Calcium And Phosphate

Question 1

Describe calcium homeostasis

Answer 1

Regulated by PTH and vitamin D

1. Increase calcium reabsorption from bone
2. PTH works on kidney, increases bone reabsorption
3. Regulates production of active form of vitamin D

Question 2

Describe the phosphate regulation

Answer 2

Na/PO4 co-transporter in PCT. PTH inhibits this transporter, PO4 is not reabsorbed and excreted in the urine. FGF 23 also inhibits this co transporter …

Question 3

Describe the process of PTH secretion

Answer 3

Parathyroid cells has calcium sensitive channel, when high Ca in extracellular fluid, the calcium binds to receptor leading to inhibition of PTH secretion. The opposite happens when calcium is low = PTH secreted.

Question 4

Describe the role of Vitamin D homeostasis

Answer 4

Vitamin D in diet is inactive, or sunlight, so produces D3 in liver. PTH stimulates the enzyme renal 1-alpha hydroxylase to convert D3 into calcitrol. Happens in kidneys, this forms calcium absorption from gut, maintenance in bone - negative feedback on PTH

Question 5

Describe hypercalcaemia and hypocalcaemia

Answer 5

Hyper calcaemia: calcium blocks Na influx, so less membrane excitability.

Hypocalcaemia: enables greater Na influx so more membrane excitability. Causes parasethesia, convulsions, arrythmias, tetany. Signs: choose terms sign

So much more

Question 6

So many more

Answer 6

So many more. Revise this lecture