Final: Calcium (Ca) Flashcards
What are the functions of intracellular Ca?
Critical for enzyme activity and cell function (Endocrinology), 2nd messenger for hormone signals
(1/10,000 of EC Ca)
What are the functions of extracellular Ca?
Skeletal tissue, transmission of nerve impulses, excitation of skeletal and cardiac muscles, blood clotting, component of milk and eggshells
Where is most of body Ca found and what %?
Bone; 99.5%
What are normal plasma Ca [ ]s?
10 mg/dL OR
2.5 mM/L OR
5 mEq/L
What % of Ca is bound to protein?
45%
What % of Ca is bound to anions?
5%
What % of Ca is ionized?
50%
What are Ca levels in ACUTE hypocalcemia?
< 6.5 mg/dL
What are Ca levels in CHRONIC hypocalcemia?
< 9 mg/dL
What are symptoms of acute hypocalcemia?
Hyperexcitable nerves –> tetany
Lack of excitation across myoneural junction –> paresis
Reduced cardiac muscle strength = reduced cardiac output
What are symptoms of chronic hypocalcemia?
Bone dissolution, osteoporosis, osteodystrophy
What are Ca levels in hypercalcemia?
> 11.5 mg/dL
What are symptoms of hypercalcemia?
Calcification of soft tissues (esp. kidney)
What happens physiologically to induce flaccid paralysis in ruminants?
Hypocalcemia –> lack of Ca prevents release of ACh at motor end plate
What is the predominant clinical sign of hypocalcemia in ruminants?
Flaccid paralysis
What is the predominant clinical sign of hypocalcemia in non-ruminants?
tetany
What gland can sense any reduction in blood Ca concentration and where is it located?
Parathyroid glands; near the thyroid
What level of blood Ca is critical?
9-10 mg/dL
How do parathyroid glands respond to low levels of Ca?
Secrete PTH into blood
What type of bone is usually affected by PTH?
Spongy/trabecular bone
What occurs during osteocytic osteolysis?
PTH stimulates osteocytes to pump Ca from canaliculi back into the extracellular fluid.
Osteoclasts are under control of _____.
PTH
Active transport of Ca is controlled by _____.
1,25-dihydroxyvitamin D
What is produced by the thyroid gland in response to hypercalcemia?
calcitonin
What 2 things does calcitonin do?
- Inhibits renal reabsorption of Ca from glomerular filtrate
- Inhibits bone Ca resorption
What are good sources of Ca?
Ca carbonate or Ca chloride, forages, legumes
What are poor sources of Ca?
Grains
What are some diseases of Ca deficiency?
- Rickets in younger animals (although usually by Vit D or Phos deficiency)
- Osteoporosis/osteomalacia (adult Rickets)
- Lactational osteoporosis
- Caged layer fatigue
- Nutritional Secondary Hyperparathyroidism
What are some symptoms of rickets in young animals?
Widened growth plate, enlarged/painful joints, bowing of legs, short stature, costochondral junctions readily palpable, bones rubbery and easy to bend, rosary bead lesions, fractures
What are symptoms of osteomalacia (adult rickets)?
Lesion at sites of bone remodeling
What happens in osteoporosis?
Animal needs to pull Ca, so pulls it from bones
What is lactational osteoporosis?
Bone is sacrificed to keep Ca levels normal in milk and blood; is reversible
What is NSHP?
Diet Ca is inadequate so body responds by increasing PTH.
- Increases renal reabsorption of Ca
- Increases osteoclastic bone resorption
- Bone Ca content reduced
- Production of 1,25-dihydroxyvitamin D increased
What is osteodystrophy?
Ca deficiency accompanied by excessive Phos in adults
“Rubber jaw” and loose teeth
What is osteolysis?
Sites of bone radiolucency - secondary to infection and inflammation of bone region
What is Bighead disease?
NSPH of horses caused by diets high in P and low in Ca
- Excessive grain feeding (high phytate)
- High levels of oxalate in hay = prevents Ca absorption
What are symptoms of Bighead disease?
Thickened flat bones of skull to give head a swollen appearance
Shifting lameness due to tendon and ligament avulsions, bone microfractures
What are 3 reasons why iguanas and turtles in captivity may develop NSPH?
- Diets based on meat or fruits (no Ca) (add limestone)
- Diets low in vitamin D and animals caged indoors (need sun lamps)
- Temp may be too low to promote diet digestion (keep temp high)
What is caged layer fatigue?
Hen with hypocalcemia utilizes bone Ca to provide eggs with Ca, results in leg fractures/osteoporosis.
What is milk fever?
Calcium deficiency (and metabolic alkalosis), occurs mainly in cows after calving but can also occur in goats. (Blood Ca goes < 5mg/dL)
What is the tx for milk fever?
IV Ca immediately
What can cause milk fever?
Pre-calving diets that are too high in K and/or Na, and also hypomagnesemia.
How can you prevent milk fever?
Feed low K, high Ca diets before calving. (any anion, really, will help prevent alkalosis)
