Examples of calcium in the following topics:
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- Calcium metabolism or calcium homeostasis is the mechanism by which the body maintains adequate calcium levels.
- Calcium metabolism or calcium homeostasis is the mechanism by which the body maintains adequate calcium levels.
- Bone serves as an important storage point for calcium, as it contains 99% of the total body calcium.
- Calcium release from bone is regulated by parathyroid hormone .
- The process of bone resorption by the osteoclasts releases stored calcium into the systemic circulation and is an important process in regulating calcium balance.
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- Parathyroid hormone maintains the body's calcium levels by increasing absorption of calcium from the bones, kidneys, and GI tract.
- When blood calcium levels drop below a certain point, calcium-sensing receptors in the parathyroid gland are activated, and the parathyroid glands release parathyroid hormone into the blood.
- Parathyroid hormone acts to increase blood calcium levels, while calcitonin acts to decrease blood calcium levels.
- Parathyroid hormone acts on the bone to increase blood calcium levels by stimulating osteoclasts to break down bone, releasing calcium into the bloodstream.
- It acts on the kidneys to increase blood calcium levels by promoting calcium reabsorption in the nephrons.
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- Cardiac muscle fibers undergo coordinated contraction via calcium-induced calcium release, conducted through the intercalated discs.
- In cardiac muscle, ECC is dependent on a phenomenon called calcium-induced calcium release (CICR), which involves the influx of calcium ions into the cell triggering further release of ions into the cytoplasm.
- The mechanism for CIRC is that receptors within the cardiomyocyte will bind to calcium ions when calcium ion channels open during depolarization, and will release more calcium ions into the cell.
- As the action potential travels between sarcomeres, it activates the calcium channels in the T-tubules, resulting in an influx of calcium ions into the cardiomyocyte.
- Calcium in the cytoplasm then binds to cardiac troponin-C, which moves the troponin complex away from the actin binding site.
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- Calcium is a very important electrolyte.
- In the typical Australian diet, there is about 1200 mg/d of calcium.
- There is also a constant loss of calcium via the kidneys even if there is none in the diet.
- Calcium in plasma exists in three forms: ionized, nonionized and protein bound.
- This increases ionized calcium levels by increasing bone re-absorption, decreasing renal excretion and acting on the kidney to increase the rate of formation of active Vitamin D, thereby increasing gut absorption of calcium.
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- Parathyroid glands control the amount of calcium in the blood and within the bones.
- When blood calcium levels drop below a certain point, calcium-sensing receptors in the parathyroid gland are activated to release hormone into the blood.
- Parathyroid hormone (PTH, also known as parathormone) is a small protein that takes part in the control of calcium and phosphate homeostasis, as well as bone physiology.
- PTH increases blood calcium levels by stimulating osteoclasts to break down bone and release calcium.
- PTH also increases gastrointestinal calcium absorption by activating vitamin D, and promotes calcium conservation (reabsorption) by the kidneys.
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- When stimulated a signal transduction cascade leads to increased intracellular calcium from the sarcoplasmic reticulum through IP3 mediated calcium release, as well as enhanced calcium entry across the sarcolemma through calcium channels.
- The rise in intracellular calcium complexes with calmodulin, which in turn activates myosin light chain kinase.
- Once elevated, the intracellular calcium concentration is returned to its basal level through a variety of protein pumps and calcium exchangers located on the plasma membrane and sarcoplasmic reticulum.
- This reduction in calcium removes the stimulus necessary for contraction allowing for a return to baseline.
- Dephosphorylation by myosin light-chain phosphatase and induction of calcium symportersand antiporters that pump calcium ions out of the intracellular compartment both contribute to smooth muscle cell relaxation and therefore vasodilation.
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- It is stimulated or inhibited by signals from other parts of the body, depending on the demand for calcium.
- Calcium-sensing membrane receptors in the parathyroid gland monitor calcium levels in the extracellular fluid.
- Low levels of calcium stimulates the release of parathyroid hormone (PTH) from chief cells of the parathyroid gland.
- High levels of calcium in the blood, on the other hand, lead to decreased PTH release from the parathyroid gland.
- Medication includes calcium, vitamin D, bisphosphonates, and several others.
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- Vitamin K, calcium, and phospholipids are necessary cofactors for proper coagulation, and those deficient in these substances will be more susceptible to uncontrolled bleeding.
- Calcium and phospholipids (a platelet membrane constituent) are
required cofactors prothrombin activation enzyme complexes to function.
- Calcium acts as a catalyst for this reaction, speeding up the rate of the reaction to occur within the timeframe of the factors involved in the coagulation cascade.
- Calcium is also required to to synthesize the anticoagulant Protein C (along with vitamin K).
- Deficiencies in calcium will inhibit proper blood coagulation, such as a nutritional deficiency or acute problems in which calcium is allocated elsewhere in the blood, as it has many other functions, such as vitamin D metabolism and neuromususcular signaling.
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- ATP is no longer provided to operate the SERCA pumps in the membrane of the sarcoplasmic reticulum; these pumps move calcium ions into the terminal cisternae.
- Physiologically, rigor mortis is caused a release of calcium facilitating crossbridges in the sarcomeres; the coupling between myosin and actin cannot be broken, creating a constant state of muscle contraction until enzymatic decomposition eventually removes the crossbridges.
- This release of calcium is caused by the loss of ATP-mediated function of calcium pumps of the sarcoplasmic reticulum, due to ATP depletion in the absence of cellular respiration.
- Diffusion of the calcium through the pumps occurs, facilitation binding of myosin and actin filaments.
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- If a patient has elevated calcium, several different types of tests can be used to locate the abnormal glands.
- In secondary HPT, the parathyroid glands make too much parathyroid hormone (PTH) because the kidneys have failed, and the calcium and phosphorus are out of balance.
- Most experts believe that Sensipar should not be used for patients with primary hyperparathyroidism (patients that have a high calcium and are not on kidney dialysis).
- This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany (involuntary muscle contraction), and several other symptoms.
- Patients have a low serum calcium and high phosphate, but the parathyroid hormone level (PTH) is actually appropriately high (due to the hypocalcemia).