium homeostasis |
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Term
what effect do thyroid hormones have on mineral metabolism?
what effect does hyperthyroidism have? |
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Definition
they're needed for normal skeletal development & Ca balance
hyperthyroidism can disturb Ca balance |
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Term
| what effect does growth hormone have on mineral metabolism? |
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Definition
| it directly effects bone growth, influence bone, kidney & gut |
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Term
what effects does hypoparathyroidism have?
symptoms? |
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Definition
decreased Ca & increased Phosphates
symptoms: increased neuromuscular excitability (tetany, CNS dysfunction)
muscle spasms/cramps,
cardiac arythmia
fragile bones
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Term
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Definition
increased PTH -> hypercalcemia & hypophosphatemia
symptoms:
neuromuscular impairment (weakness, CNS dysfunction)
polyuria & neprholithiasis (kidney stones)
long-term skeletal damage (demineralization) |
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Term
VitD deficiency
main cause
symptoms |
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Definition
result from dietary absence / lack of sunlight or renal / liver disease
symptoms:
severe bone demineralization
skeletal deformities & fractures
dental abnormalities
children - rickets
adults - osteomalacia |
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Term
1. osteoperosis
2. osteopetrosis
3. osteogenisis imperfecta |
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Definition
1. decr osteoblast / incr osteoclast activity
2. decr osteoclast activity (thick bones)
3. deficient collagen (weakened bones) |
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