What type of regulation is calcium
humoral regulation
where is calcium stored in the body
bones
what are some general functions of calcium
bone structure, nerve function, blood clotting, muscle contractions, cellular metabolism
What are the three methods of Ca control?
1) PTH when Ca is low
2)calcitriol (vitamin D)
3)calcitonin secreted from parafollicular C cells in thyroid when Ca is high
What are the two types of cells in the parathyroid gland
chief cells and oxyphil cells
what do chief cells do
produce PTH
what kind of hormone is PTH
small protein hormone
what is the main goal of PTH. How does it do this?
elevate Ca2+ concentration
1)stimulate bone resorption
2)increase kidney Ca2+ reabsorption
3)decrease renal phosphate reabsorption
4)stimulate Vit D activation in kidneys
how does vit D affect Ca2+
increases efficiency of Ca2+ reabsorption in the small intestine
Where and how is external Ca2+ [ ] sensed
sensed by calcium sensing receptors (CaSR) on chief cells
Describe the formation of Vit D
1) DHC is converted to pre-vitamin D using UV rays
2)pre-vitamin D is converted to Vitamin D cholecalciferol in the skin (not active)
3)25-hydroxylase converts vit D (inactive) to 25-hydroxyvitaminD in liver
4)moves through circulation to kidney where 1a-hydroxylase converts it to 1,25-dihydroxyvitamin D (active form)
What stimulates 1a-hydroxylase
PTH
is vitamin D a vitamin
no, it’s a secosteroid (simlar to steroid) and is transported via Vitamin D binding protein in blood
What is the main function of vitamin D and what does it inhibit(- feedback)
maintains normal blood levels of calcium and phosphorus (promotes bone mineralization) and maintains immune function and prevents excessive inflammation, negatively feeds back to inhibit PTH
What is vitamin D (active) called
1,25(OH)2D or calcitriol
what does vitamin D do in the intestine
increases calcium and phosphorus absorption
what does vitamin d do in bones
mobilizes calcium stores
Where do we get vitamin D (active) from other than from the normal way
diet (mild, oj, salmon, supplements)
What kind of vitamin D is found in supplements
vitamin D cholecalciferol
what do osteoblasts and osteoclasts do
osteoblasts build bone, osteoclasts break it down
two hormones act on osteoblasts and they eventually become osteoclasts. how does this happen?
PTH and Vitamin D act on osteoblasts which then become preosteoclasts which differentiate into osteoclasts to break down bone
how do osteoclasts increase their surface area and why is it important?
ruffled membrane allows for more release of enzymes to eat away at bone
What cells are inside the bone
osteocytes
What causes osteoperosis
hyperactivity of osteoclasts
