Unit 2 - Calcium Flashcards
What are the main physiologic functions of Ca?
muscle contraction, hormone and neurotransmitter release, second messenger, coagulation, structural component of bone
What processes in the gut contribute to levels of Ca in plasma?
calcium is absorbed in the GI tract from the diet into the plasma
What processes in the bone contribute to levels of Ca in plasma?
Ca is sent to the bone for storage and accretion
What processes in the kidney contribute to levels of Ca in plasma?
Ca is sent to the kidney to be filtered and then can be reabsorbed back into the plasma if needed
What hormones contribute to the regulation of calcium homeostasis?
PTH (parathormone), vitamin D, and calcitonin
What hormones increase plasma levels of Ca?
PTH and Vitamin D
What hormone decreases plasma levels of Ca?
calcitonin
What is the chemical nature of parathormone?
it is a protein
What is parathormone secreted by?
chief cells of the parathyroid gland
What is the secretion of parathormone triggered by and what is the trigger sensed by?
a decrease in serum ionized Ca which is detected by calcium-sensing receptors in the membranes of chief cells
What does parathormone stimulate?
osteoclasts to begin bone resorption to increase plasma Ca, increase renal vitamin D activation, increase renal Ca resortion and decrease renal PO4 reabsorption
How is vitamin D synthesized (3 steps)?
- Vitamin D can either come from food, or UV light turns cholesterol into vitamin D3 (cholecalciferol)
- Vitamin D3 is synthesized into 25(OH)D3 in the liver and then is sent to the kidney
- PTH stimulates the synthesis of 1,25(OH)2D3 from 25(OH)D3
What is the main of Vitamin D?
increase Ca and PO4 intestinal absorption
What are secondary functions of vitamin D?
increase Ca and PO4 renal reabsorption and increase bone resorption
What is the chemical nature of calcitonin?
32 amino acid peptide
What is calcitonin secreted by?
the thyroid gland
What is calcitonin secreted in response to?
hypercalcemia
What triggers calcitonin secretion?
high plasma calcium and gastrin
What are the main functions of calcitonin?
decrease of Ca intestinal absorption, resporption from bone, renal reabsorption
What are the common causes of hypercalcemia?
primary hyperparathyroidism and vitamin D toxicosis
Generally, what is a main sign of hypercalcemia?
decreased neuromuscular excitability
What are the treatments for hypercalcemia?
volume expansion, loop diuretics
What are the common causes of hypocalcemia?
primary hypoparathyroidism and renal failure
Generally, what is a main sign of hypocalcemia?
increased neuromuscular excitability
What are the treatments for hypocalcemia?
IV calcium gluconate, oral calcium, vitamin D
Why does calcium affect neuromusclular excitability?
because the role of calcium is to block sodium channels, the amount of it depends on the effect it will have
How does low levels of calcium effect depolarization?
it makes it easier
How does high levels of calcium effect depolarization?
it makes it harder
