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35 Cards in this Set

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  • Back
Why are we worried about regulating Ca and Phosphate?
Because low Calcium levels can cause increased nerve excitability, tetani, and death (because the diaphragm stays contracted and you can't breathe). Therefore, gotta regulate Ca2+ tightly.
What are 3 main functions of Ca?
1. Muscle contraction, release of NT/hormones,
2. Constituent of bones
3. Alters nerve excitability
What are 3 main functions of phosphate?
1. Acts as a buffer
2. Very important in ATP
3. Phosphorylates/activates things.
Where do we regulate calcium, intracelluarly or extra?
What process and movements does calcium undergo normally?
1. Deposition/resorption - bone
2. Filtration/reabsorption - kidney
3. Secretion/absorption from GI
How much calcium exchanges w/
in the normal course of a day?
-500mg is deposited/resorpted
-10,000 filtered; 9850 reabsorbd
-300 absbd from GI, 150 secreted
How much (mass) of Ca is in the extracellular fluid normally?
900 mg
What Ca rocesses can we regulate and move around for ea. organ?
1. Bone Resorption
2. Kidney Reabsorption
3. Absorption from GI
What occurs in bone metabolism, and what cells do the work?
Deposition - osteoblasts

Resorption - osteoclasts
What hormone regulates bone resorption?
Parathyroid hormones - they increase plasma [Ca]
What stimulates the release of parathyroid hormone?
low plasma calcium
Molecularly, what type of hormones are Parathyroid and Calcitonin?
PEPTIDE hormones.. therefore, they don't need a carrier, and they do need a surface receptor.
What's Parathyroid hormone's net effect on blood Calcium and phosphate levels?
Increased Ca

Decreased phosphate
What's Calcitonin's net effect on blood Calcium and phosphate levels?
Not EXACTLY opposite PTH; decreased plasma Ca, but decreased PO4 too.
What would happen if Ca and PO4 both increased in plasma?
They would precipitate and make crystals. (bad)
So, what happens when plasma Ca is increased?
Your parafollicular cells in the thyroid increase calcitonin levels to tone down Ca levels.
Other than calcitonin and parathyroid hormone, what effects plasma calcium levels?
1, 25 dihydroxycholecaciferol - aka, Vitamin D3.
What pathway stimulates Vit D3 release?
Decreased plasma Calcium, which increases PTH release, which increases 1-alpha-hydroxylase from the kidney.
What does 1-alpha-hydroxylase do?
Increases secretion of active Vit D3.
How does Vit D3 alter blood calcium?
By PROMOTING pth activity (bone resorption) and increasing plasma calcium.
What's Vit D3'hormone's net effect on blood Calcium and phosphate levels?
Calcium -> increased
PO4 -> increased
What molecule does Vitamin D3 come from originally?
How do you become Vitamin D3 deficient?
From Rickets desease.
How do you get ricket's disease?
(2 ways)
1. Lack of sunlight and vitamin d3.
2. Liver/kidney disease
Wait a sec, the net effect of Vitamin D3 is to increase BOTH phosphate and calcium !?
Well, it only happens by the action of PTH, which also decreases phosphate, so no precipitation occurs. (whew, no crystals!)
What is osteoporosis?
Loss ofbone.
What increases osteoclast production?
What inhibits cytokines?
So why do females in menopause get osteoporosis?
Because they have less estrogen, so more cytokines are around to increase osteoclast production.
What do osteoclasts do?
break down bone.
Why don't men get osteoporosis when they're old? (2 reasons)
1. Their testosterone levels don't drop off as dramatically.
2. They have more bone to begin with.
What is Rickets?
a lack of vitamin D3
What is rickets called in
Children: rickets
Adults: Osteomalacia
What is rickets a result of?
1. Decreased sunlight
2. Decreased diet
3. Kidney/liver disease
What are the results of Ricket's?
-Decreased Calcium/PO3 in plasma
-Decreased bone mineralization.