What are functions of calcium?
- Bone, tooth structure
- Mineral store
- Action potentials in cardiac muscle
- 2nd messenger (muscle: excitation-contraction coupling)
How is calcium homeostasis achieved?
- Parathyroid hormone (When Low Ca2+)
- Calcitonin (When High Ca2+)
- Vitamin D
PTH & Calcitonin have exact opposite functions when regulating calcium levels
How does parathyroid hormone work?
- Secreted from parathyroid glands when low plasma [Ca2+]
Calcium increased by:
- Increased resorption of bone (osteoclasts)
- Increased Ca2+ reabsorption in kidney
- Increased Ca2+ uptake from intestines
Exact opposite to Calcitonin
How does Caltionin work?
- Secreted from thyroid glands when high plasma [Ca2+]
Calcium lowered by:
- Increased formation of bone (osteoblasts)
- Decreased Ca2+ reabsorption in kidney
Exact opposite to PTH
What are some hormones INCREASING bone formation and mass?
- Calcitonin
- GH
- IGF-1 (Insulin like growth factor)
- Insulin
- Oestrogen
- Testosterone
What are some hormones DECREASING bone formation and mass?
- Cortisol
- Parathyroid hormone
- Thyroid hormones
What are the 3 bone cells and what is each of their functions?
- Osteoblasts;
Synthesise and secrete bone ECM - Osteocytes;
Bone cell - an osteoblast which becomes embedded in bone matrix - Osteoclasts;
Large mutinucleated cells, derived from macrophages (phagocytes) that resorb & breakdown bone
What is hypo and hyper calcaemia?
Hypocalcemia - Reduced Ca2+
Hypercalcemia - Raised Ca2+
What is vitamin D deficiency and what the the consequences?
- Dietary deficiency
- Failure to synthesise in body
- Decreased calcium uptake from GI tract -> undermineralised bone, lacks rigidity
What is rickets and who does it occur in?
- Weak, soft bones, skeletal deformities
- As a result of Vit D deficiency
- Occurs in children
What is osteomalacia and who does it occur in?
- Softening of bones
- Occurs in adults
What are osteoporosis and osteopetrosis and how do each occur?
Bone diseases
Osteoporosis: Decreased bone mass & density. Nutritional deficiency, loss of bone matrix
Osteopetrosis: Increased bone mass & density. Defect of resorption by osteoclasts, makes defective bone architecture.
