ICPP S3 Calcium Homeostasis

Question 1

How much calcium does the body contained and where is 99% of it found?

Answer 1

~1kg and in the bones

Question 2

What are blood serum calcium levels?

Answer 2

1.9-2.3mM

Question 3

How is calcium homeostasis regulated at a whole body level?

Answer 3

Intestinal Ca2+ uptake
Ca2+ reabsorption in the kidneys
Bone calcium regulation

Question 4

How are whole body homeostatic mechanisms to control [Ca2+] under homeostatic control?

Answer 4

Ca2+ receptors sense parathyroid hormone, this is released in response to hypocalcemia

1,25dihydroxyvitamin D3 promotes absorption of Ca2+ in GI tract

Calcitonin - acts to increase [Ca2+]

Question 5

What are the extracellular, cytoplasmic and sarcoplasmic concentrations of calcium?

Answer 5

Extracellular = 1x10^-3M

Cytosolic = 1 x 10^-7M

Sarcoplasmic = 2-3 x 10^-4M

Question 6

Name some processes controlled by Ca.

Answer 6

Muscle contraction
NT release
Fertilisation
Apoptosis and necrosis
Metabolism regulation
Learning and memory

Question 7

How are Ca2+ concentrations maintained?

Answer 7

Relative impermeability of the plasma membrane to Ca2+.

Pumps and transporters that move Ca2+ out of the cell.

Ca2+ buffer proteins that bind to Ca2+ - reducing concentration of free Ca2+

Question 8

What are the ATP dependant mechanisms for maintaining Ca2+ gradients?

Answer 8

Ca2+ ATPases: PMCA and SERCA

Transporter mechanisms: NCX - moves Ca2+ out by moving Na+ in.

Question 9

What are some mechanisms that increase Intracellular [Ca2+]?

Answer 9

Influx CSM through VOCCs and LGICs

Effluxfrom ER and SR through activation of CICR receptors aka ryanodine receptors
IP3 receptors through IP3R gated channels.