T1 L5 : Calcium Homeostasis Flashcards
what is calcium useful for
Exocytosis
Physical properties of bone
what does hypocalcaemia cause and why
in neurones ) (1m
It destabilises neurones and causes seizures
what are the physical signs of Hypocalcaemia
- Carpopedal spasm
2. Chvostek’s sign
what is Chvostek’s sign
when there is low plasma calcium causing an increase in the permeability of neuronal membranes to sodium
action potentials may be spontaneously generated, causing contraction of peripheral skeletal muscle.
what are the acute consequences of hypercalcaemia
Thirst & Polyuria
Abdominal Pain
what are the chronic consequences of hypercalcaemia
Constipation Musculoskeletal aches / weakness Neurobehavioral symptoms Renal calculi Osteoporosis
what are the relative % of how calcium is found in the blood
40% protein bound
10% bound to cations
50% ionised
when most only ionised calcium be measured directly
- if albumin conc is less than 20g/L
- If severe acute illness
what cells make the parathyroid hormone
Chief cells
how do chief cells sense the low calcium levels
Calcium sensing receptors
what is the process if there is less ca
sensing receptor formation is altered
Modified chief cell processes ( uses MG2+ for next stage )
PTH secretion
how does the PTH hormone work molecularly
PTH activates the PTH 1 recep
causing a change in its shape
where are PTH 1 receptors found
In the bone and the kidney
what is the rapid action of PTH
3m
it causes calcium release in bine via the osteocytic membrane pump- via activating osteoblasts which activate a RANK ligand
causing osteoclast prolif
Ca2+ released into the blood stream
what does PTH cause in the kidney
1-Rapid calcium reabsorption and a decrease in the reabsorption of PO4
2- Stimulates the production of vit D (25-oh-Vit D) from cholecalciferol, to 1,25 OH vitamin D (active form )
this causes calcium transporters & binding as well as Protein in gut cells
resulting in an increase in calcium absorption
