Calcium Homeostasis Flashcards
What is the role of calcium in the body?
Blood clotting Apoptosis Skeletal strength Membrane excitability Signalling
What is the effect of hypocalcaemia?
Increases neuronal Na+ permeability, hyper excitation of neurons
What is the effect of hypercalcaemia?
Decreases neuronal Na+ permeability, reduce excitability and depress neuromuscular activity
Where is calcium mostly distributed in the body?
Bones
In what form is calcium stored in the body?
Hydroxyapatite
What is calcium bound to in the blood?
Albumin
Globulin
What type of conditions is binding capacity of calcium increased?
Alkalotic conditions
What is the function of osteoblasts?
Bone building cells which lay down a collagen extracellular matrix which they then calcify
What is the function of osteocytes?
Regulate the activity of osteoblasts and osteoclasts
What is the function of osteoclasts?
Mobilize the bone, secrete H+ ions to dissolve calcium salts
Provide proteolytic enzymes to digest the extracellular matrix
What hormones increase [Ca2+] plasma?
Parathyroid hormone
Calcitriol
How many parathyroid glands are there?
4
How does parathyroid hormone increase [Ca2+]plasma?
Stimulate osteoclasts to increase reabsorption of Ca2+ and phosphate in bone
Inhibits osteoblasts to reduce Ca2+ deposition in bone
Increase reabsorption of Ca2+ from kidneys
Increases renal excretion of phosphate
Stimulates kidneys to synthesise calcitriol
What is calcitriol derived from?
Vitamin D
Where can vitamin D be found in diet?
Fatty fish (mackerel, tuna)
Fish liver oils
Egg yolks
