Calcium

Question 1

What are functions of calcium?

Answer 1

• Bone, tooth structure
• Mineral store
• Action potentials in cardiac muscle
• 2nd messenger (muscle: excitation-contraction coupling)

Question 2

How is calcium homeostasis achieved?

Answer 2

• Parathyroid hormone (When Low Ca2+)
• Calcitonin (When High Ca2+)
• Vitamin D

PTH & Calcitonin have exact opposite functions when regulating calcium levels

Question 3

How does parathyroid hormone work?

Answer 3

• 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

Question 4

How does Caltionin work?

Answer 4

• 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

Question 5

What are some hormones INCREASING bone formation and mass?

Answer 5

• Calcitonin
• GH
• IGF-1 (Insulin like growth factor)
• Insulin
• Oestrogen
• Testosterone

Question 6

What are some hormones DECREASING bone formation and mass?

Answer 6

• Cortisol
• Parathyroid hormone
• Thyroid hormones

Question 7

What are the 3 bone cells and what is each of their functions?

Answer 7

• 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

Question 8

What is hypo and hyper calcaemia?

Answer 8

Hypocalcemia - Reduced Ca2+

Hypercalcemia - Raised Ca2+

Question 9

What is vitamin D deficiency and what the the consequences?

Answer 9

• Dietary deficiency
• Failure to synthesise in body
• Decreased calcium uptake from GI tract -> undermineralised bone, lacks rigidity

Question 10

What is rickets and who does it occur in?

Answer 10

• Weak, soft bones, skeletal deformities
• As a result of Vit D deficiency
• Occurs in children

Question 11

What is osteomalacia and who does it occur in?

Answer 11

• Softening of bones

- Occurs in adults

Question 12

What are osteoporosis and osteopetrosis and how do each occur?

Answer 12

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.