Calcium Homeostasis Dr. Bo Liu 2024

what is the normal serum calcium range?

8.8-10mg/dl

describe how insulin is secreted? draw 5 marks

Increase blood glucose. this triggers the beta cells to move glucose into the cell. mitochondria breakdown glucose(Kreb cycle) and release ATP. this causes the closer of the ATP sensitive K+ channel, resulting in depolarization. this causes voltage gated calcium channels to open, causing calcium influx. this causes granules containing insulin to be release through exocytosis.

what are normal fasting glucose levels?

below 5.5 mmols

what cells in the parathyroid gland produce parathyroid

cheif cells

what is the function of the parathyroid hormone?

increase blood calcium

describe the negative feedback mechanism which regulates PTH release

increase in extracellular calcium is detected by calcium sensing receptors in cheif cell. this inhibits adenycl cyclase which decrease cAMP which inhibit PTH exocytosis.

how does PTH increase calcium in the blood.

increases cAMP which causes ca2+ in the kidney, small intestine and bones to be released.

how is ca2+ released via PTH from the bones?

PTH stimulates the osteoclasts and inhibits osteoblast to increase bone resorption and increase calcium in the blood

how is ca2+ released via PTH from the kidneys?

increase in phosphate excretion, resulting in less phosphate calcium complex so more calcium is available to be reabsorbed.

how is ca2+ released via PTH from the small intestines?

increases the reabsoprtion of ca2+ by activating vitamin d as this is needed to reabsorb calcium from the small intestines

where in the body is vitamin d activated?

the kidneys

what is the active form of vitamin d

calcitriol vitamin d3

how does activated vitamin d increase the reabsorption of ca2+ in the gut?

binds to nuclear recptors which sit on response elements that increase the expression of calcium transport proteins which increases calcium reabsoprtion.

where is calcitonin synthesised?

parafollicular cells in the thyroid gland

what is the physiological response to hypocalcimia?

PTH is secreted, which caused bone resorption, increases calcium and phosphate absorption from small intestines, and increase in phosphate excretion and decrease in calcium excretion, increase in vitamin d3 formation

what can happen as a result of hypocalcemia?

tetanic muscle contraction, seizures, cardiac effect, brittle nails, osteoporosis

what can cause increase levels of PTH? PTH disorder

adenoma or hyperplasia which secretes PTH leading to chronically elevated calcium and low phosphate