Calcium Homeostasis Flashcards
What are the 5 roles of calcium in the body?
Signalling - exocytosis of synaptic vesicles in the body Blood clotting Apoptosis Skeletal strength Membrane excitability
What is the consequence of hypocalcaemia?
Increase the neuronal sodium permeability increasing excitation and can cause tetany
What is the outcome of hypercalcaemia?
Decrease neuronal sodium permeability and decrease neuromuslcar activity leading to cardiac arrhythmias
What 3 compartments of the body is calcium stored within?
The extracellular matrix of the bones -99%
Intracellular fluid -0.9%
The extracellular fluid 0.1%
How is calcium stored within the bones?
As hydroxyapatite crystals
What element other than calcium does hydroxyapatite contain and why is this important?
Phosphorus, important role in calcium homeostasis because without it calcium cannot be laid down in the bones
What is the calcium contained within in the ICF?
Mitochondria and sarcoplasmic reticulum
What percentage overall is free calcium?
0.05% and this is all that is physiologically active
In what state is calcium in the extracellular fluid?
40% bound to carrier proteins
50% free, ionised and physiologically active
10% are bound to plasma anions forming complexes
What two protein carriers hold calcium?
Albumin - 80%
Globulin - 20%
What increases the binding capacity of calcium to carrier proteins
An increased pH, alkaline environments
When would we be able to create an alkaline environment in the body?
Hyperventilation
What acts as a reservoir for plasma calcium?
Bones
What cells form bone?
Osteoblasts
What cells degrade bone?
Osteoclasts
