Test 3: lecture 10 Flashcards
functions of calcium
Contraction of muscles
Blood coagulation
Enzyme activity (as a second messenger)
Neural excitability
Hypocalcemia causes nervous system excitation and muscle____
tetany
Hypercalcemia ____ nervous system and muscle activity
depresses
___ provides the tensile strength to bones
Organic matrix of bone (30%)
- Collagen fibers
- Tensile strength
___ provides the compressional strength of bones
Crystalline salts of bone (70%)
- Hydroxyapatite Ca10(PO4)6(OH)2
- Compressional strength
what inhibits the formation of hydroxyapatite?
high levels of PPi (pyrophosphate)
formed by PC-1 (plasma cell membrane glycoprotein 1 )(non bone tissues)
how to form hydroxyapatite
PPi (TNAP) → hydroxyapatite
if bones don’t have TNAP they will form soft bones (uncalcified)
TNAP = tissue non-specific alkaline phosphatase (bone)
remodeling of bones is done by
osteoblasts- make new bone
osteoclasts- breakdown and resorb bone
GH stimulates osteoblasts
Fracture stimulates osteoblasts
New organic matrix (___) maintains the bone strength.
collagen fiber
regulation of calcium metabolism is by ___
Vitamin D
Parathyroid hormone (PTH)
Calcitonin (Thyroid C cells)
that target the: GI, kidneys and bone
how to form vit D
1-25 (OH)2D3 is the active form of Vit D made in the kidney
Cholecalciferol (D3) can be stored in the ___ for months
liver
effects of 1,25(OH)2D3
____ Ca2+ and PO43- intestinal absorption
Increase renal ____ absorption
Promote bone ____ (small quantities)
Increase bone ____ (extreme quantities)
increases
Ca2+ and PO43-
calcification
resorption
how does vit D work in intestine
stimulates the production of calcium binding proteins → promotes calcium absorption
types of cells in the parathyroid gland
chief cells → make PTH
oxyphil cells → increase amount with age (old chief cells?)
how to make PTH
peptide hormone
has a precursor (pre-proparathyroid hormone) with a signal peptide that is cleaved (pro-parathyroid), then another part is cleaved (parathyroid hormone)
rapid phase of PTH:
Rapid phase of absorption: PTH activates calcium pump to pump Ca2+ and PO43- into ECF.