Lecture 73 Flashcards
Many physiological processes depend on ____________ and ____________ availability
Ca and P
Regulatory system to maintain extracellular fluid levels of Ca and P include:
- Vit D
- Parathyroid hormone
- calcitonin
Processes in which Ca is involved
neurotransmission, Learning and memory, muscle contraction, mitosis, mobility, secretion, fertilization, blood clotting, structure of bones and teeth
Is Ca higher extracellularly or intracellularly
extracellularly
how much calcium is ionized (free form)
50 percent
Why is Ca conc higher extracellularly?
Membranes are very impermeable to Ca
How much calcium is bound (albumin, proteins) calcium?
40 percent
We need ionized Ca to remain in normal range (50%). This depends on pH. If pH is low acidosis can cause ____________ to Ca?
Increases ionized Ca channels
Complexed calcium (anions: phosphate and bicarb) is how much of calcium
10 percent
Intracellular Ca has a lower ?
Concentration
Cytosolic (intracellular) Ca can be increased as need-
fine balance of control
If Ca intake goes down, body adjust by increasing?
Percentage of Ca absorbed
Ca-sensing by Ca receptors on endocrine cells is involved in?
Ca homeostasis
____________ is hypocalcemia?
Low calcium levels
____________ is a common cause of hypocalcemia in animals?
- Lactation
- parathyroid and Vit D disorders
- gut metabolism
- renal failure
- ethylone glycol toxicity
Twitching/cramping of skeletal muscles and numbness/tingling, seizures can be due to?
Hypocalcemia
Low or high levels of plasma Ca is talking about?
Ionized Ca
Increased in plasma Ca (ionized Ca)
Hypercalcemia
constipation, polyuria, polydipsia, lethargy, coma and death can be caused due to?
Hypercalcemia
____________ can cause Hypercalcemia?
Parathyroid disorders and Vit D toxicity
Changes in plasma protein concentration can alter?
Ca in plasma
____________ can lead to altering Ca in plasma?
Changes in protein concentrations, complexing anion concentration and acid-base disturbances
Change the fraction of Ca bound to plasma albumin
Acid-base disturbance
Albumin can bind ____________ or ____________ ions
H+, Ca2+
more H ions in blood, more H ions bound to albumin, free ionized Ca increases. ____________ is this?
Acidemia
Acidemia can cause?
hypercalcemia
Less h ions in blood, more Ca bind to albumin, ionized Ca in blood decreases. ____________ is this?
Alkalemia
Alkalemia can lead to?
Hypocalcemia
interaction of bone, kidney, and intestines, plus parathyroid hormone, calcitonin and vit D
Calcium homeostasis
bone is constantly remodeled so Ca can be ____________ from blood
released or absorbed
____________ stimulates bone resorption of Ca
Parathyroid hormone and Vit D
____________ inhibits bone resorption of Ca?
Calcitonin
intestine will absorb Ca but the amount is regulated by?
Vitamin D
Absorption of Ca in the intestines decreases/increases with age
Decreases
Excess Ca in the diet is excreted where?
Shit
Kidneys reabsorb Ca- which is regulated by?
PTH
98% of filtered Ca is reabsorbed where?
Kidney
____________ is a component of ATP, various cofactors, lipids, RNA, DNA and bone
Phosphate
Percentage of phosphate absorbed from the diet is ____________
constant
Phosphate helps to balance many?
Cations
How is regulation of P balance maintained
urinary excretion
where is phosphate stored?
Muscles
necessary for neuromuscular transmission
Magnesium
Magnesium is a cofactor in ____________ reactions
enzyme
Dietary Mg absorbed by gut and is ____________ by vit D
enhanced
Where is Mg excreted?
Urine
How many parathyroid glands are there and ____________ do they contain?
4 parathyroid glands. Contain chief cells and oxyphil cells
Chief cells are a source of?
ATP
PTH sustain/increases ____________
plasma Ca
PTH stimulates an increase in Ca so it stimulates
reabsorption in bone and kidney
PTH decreases/prevents increase in ____________
Plasma P
PTH causes ____________ to happen with phosphorus?
Increase phosphorus excretion in kidneys
Ca receptors on parathyroid cells are activated when plasma Ca levels ____________
Falls
When plasma Ca is high ____________ is inhibited?
