Lecture 22 Flashcards
(34 cards)
What causes rickets?
due to a deficiency or impaired metabolism of vitamin D, calcium or phosphorus. The predominant cause is vitamin D deficiency
What activates vitamin D3?
the kidneys
The Ca2+ you can deal with depends on what?
your diet
Ca2+ homeostasis is a balance between that three things?
- kidneys
- intestine
- bone
Daily Ca+ intake equals what? What does this mean for the net?
daily Ca2+ excreted
net = 0
How much Ca2+ do we typically take in from our diet?
1000 mg
How much Ca2+ do we excrete in our faeces
800 mg
How much Ca2+ do we excrete in our urine?
200 mg
If our Ca2+ is too low, where so we get it from?
we break down bone to get it
Where is most of the Ca2+ in our body stored? What percentage does this make up?
bone and teeth
99%
What is the concentration of Ca2+ in the ICF? What percent does this make up?
generally < 0.1 μM (1%)
What is the concentration of Ca2+ in the ECF? What percent does this make up?
2-3 mM (0.1%)
What is the concentration of Ca2+ in the ECF that results in hypercalcemia?
ECF > 3 mM = hypercalcemia
High Ca2+ blood
What is the concentration of Ca2+ in the ECF that results in hypocalcemia?
< 2 mM = hypocalcemia (Low Ca2+ blood)
Why is it important to maintain appropriate ICF and ECF concentrations of Ca2+? • proper \_\_\_\_\_\_\_\_ formation • \_\_\_\_\_\_\_\_\_\_\_ • \_\_\_\_\_\_\_, cell \_\_\_\_\_\_ and \_\_\_\_\_\_\_\_ • muscle \_\_\_\_\_\_\_\_ • blood \_\_\_\_\_\_\_ • \_\_\_\_\_\_\_\_ • \_\_\_\_\_\_\_\_\_ reactions • \_\_\_\_\_\_\_\_ messenger function
- proper bone formation
- neurotransmission
- mitosis, cell division and growth
- muscle contraction
- blood clotting
- growth
- enzymatic reactions
- 2nd messenger function
What are 6 problems with low ECF Ca2+? • increase \_\_\_\_\_\_\_\_ of: – \_\_\_\_\_\_\_\_ cells – \_\_\_\_\_\_\_ cells • '\_\_\_\_\_\_ and \_\_\_\_\_\_\_' • \_\_\_\_\_\_\_ obstruction • \_\_\_\_\_\_ seizures • cardiac \_\_\_\_\_\_\_\_ • hypocalcemia \_\_\_\_\_\_\_ – muscle \_\_\_\_\_\_\_
• increase excitability of: – nerve cells – muscle cells • 'pins and needles' • airway obstruction • epileptic seizures • cardiac arrhythmias • hypocalcemia tetany – muscle spasms
What are problems with high ECF Ca2+? - decrease \_\_\_\_\_\_ of: – \_\_\_\_\_ cells – \_\_\_\_\_\_ cells - disorientation \_\_\_\_\_\_ - cardiac \_\_\_\_\_\_ - \_\_\_\_\_\_
- decrease excitability of: – nerve cells – muscle cells - disorientation lethargy - 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.
C. The ECF Ca2+ concentration is between 2-3 mM.
In what three forms is Ca2+ held in the plasma? What percentages do each of these forms make up?
• 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 (HCO-3, citrate, phosphate,
SO4=)
How much of the Ca2+ in the plasma can be filtered?
60%
Calculate the daily filtered load of Ca2+ given that the [Ca2+]plasma is 2.5 mmol/L
180 L/day x 2.5 mmol/L = 450 mmoles/day (filtered)
Which parts of the nephron reabsorb Ca2+ and what percentage of the Ca2+ load do each of there make up?
PT: 50-60% thick ascending loop: 15% DT: 10-15% CCD: 1% 1% is excreted
How is Ca2+ reabsorbed in the proximal tubule?
This is purely through the paracellular pathway (solvent drag) due to the PT having leaky absorptive epithelium. The lumen is + charged as so Ca2+ leaves
What is solvent drag?
refers to solutes in the ultrafiltrate that are transported back from the renal tubule by the flow of water rather than specifically by ion pumps or other membrane transport proteins
