PSL300H1 Lecture 4: Calcium Balance
Document Summary
Happens at 3 target sites (will increase or decrease absorption/secretion/excretion of ca2+): Total body ca2+ = intracellular + extracellular (ecf/plasma + bone) 3 cells in bone responsible for formation and maintenance of bone: Osteocytes: maintain bone. (these are previously osteoblasts that are completely surrounded by bone matrix -> Therefore just maintain bone in its immediately vicinity) Making bone = creating calcium phosphate complexes (calcium crystallization) Calcium turnover/year: 100% in infants, 18% in adults. Osteoclasts break down bone via acid and enzymes. Bone dynamics (~100 days): osteoclasts resorb, osteoblasts form, osteocytes (retired osteoblasts) Rank = receptor activator of nuclear factor kappa b. Osteoprotegerin (opg) secreted by osteoblasts blocks rankl/rank interaction. Released from the parathyroid glands (chief cells) - 4 in total. Function: increases plasma ca2+ concentration -> 3 ways! Parathyroid cells are exquisitely sensitive to changes in extracellular calcium concentration. Ca2+-sensing receptor on plasma membrane used to monitor extracellular ca2+: When ca2+ binds to the receptor (i. e. high [ca2+]):
