Calcium Homeostasis

Question 1

Name 5 roles of Ca within the body?

Answer 1

Signalling
Blood clotting
Apoptosis
Skeletal strength
Membrane Excitability

Question 2

What are the effects of Hypocalcaemia within the body ?

Answer 2

An increase in Na permeability causes hyperexcitation of neurons. In extreme cases can cause tetany and asphyxiation.

Question 3

What are the effects of Hypercalcaemia within the body?

Answer 3

Can be caused byb an overproduction of PTH. Decreases in Na permeability can reduce excitability and depress NM activity. In extreme cases can cause arrhythmias.

Question 4

Binding capacity of Ca is increased in what kind of conditions?

Answer 4

Alkalotic conditions

Question 5

What are the 2 hormones which act to increase Ca within the plasma

Answer 5

Calcitriol

PTH

Question 6

What is another name for the active for of vitamin D?

Answer 6

Calcitriol

Question 7

Where is Calcitriol produced?

Answer 7

Liver and Kidneys

Question 8

How does PTH increase plasma Ca?

Answer 8

Stimulates Osteoclasts
Inhibits osteoblasts
Increase reabsorption of Ca at kidney tubules
Increase renal excretion of phosphates
Stimulates kidney to synthesize Calcitriol from Vitamin D

Question 9

What are the 2 ways in which Vitamin D is formed?

Answer 9

Cholesterol derived from action of UV light on the skin

Dietary

Question 10

What is the main action of Calcitriol in order to increase plasma Ca?

Answer 10

Increase Ca transporters within the gut
Facilitates renal absorption of Ca
Mobilizes Ca stores by stimulating osteoclast activity

Question 11

What is the name of the hormone which acts to decrease plasma Ca levels and which gland secretes this ?

Answer 11

Calcitonin and thyroid gland