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35 Cards in this Set
- Front
- Back
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Why are we worried about regulating Ca and Phosphate?
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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.
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What are 3 main functions of Ca?
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1. Muscle contraction, release of NT/hormones,
2. Constituent of bones 3. Alters nerve excitability |
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What are 3 main functions of phosphate?
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1. Acts as a buffer
2. Very important in ATP 3. Phosphorylates/activates things. |
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Where do we regulate calcium, intracelluarly or extra?
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Extracellular.
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What process and movements does calcium undergo normally?
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1. Deposition/resorption - bone
2. Filtration/reabsorption - kidney 3. Secretion/absorption from GI |
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How much calcium exchanges w/
-BONES -KIDNEY -GI TRACT in the normal course of a day? |
-500mg is deposited/resorpted
-10,000 filtered; 9850 reabsorbd -300 absbd from GI, 150 secreted |
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How much (mass) of Ca is in the extracellular fluid normally?
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900 mg
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What Ca rocesses can we regulate and move around for ea. organ?
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1. Bone Resorption
2. Kidney Reabsorption 3. Absorption from GI |
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What occurs in bone metabolism, and what cells do the work?
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Deposition - osteoblasts
Resorption - osteoclasts |
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What hormone regulates bone resorption?
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Parathyroid hormones - they increase plasma [Ca]
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What stimulates the release of parathyroid hormone?
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low plasma calcium
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Molecularly, what type of hormones are Parathyroid and Calcitonin?
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PEPTIDE hormones.. therefore, they don't need a carrier, and they do need a surface receptor.
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What's Parathyroid hormone's net effect on blood Calcium and phosphate levels?
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Increased Ca
Decreased phosphate |
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What's Calcitonin's net effect on blood Calcium and phosphate levels?
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Not EXACTLY opposite PTH; decreased plasma Ca, but decreased PO4 too.
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What would happen if Ca and PO4 both increased in plasma?
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They would precipitate and make crystals. (bad)
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So, what happens when plasma Ca is increased?
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Your parafollicular cells in the thyroid increase calcitonin levels to tone down Ca levels.
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Other than calcitonin and parathyroid hormone, what effects plasma calcium levels?
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1, 25 dihydroxycholecaciferol - aka, Vitamin D3.
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What pathway stimulates Vit D3 release?
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Decreased plasma Calcium, which increases PTH release, which increases 1-alpha-hydroxylase from the kidney.
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What does 1-alpha-hydroxylase do?
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Increases secretion of active Vit D3.
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How does Vit D3 alter blood calcium?
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By PROMOTING pth activity (bone resorption) and increasing plasma calcium.
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What's Vit D3'hormone's net effect on blood Calcium and phosphate levels?
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Calcium -> increased
PO4 -> increased |
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What molecule does Vitamin D3 come from originally?
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Cholesterol
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How do you become Vitamin D3 deficient?
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From Rickets desease.
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How do you get ricket's disease?
(2 ways) |
1. Lack of sunlight and vitamin d3.
2. Liver/kidney disease |
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Wait a sec, the net effect of Vitamin D3 is to increase BOTH phosphate and calcium !?
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Well, it only happens by the action of PTH, which also decreases phosphate, so no precipitation occurs. (whew, no crystals!)
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What is osteoporosis?
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Loss ofbone.
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What increases osteoclast production?
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Cytokines.
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What inhibits cytokines?
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Estrogen
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So why do females in menopause get osteoporosis?
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Because they have less estrogen, so more cytokines are around to increase osteoclast production.
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What do osteoclasts do?
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break down bone.
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Why don't men get osteoporosis when they're old? (2 reasons)
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1. Their testosterone levels don't drop off as dramatically.
2. They have more bone to begin with. |
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What is Rickets?
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a lack of vitamin D3
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What is rickets called in
-Children -Adults |
Children: rickets
Adults: Osteomalacia |
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What is rickets a result of?
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1. Decreased sunlight
2. Decreased diet 3. Kidney/liver disease |
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What are the results of Ricket's?
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-Decreased Calcium/PO3 in plasma
-Decreased bone mineralization. |
