Calcium Homeostasis Flashcards
list the roles of calcium in the body
- signalling (synaptic vesicles, neurotransmitters. muscle contraction)
- blood clotting
- apoptosis
- skeletal strength
- membrane excitability
what effect does calcium have on Na permeability
calcium decreases Na permeability
why is there hyperexcitation of neurons in hypocalcaemia
as calcium decreases Na permeability, if there is less calcium present then this increases neuronal Na permeability
what effect does hypercalcaemia have on neuronal Na permeability
hypercalcaemia decreases neuronal Na permeability which will reduce excitability and depress neuromuscular activity
were is 99% of calcium in our body
in our bones
apart from our bone where else is calcium stored in the body
- 9% in intracellular fluid (mostly inside mitochondria and sarcoplasmic reticulum)
- 1% in extracellular fluid (nearly half of ECF Ca is bound to protein)
what form is calcium stored in the bone
hydroxyapatite (Ca10(PO4)6(OH)2)
calcium has a very high affinity for proteins why is this
as it is a small positive charge it will be attracted to large negative charge such as proteins
in plasma how much of total calcium present is bound to plasma proteins
40% is bound to plasma proteins
in the blood 40% of calcium is bound to protein, of this 40% how much is bound to albumin? how much is bound to globulin?
Albumin 80%
Globulin 20%
what percentage of calcium in the blood is free(ionised)
50%
free(ionised) calcium can form complexes with what
can form complexes with free anions to give for example, calcium carbonate
what is an anion
a negatively charged ion
the binding capacity of plasma proteins change with pH true or false
true
in relation to pH when does the binding capacity of plasma proteins increase
binding capacity is increased under alkalotic conditions
what effect does alkalosis have on protein bound calcium
alkalosis increases protein bound calcium
what effect does acidosis have on protein bound calcium
acidosis decreases protein bound calcium therefore free [Ca2+]plasma rises
the calcium in bone can be added to or released as required true or false
true
what are osteoblasts
known as the bone building cells, they are the cells that form new bone
what do osteoblasts differentiate into
osteocytes
what do osteocytes do
they are much less active than osteoblasts, they regulate the activity of osteoblasts and osteoclasts
what are osteoclasts
is a type of bone cell that breaks down bone tissue by secreting H+ ions and proteolytic enzymes to dissolve ECM
two key hormones act to increase [Ca2+]plasma what are they
parathyroid hormone (PTH) calcitriol(active form of Vit D)
what is parathyroid hormone and where is it produced
it is a polypeptide hormone produced by the parathyroid glands
