schmidt

Question 1

Role of Calcium

Answer 1

• required for enzyme activities: directly (citric acid cycle, glycogen degradation) and Indirectly (calmodulin)
• mediates hormone responses as second messenger
• essential for blood coagulation
• essential for muscle contraction
• required for stability of bone (mineralization, hydroxylapatite)

Question 2

Ca++ pools

Answer 2

• in serum, about 50% of Ca+ is free and 50% is bound to protein or small molecules

Question 3

describe calicum and phosphate relationship

Answer 3

• calcium and phosphate are regulated INVERSELY
• Mobilization of bone calcium (to increase serum Ca+) is accompanied by increase in phosphate excretion
• high phosphate intake leads to increased Ca2+ excretion

Question 4

hormones of Ca+ metabolism

Answer 4

• Calcitriol = stimulates Ca+ uptake in the gut
• Parathyroid hormone (PTH) = stimulates resorption of bone Ca+ into the serum and also stimulates synthesis of calcitriol in the kidney
• Calcitionin (CT) = stimultes Ca+ exretion by the kidney

Question 5

what occurs in low serum caclium

Answer 5

• release of Calcitriol and Parathryroid hormone
• -> Calcitriol –> increases gut absorption of Ca –> increase serum Ca
• -> PTH –> increases serum calcium via bone and inhibits Ca excretion

Question 6

what occurs in high serum calcium

Answer 6

• Calcitonin –> increase excretion of Ca+ in the kidneys and causes bone to reabsorb ca+

Question 7

describe the source of calcitonin and PTH

Answer 7

• PTH = syntheiszed in the chief cells of the parathryoid gland
• calcitonin is synthesized in the thyroid gland

Question 8

describe the actions of PTH on cells in the kidney

Answer 8

• increase resopriton of Ca+ in the distal tubule, the collecting ducts and the ascending limb of the loop of henle
• stimulates phosphate excretion
• stimulates the synthesis of calcitriol

Question 9

describe the actions of PTH on cells in the bone

Answer 9

• stimulates the resorption of Ca2+ by osteoclasts

Question 10

actions of calcitonin

Answer 10

• AIM AT LOWERING THE SERUM CALCIUM CONC
• Act through G-protein coupled receptors (cAMP levels)
• IN BONE –> INHIBIT RESORPTION OF Ca++
• IN KIDNEY –> STIMULATE Ca+ EXCRETION

Question 11

describe the source of calcitriol

Answer 11

• synthesized from cholesterol
• water-INSOLUBLE STEROID
• calcitriol synthesis involved skin, liver and kidney

Question 12

describe the action of calcitriol

Answer 12

• enters cells and bind to a nuclear receptor (nVDR)
• can also bind to non-classical membrane receptors
• TARTET ORGANS = INTESTINE, BONE, KIDNEY
• STIMULATE TRANSCRIPTION OF:
• -> Ca2+ binding proteins
• -> Ca2+ ATPase
• -> facilitators of vesicle formation

Question 13

hypercalcemia vs hypocalcemia

Answer 13

HYPERCALCEMIA
–> formation of kidney stones, degradation of the skeletal (bones and moans)
HYPOCALCEMIA
–> neurological impairment, CV collapse, hypotension, and dysrhythmias

Question 14

define ricketts (osteomalacia)

Answer 14

• results from LOW vitamin D levels or INSUFFICIENT Ca2+ intake
• -> osteoid matrix and cartilage are formed, but not mineralized
• -> leads to soft, pliable bones

Question 15

defien osteoporosis

Answer 15

• multifactorial and largely unknown cause

- loss of bone mineral

Question 16

define renal osteodystrophy

Answer 16

• kidney disease leads to Ca2+ loss in urine –> insufficient calcitriol production