Mineral Homeostasis Quiz
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Questions and Answers

What effect does an acidic pH in the intestine have on calcium absorption?

  • Increases calcium solubility (correct)
  • Has no effect on calcium absorption
  • Decreases calcium solubility
  • Forms insoluble calcium soaps

Which hormone is responsible for increasing active calcium absorption?

  • Cortisol
  • Vitamin D (correct)
  • Insulin
  • Aldosterone

In which part of the nephron is about 60% of filtered calcium reabsorbed?

  • Loop of Henle
  • Distal tubules
  • Proximal tubules (correct)
  • Collecting ducts

How does hypercalcemia affect neuronal excitability?

<p>Depresses neural function (D)</p> Signup and view all the answers

What dietary component decreases calcium absorption?

<p>Fats (A)</p> Signup and view all the answers

Which hormone decreases when there is hypercalcemia?

<p>Parathyroid hormone (PTH) (D)</p> Signup and view all the answers

What is the primary role of phosphate in the body?

<p>Formation of bones and teeth (B)</p> Signup and view all the answers

Which of the following correctly describes the role of calcium in relation to the excitable cells?

<p>Influences neuronal membrane permeability (D)</p> Signup and view all the answers

What impact does high intake of calcium salts have on phosphate absorption?

<p>It inhibits phosphate absorption from the gut. (C)</p> Signup and view all the answers

Which form of vitamin D is primarily obtained from sunlight exposure?

<p>Cholecalciferol (C)</p> Signup and view all the answers

What role does parathyroid hormone (PTH) play in phosphate homeostasis?

<p>Inhibits the reabsorption of filtered Pi in the kidneys. (C)</p> Signup and view all the answers

Which of the following is NOT a good dietary source of phosphorus?

<p>Leafy greens (C)</p> Signup and view all the answers

What is the primary function of the kidney in calcium and phosphate homeostasis?

<p>Modulation of calcium and phosphate excretion. (D)</p> Signup and view all the answers

Which form of Vitamin D is the active hormone that regulates calcium and phosphate levels?

<p>Calcitriol (A)</p> Signup and view all the answers

What stimulates the formation of active vitamin D in the kidneys?

<p>Parathyroid hormone (C)</p> Signup and view all the answers

What is the absorption efficiency of phosphate in the small intestine?

<p>65% (C)</p> Signup and view all the answers

What role does bone play in calcium and phosphate homeostasis?

<p>It acts as an alternate source of calcium and phosphate. (A)</p> Signup and view all the answers

Which hormone is NOT directly involved in maintaining calcium and phosphate homeostasis?

<p>Insulin (B)</p> Signup and view all the answers

What is the approximate normal plasma level of calcium in mg/dL?

<p>9.5 - 10.5 mg/dL (D)</p> Signup and view all the answers

Which form of plasma calcium is considered the biologically active form?

<p>Free ionized Ca+2 (B)</p> Signup and view all the answers

What is the primary site for calcium absorption?

<p>Duodenum (B)</p> Signup and view all the answers

What factors can influence the levels of free ionized Ca+2 in the plasma?

<p>Plasma proteins, pH, and electrolytes (B)</p> Signup and view all the answers

What is the daily calcium requirement for adults to maintain balance?

<p>1-1.5 g (B)</p> Signup and view all the answers

What enhances active calcium transport in the gut?

<p>Vitamin D (A)</p> Signup and view all the answers

What is the impact of high levels of Ca2+ on the production of active vitamin D?

<p>Decreases the formation of 1,25-dihydroxycholecalciferol (C)</p> Signup and view all the answers

Which of the following can lead to vitamin D deficiency?

<p>Fat malabsorption (C)</p> Signup and view all the answers

What is the primary effect of calcitriol on bone health?

<p>Promotes osteoblast activity and osteoclast formation (C)</p> Signup and view all the answers

What role does magnesium play in PTH secretion?

<p>Is required for normal PTH secretion (B)</p> Signup and view all the answers

How does PTH affect calcium and phosphate levels in the body?

<p>Increases both calcium and phosphate levels (C)</p> Signup and view all the answers

What can result from a deficiency of vitamin D?

<p>Hypocalcemia and hypophosphatemia (B)</p> Signup and view all the answers

What is the main trigger for the release of PTH?

<p>Hypocalcemia (C)</p> Signup and view all the answers

What is the effect of active vitamin D on PTH secretion?

<p>Inhibits PTH formation (C)</p> Signup and view all the answers

What is the primary effect of parathyroid hormone (PTH) on bone?

<p>Promotes bone resorption (C)</p> Signup and view all the answers

Which of the following is a significant symptom of hypoparathyroidism?

<p>Hypocalcemic tetany (D)</p> Signup and view all the answers

What is a characteristic sign of hypocalcemia?

<p>Trousseau’s sign (A)</p> Signup and view all the answers

What can result from chronic low plasma calcium levels?

<p>Secondary hyperparathyroidism (A)</p> Signup and view all the answers

Which condition can lead to hypercalcemia?

