calcium homeostasis and hypocalcemia

Question 1

what is the most abundant cation in the body?

Answer 1

Calcium (Ca2+)
- important for many intracellular reactions

Question 2

list examples of intracellular reactions that require Calcium

Answer 2

• muscle contractions
• nerve cell activity
• activation of enzymes
• release of hormones through exocytosis
• blood coagulation
• cell membrane stability

Question 3

calcium homeostasis is __________ and __________

Answer 3

• tightly controlled
• adjustments made within 5% of normal

Question 4

where else in the body is Calcium important?

Answer 4

maintaining the structureal integrity of the teeth and bones (less acute)

Question 5

what is the function of phosphate?

Answer 5

• binds calcium, reducing the available free calcium
• as blood calcium levels rise, blood phosphate levels fall (inversely related)
• phosphate concentrations are controlled by the same systems that control blood calcium concentrations

Question 6

where are the 3 pools of calcium?

Answer 6

• bone
• intracellular calcium
• extracellular fluid

Question 7

discuss how calcium is stored in the bone?

Answer 7

99% of all calcium is stored as hydroxyapatite crystals
- also contains phosphate

Question 8

discuss how calcium is stored in intracellular calcium?

Answer 8

bound to proteins or contained in mitochondria

Question 9

discuss how calcium is stored in the extracellular fluid?

Answer 9

• interstitial calcium
• blood calcium
• 0.5% of bone calcium pool (amorphous crystals in solution)

soluble bone calcium pool allows access to the large reserve of calcium in bone