Drug affecting inorganic metabolism
1-sodium Na
sodium is the main extracellular cation.
sodium is responsible for osmotic pressure
sodium is present outside the cell and potassium inside cell,when action potential ocuurs ,potassium extrude outside the cell and sodium enter----->leading to increase permeability of cell membrane
deficiency of sodium is due to dehydration which result from vomiting and diarrohea.
2-potassium
potassium is the main intra cellular cation
play role in depolarization
depress heart muscle ,so when high increase is in blood ,causes cardiac arrest.
in starvation and injury,protein catabolism release large amount of potassium excreted by kidney causing kidney damage.
used as diuretics in horse ,cow and poultry as potassium citrate,potassium acetate and potassium chloride.
used to restore acid base balance.
3-calcium
calcium is cation present mainly in the bone,35% is bound to plasma proteins.15% is bound to bicarbonateand 50% is ionized(physiologically active)
Ca is slowly absorbed from first part of small intestine and decrease in alkaline media.
factor affecting Ca metabolism
1-parathyroid hormone:increase Ca in blood by increase mobilization Ca from bone .kidney and increase absorption by intestine.
2-steroidal hormones:as estrogen ,progestron and testosteron.which cause Ca retention.
3-adrenocortical hormone:causing Ca loss
4-thyrocalcitonin:decrease Ca and po4 level,secreted from thyroid gland and antagonize parathyroid hormone
6-vitamin D:necessary for bone calcification ,deficiency of vit D cauing rickets while extra vitamin D causing deposit Ca in vital organs resulting in calculi formation and gout.
calcium function
1-Ca competes with Na on their sites on cell membrane .so the permeability of cell membrane to Na decrease with excess Ca .
2-contraction of muscle
3-involved in stimuli and endocrine secretion as ADH and adrenaline by Ach.
4-necessary for Na pump to extrude Na during depolarization
calcium deficiency causes
1-tetanic spasm
2-decrease some endocrine secretion
3-milk fever
calcium excess
1-hypotonia
2-weak muscle
3-decrease contractility due to decrease Na permeability
4-decrease activity of smooth muscle results in constipation , indigestion and decrease appetite
5-deposit vitamin D in vital organ
magnisum
function:
1-inhibit release of Ach in nerve muscular junction
2-decrease sensitivity of motor end plate to Ach (increase Ach synthesis)
3-increase synthesis of choline acetylase enzyme
4-maintain contractility of muscle
5-activate certain enzyme as ATPase,pyruvic phosphatase ,fructokinase and adenyl cyclase
6-depress CNS and respiratory center
used in
1-as skeletal muscle relaxant
2-treatment hypomagnesemia
3-MgSo4 as bulk purgative and I/V for destroy dogs
4-Mg carbonate as anti acid
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