<p>Excess PTH activity (D)</p> Signup and view all the answers

Which of the following is NOT a common symptom of hyperparathyroidism?

<p>Increased appetite (D)</p> Signup and view all the answers

Which of these complications can occur due to hypercalcemia?

<p>Kidney stones (B)</p> Signup and view all the answers

What role does parathyroid hormone have on renal function?

<p>Increases calcium re-absorption (A)</p> Signup and view all the answers

Flashcards

Calcium Homeostasis

The process of maintaining a stable level of calcium in the body.

Calcium Absorption (Gut)

Taking calcium from food into the bloodstream through the intestines.

Bone's role in calcium

Storing and releasing calcium as needed to maintain blood calcium levels.

Kidney and calcium

Regulates calcium excretion, removing excess calcium from the blood.

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Parathyroid Hormone (PTH)

Hormone that increases calcium levels in the blood.

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Vitamin D's role in calcium

Increases calcium absorption from the gut, and regulates calcium balance.

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Plasma Calcium levels

The amount of calcium circulating in the blood, crucial for bodily function.

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Calcium Function in Body

Crucial for bone & teeth, blood clotting, nerve/muscle function & enzyme activation.

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Calcium absorption factors

Factors affecting calcium absorption from the intestines include pH, diet type, and hormones.

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Calcium kidney handling

Kidneys reabsorb most filtered calcium (98-99%) through active and passive transport in nephrons.

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Vitamin D's role in Ca2+

Vitamin D increases active calcium absorption and is crucial to calcium regulation.

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Factors that inhibit calcium absorption

High phosphorus, phytates, oxalates, and lack of stomach acidity negatively affect calcium absorption.

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Calcium regulation hormones

Vitamin D, parathyroid hormone (PTH), and calcitonin control calcium levels in the body.

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Hypocalcemia effect

Low calcium levels increase neuronal membrane permeability to sodium, causing neuronal hyper-excitability.

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Phosphate body distribution

Most phosphate is in bones, followed by cells; only a small part is in the extracellular fluid.

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Phosphate functions

Phosphate is vital for bone and teeth formation, as well as cellular structure and function.

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Phosphate Absorption

The process of taking phosphate from food into the bloodstream, primarily through the small intestine.

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Vitamin D's role (phosphate)

Vitamin D stimulates phosphate absorption in the intestines, specifically in the duodenum and jejunum.

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PTH and Phosphate

Parathyroid hormone (PTH) regulates phosphate reabsorption in the kidneys, reabsorbing 85-90%. It inhibits a specific protein called NaPi-IIa.

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Calcium & Phosphate Link

Calcium and phosphate homeostasis are interconnected. Their levels influence each other.

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Active Vitamin D3

1,25-dihydroxycholecalciferol (calcitriol), the biologically active form of vitamin D3, crucial for calcium regulation.

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Vitamin D3 source

Vitamin D3 is produced in the skin from cholesterol in response to sunlight or ingested in some foods, especially fish.

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Vitamin D2 source

Vitamin D2 is primarily obtained through plant sources, fortified foods and animal products.

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Vitamin-D kidney process

Vitamin D is modified in the liver and then kidneys to become biologically active 1,25-dihydroxyvitamin D3 (calcitriol).

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Vitamin D's role in calcium regulation

Vitamin D increases calcium absorption in the gut, reabsorption in the kidneys, and stimulates bone remodeling.

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PTH's role in calcium homeostasis

Parathyroid hormone (PTH) raises blood calcium levels by targeting bones, kidneys, and intestines.

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Negative feedback in Calcium regulation

High serum calcium levels suppress PTH production while low levels stimulate it.

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Vitamin D activation and form

Inactive vitamin D is converted to its active form, calcitriol in the kidneys to support calcium regulation.

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FGF 23's impact on calcium

Fibroblast growth factor 23 (FGF23) acts to lower phosphate levels and indirectly affects Vitamin D activation; inhibiting calcium absorption.

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Hypocalcemia's cause

Low blood calcium (hypocalcemia) can be caused by vitamin D deficiency, impaired PTH function or magnesium deficiency.

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PTH's Inhibition by Vitamin D

Active Vitamin D directly inhibits the formation and release of PTH.

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Kidney's calcium role in homeostasis

Kidneys play a crucial role in the regulation of calcium absorption and excretion in the blood.

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PTH's effect on bone

PTH stimulates osteoclasts, increasing bone resorption and releasing calcium and phosphate into the blood.

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PTH's effect on kidney (phosphate)

PTH reduces phosphate reabsorption in the kidneys, leading to more phosphate excretion.

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Hypocalcemia symptoms

Low blood calcium can lead to muscle spasms (tetany), facial muscle twitching, and potentially life-threatening airway obstruction.

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Hypercalcemia cause (malignancy)

Cancer in the bones can cause high calcium levels by releasing calcium into the blood, or a cancer can secrete a protein that acts like PTH.

