L22 Flashcards
what is rickets
Rickets – due to a deficiency or impaired
metabolism of vitamin D, calcium or phosphorus.
The predominant cause is vitamin D deficiency.
what activates metabilisum of vitamin D
The kidney activates metabilisum of vitamin D
describe the difference between healthy bones and bones of those with rickets
Normal individual has a thick bone and quite ossified (little openings)
In rickets the bones are think an the bones are porous, they get bone softening and troubles with their teeth, they also have muscle weakness
what is osteoporosis
Osteoporosis is when the bone mass and density is reduced. They have very weak bones and have a high incidence of hip replacement as they fall over and break the bones which then need to be replaced. They also have lots of knee replacement
what % of new zealanders are lactose intolerant
10%
Ca homeostasis is a balance between what organs
kidney, intestine and bone
daily intake of Ca = daily Ca excreted
what % of Ca is excreted in feces and urine
feces = 80% (800mg ish)
urine 20% (200mg ish)
what is the concentration of Ca in the body
bone/teeth, ICF and ECF
bone/teeth = 99% of the bosies Ca
- ICF = generally < 0.1 µM (1%)
- ECF = 2-3 mM (0.1%)
what Ca concentrations define hyper and hypocalcemia
–ECF > 3 mM = hypercalcemia (High Ca2+ blood)
–ECF < 2 mM = hypocalcemia (Low Ca2+ blood)
Why is it important to maintain appropriate ICF and ECF concentrations of Ca2+?
theres 8
- proper bone formation
- neurotransmission (release of vesical)
- mitosis, cell division and growth
- muscle contraction
- blood clotting
- growth
- enzymatic reactions
- 2nd messenger function
what does hypocalcemia (low ECF Ca) cause
• increase excitability of:
– nerve cells
– muscle cells
• pins and needles • airway obstruction (increase in mucus) • epileptic seizures • cardiac arrhythmias • hypocalcemia tetany – muscle spasms
what does hypercalcemia (high ECF Ca) cause
• decrease excitability of:
– nerve cells
– muscle cells
- disorientation
- lethargy (lack of energy)
- cardiac arrhythmias
- death
Which of the following statements is TRUE?
A. The bulk of Ca 2+ in the body is located within the ICF.
B. Low ECF Ca2+ causes decreased excitability of nerve cells.
C. The ECF Ca2+ concentration is between 2-3 mM.
D. Osteoporosis causes and increase in bone mass
A. bulk in bone/teeth
B. causes increased excitability. decreased outside = increased inside as things are relative (I think)
D. decrease in bone mas
C is correct
how is Ca found in the plasma
3 ways
• 50% of the Ca2+ is ionized
• 40% of the Ca2+ is bound to protein
(normally albumin), thus not filtered
• 10% of the Ca2+ is complexed with anions (HCO3, citrate, phosphate, SO4=)
So, only 60% of the plasma Ca2+ can be filtered!
what % of Ca in the plasma can be filtered
60%
what % of Ca in the plasma can be filtered
60%
as the 40% bound to albumin is not filtered (proteins can’t get through the filtration barrier)
what is the equation for dailey filtered load of an ion
eg Ca
GFR x [Ca2+]plasma = Daily filtered load
180 L/day x 2.5 mmol/L = 450 mmoles/day
(filtered)
what % of Ca does the PT reabsorb
50-60% of the filtered load of Ca
how does the PT reabsorb Ca
Ca transport is 100% via the paracellular pathway
occurs via solvent drag
what % of Ca does the thick ascending limb reabsorb
15% of daily filtered load of Ca
how does Ca get reabsorbed in the thick ascending limb
paracellular pathway
what controls the permeability of the tight junctions of the thick ascending limb
- Claudin-16 plays a role in maintaining the permeability of the tight junctions that favours transport and Ca2+, Mg2+ and Na +
where is the Ca sensor receptor located
on the basolateral membrane of the thick ascending limb
what is the role of the CaSR
it monitors the ECF concentration of Ca
If you are in hypERcalcenia it will be detected by the Ca sensor receptor which will alter the function (downregulate) NKCC and the K channel (ROMK)
Under hyPOclacemic conditions it will not down regulate