Ca receptor on parathyroid cells (causes degradation of granules)
Increased blood phosphate increases PTH secretion via ____________
P receptor
PTH also stimulates vitamin D synthesis. Vit D feed back to PTH to?
inhibit PTH
____________ are stimulators of PTH release?
Decreased blood Ca, Increased blood phosphate, Decreased Mg
When Vit D inhibits PTH release ____________ does this cause?
Increases blood Ca
PTH binds to plasma membrane receptors and activates ____________
G-protein/cAMP
____________ does PTH target?
Bones, kidneys and intestines
A decrease in plasma Ca concentration leads to an increase in?
PTH secretion
PTH ____________ bone resorption to release Ca and P into blood
Increases
PTH stimulates Ca reabsorption in ____________ in the kidneys
Distal convoluted tubule
PTH inhibits phosphate reabsorption in ____________ of kidneys thus causing P excretion in urine
Proximal convoluted tubules
PTH increases Mg reabsorption in the ____________
Kidneys
PTH stimulates vit D ____________
synthesis in the kidney
PTH increases Ca absorption from intestines via
Vitamin D
caused by benign tumor or hyperplasia of one or both parathyroid glands
Hyperparathyroidism
____________ is the primary form of hyperparathyroidism
benign tumor or hyperplasia
An increase of PTH, hypercalcemia, hypophosphatemia, renal calculi and bone pain and fractures are clinical signs of ____________?
Benign tumor or hyperplasia in parathyroid gland
Caused by increased phosphate in blood, which precipitates Ca result in hypocalcemia - causes secondary increase in PTH
Secondary form of hyperparathyroidism
Secondary form of hyperparathyroidism : increased phosphate in blood, which precipitates Ca result in hypocalcemia CAUSES?
secondary increase in PTH
Secondary form of hyperparathyroidism may results from?
Renal failure or increased dietary phosphate
Accidental surgical removal, autoimmune destruction and idiopathic may cause?
Hypoparathyroidism
Hypoparathyroidism results in?
Decreased PTH, Hypocalcemia, hyperphosphatemia
Synthesized as preprohormone by parafollicular cells of the thyroid gland
Calcitonin
Calcitonin decreases blood Ca and P by?
inhibiting bone resorption, increasing urinary P excretion, inhibiting renal reabsorption of Ca
Increased blood Ca, Vitamin D (via feedback), ingested food are stimulators for
Simulators of calcitonin
Stimulators of calcitonin: Vit D (via feedback) why is this a stimulator of calcitonin?
No need for release from bone or to reabsorb via kidneys
Required for bone formation and increases Ca absorption from GIT
Synthesis of Vit D
Vitamin D is synthesized from hormones and vitamin from diet. ____________ vit D is synthesized and ____________ is from the diet?
Synthesized (D3) and Diet (D2 or D3)
Synthesized Vit D in skin: precursor is
7-dehydroxyvitamin D
After synthesis or absorption of Vit D in gut it goes to the
Liver
In the liver Vit D is converted to
25-hydroxyvitamin D
25-hydroxyvitamin D does to the kideny and most is converted to ?
1,25 Dihydroxyvitamin D
intermediates and active vit D circulates bound to?
protein carriers
Vitamin D is _______ so can be stored in liver and adipose
Fat-soluble
Toxicity of vitamin D results in _________________________
hypercalcemia, renal failure, elevated phosphate (soft tissue calcification)
Metabolism of vit D is excreted in
Bile
Most actions of vit D happens in
intestine
Vit D stimulates Ca absorption of calbindin and stimulates absorption of?
Mg and phosphate in intestine
Vit D weakly stimulates ____________ reabsorption in kidneys
Ca and P
Calcium absorption can be
active or passive
Active, transcellular process dominates when _________
Ca intake low
Passive absorption (jejunum and ileum), paracellular proces dominates
Ca intake high
Active, transcellular process requires
Vit D
Vitamine D acts through cytosolic receptor and increases ___________
production of calbindin
Calbindin binds ca inside cells and facilitates transports to ________
Basolateral membrane
Vit D stimulates bone resorption in presence of ?
PTH
Vit D Increases Ca transport and uptake by SR in
skeletal muscles
VIT D ___________ PTH synthesis
Decreases
Muscle weakness, abnormal contractions, rickets, bone fractures and cardiac dysfunction is a result of?
Deficiency of Vit D