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Hyperparathyroidism symptom (mild)

Mild symptoms like loss of appetite, fatigue, and personality changes can occur due to excess PTH.

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Secondary hyperparathyroidism

Low blood calcium chronically stimulates the parathyroid glands to increase their size.

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Hypercalcemia consequence (kidneys)

High calcium levels can lead to kidney stones due to excess calcium and phosphate in the urine.

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Hypercalcemia Symptoms

High blood calcium can cause things like nervous system depression, muscle weakness, and heart problems.

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Study Notes

Mineral Homeostasis

  • Mineral homeostasis is the process of maintaining the balance of minerals, especially calcium and phosphate, in the body.
  • Calcium is vital for bone and teeth formation, blood clotting, nerve and muscle function, and many enzymatic processes.
  • The body contains about 1100 grams of calcium in adults.
  • About 99% of calcium is stored in bones and teeth.
  • Normal plasma calcium levels are approximately 9.5 mg/dL (8.5-10.5), or 2.4 mmol/L.
  • Calcium in the blood exists in three forms: 50% ionized, 41% protein-bound, and 9% complexed.
  • The daily calcium requirement for adults is about 1-1.5 g (25 mmol).
  • Calcium is absorbed primarily in the duodenum and proximal jejunum. Mechanisms include passive diffusion (for adequate intake) and active transport (vitamin D).
  • Factors affecting calcium absorption include pH (acidity enhances), diet type (protein and sugars increase absorption; fats, phosphates, oxalates, and phytates decrease), and hormones (Vitamin D and growth hormone increase).
  • Calcium's primary control sites are the gastrointestinal tract, bones, and kidneys.
  • The kidneys filter about 10,000 mg of Ca2+ daily, with 98-99% reabsorbed actively or passively.
  • This reabsorption is influenced by vitamin D in proximal tubules and controlled by PTH in distal tubules.
  • The importance of Calcium regulated by three hormones: Vitamin D, parathyroid hormone, & calcitonin.

Regulation of Mineral Homeostasis

  • Calcium homeostasis is regulated tightly by parathyroid hormone (PTH), vitamin D, and calcitonin.
  • The three hormones work together to maintain calcium and phosphate levels.

Phosphate Homeostasis

  • Phosphate is the second most abundant mineral in the body (500-800 grams). It's important for bone formation, energy transfer, acid-base balance, and cell structure/function.
  • About 85-90% of total body phosphate is found in bones as hydroxyapatite.
  • Plasma phosphate levels are about 12 mg/dL, predominantly as inorganic phosphate (PO4-3, HPO4-2, and H2PO4-).
  • Phosphate is readily available from foods, absorbed efficiently (65%), and found in meat, fish, eggs, and dairy products.
  • Vitamin D is involved in stimulating active phosphate absorption.
  • High calcium intake can inhibit phosphate absorption.
  • Phosphate absorption in kidneys is about 85-90%.

Vitamin D

  • Vitamin D is a steroid hormone vital for calcium/phosphate homeostasis.
  • The main forms are Vitamin D2 (ergocalciferol) obtained from plants, and Vitamin D3 (cholecalciferol) produced in skin by sunlight or consumed in food.
  • Active Vitamin D3 plays crucial roles in calcium/phosphate absorption.

Calcium Regulation by Hormones

  • Parathyroid Hormone (PTH)

    • Main function is to increase blood calcium by promoting bone resorption, increasing calcium reabsorption in the kidneys, and stimulating vitamin D synthesis.

  • Active Vitamin D (1,25-(OH)2D):

    • Primary function is to increase intestinal calcium and phosphate absorption.

  • Calcitonin:

    • Primarily decreases blood calcium and phosphate levels by inhibiting bone resorption.

Effects of PTH (Parathyroid Hormone)

  • PTH stimulates bone osteoclast activity, releasing calcium and phosphate into the bloodstream.
  • Kidneys reabsorb more calcium, excreting more phosphate.
  • Increases active vitamin D formation.

Hypoparathyroidism

  • This condition is characterized by insufficient PTH, leading to critically low blood calcium. This severely affects nerve/muscle excitability.

Hyperparathyroidism

  • High PTH conditions can be caused by parathyroid tumors or chronic kidney disease marked by abnormally high blood calcium.

Hypercalcemia

  • High calcium levels in the blood can result from various issues, including hyperparathyroidism, high vitamin D levels, or cancers that cause bone breakdown.
  •   Symptoms potentially include progressively worsening nervous system depression, weakness, constipation, cardiac arrhythmias, and the formation of kidney stones.

Calcitonin

  • Calcitonin is a hormone that lowers blood calcium levels primarily by inhibiting bone resorption.
  • It's primarily secreted by the thyroid gland, in response to increasing blood calcium levels.

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Mineral Homeostasis (2024-2025) MSKS-321 PDF

Description

Test your knowledge on mineral homeostasis, focusing on calcium and phosphate balance in the human body. This quiz covers the physiological roles of calcium, its absorption mechanisms, and factors influencing its levels. Perfect for students studying human physiology or health sciences.

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