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Calcium Homeostasis
Chapter 6 - A & P Lecture
| Question | Answer |
|---|---|
| where is calcium primarily stored in the body? | within bone |
| what detemines the level of calcium in the blood? | movement of calciuminto or out of bone |
| when does calcium enter and leave bone? | enters when osteoblasts create new bone(deposition), & exists when osteoclasts break down bone (resorption) |
| what are the roles of calcium in the body? | stimulation of skeletal muscle contraction, stimulation and regulation of cardiac muscle contraction, exocytosis of cellular molecules |
| which 3 hormones control blood calcium levels? | parathyroid hormone (PTH), calcitriol (active vitamin D3), calcitonin |
| where is PTH secreted from? | cells in parathyroid gland |
| what stimulates the release of PTH? | reduction in blood calcium levels |
| what are the direct effects of PTH? | increase blood calcium by stimulating bone breakdonwn and enhancing calcium reabsorption in the kidneys |
| what is the indirect effect of PTH? | promotes activation of calcitriol which increases calcium absorption in small intestine |
| what is RANKL? | a regulatory cytokine molecule found in membrane bound and soluble forms on osteoclasts and osteoblasts |
| what does the soluble form of RANKL do? | triggers osteoclast formation |
| how does RANKL activate osteoclasts? | RANKL binds to its receptor (RANK) on precursor cells activating them into mature osteoclasts and stimulating bone resorption |
| how does PTH affect RANKL? | PTH stimulates osteoblasts and osteocytes to osynthesize and secrete RANKL, increasing blood calcium levels |
| what is calcitriol and what does it do? | active form of vitamin D3 that increases blood calcium by stimulating intestinal absorption of calcium |
| what is calcitonin and what does it do? | lowers blood calcium levels by inhibiting osteoclast activity |
| what is osteoporosis? | a condition characterized by porous bones and loss of bone matrix |
| what are the effects of osteoporosis? | loss of bone mass weakens bones, making them more easily deformed and fractured |
| why is osteoporosis more common in women? | 2.5 times more likely due to decreased reproductive hormones, inadequate calcium intake, and no weight bearing exercise |
| how can early diagnosis help with osteoporosis? | early diagnosis allows for preventative treatment |
| what are 4 classes of medications used to treat osteoporosis? | bisphosphonates, estrogen like medications, antibiotics, calcitonin replacement |
| how does aging affect bone matrix? | bone matrix decreases, becoming more brittle due to less collagen and reduced hydroxyapatite |
| hwo does aging affect bone mass? | bone mass decreases; spongy bone is lost first, followed by compact bone |
| what skeletal changes occur with aging? | increased fractures, bone deformity, loss of height, pain and stiffness, stooped posture, loss of teeth, wear of articular cartilage leading to arthritis |
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