Introduction to Ca2 homeostasis W4 Flashcards
What do we mean by Ca homeostasis
About keeping the level of Ca at a constant level in the extracellular compartment (plasmas and extra cellular fluid)
2.5mM of total Ca and half of that is free Ca (1.25mM)
3 hormones that control these levels
– Parathyroid hormone (PTH) (key player)
– Calcitonin
– Vitamin D
What are the consequences of too little or too much Ca
Major consequence of change in extra cellular Ca is teh changes to excitability of excitable cells (neurones/muscle cells)
If Ca changes then it changes how these cell types are going to function
How does Ca change the excitability of excitable cells
Ca is important in controlling the memb permeability and specifically in controlling the perm to Na
Low extra cell Ca = increases Na permeability
High extra cell Ca = decreases Na permeability
Increased Na perm =
> Na in cell = > + charge into the cell = Depolarisation
Decreased Na perm =
Less Na into cell = - charge = Hyperpolarisation
Too little Ca outside cell and consequences
Hypocalcemia
Will increase nerve and muscle excitability as there is depolarisation and closer to the threshold
Potentially dates l as can cause spasms of resp muscles in diaphragm
Too much Ca outside cell and consequences
Hypercalcemia
Decreases nerve/ muscle excitability b erasure of hyperpolarisation
Can result in cardiac arrhythmias
99% of Ca is where
In bones and teeth
