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</p> Signup and view all the answers

    What dietary component decreases calcium absorption?

    <p>Fats</p> Signup and view all the answers

    Which hormone decreases when there is hypercalcemia?

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

    What is the primary role of phosphate in the body?

    <p>Formation of bones and teeth</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</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.</p> Signup and view all the answers

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

    <p>Cholecalciferol</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.</p> Signup and view all the answers

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

    <p>Leafy greens</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.</p> Signup and view all the answers

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

    <p>Calcitriol</p> Signup and view all the answers

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

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

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

    <p>65%</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.</p> Signup and view all the answers

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

    <p>Insulin</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</p> Signup and view all the answers

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

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

    What is the primary site for calcium absorption?

    <p>Duodenum</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</p> Signup and view all the answers

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

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

    What enhances active calcium transport in the gut?

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

    Which of the following can lead to vitamin D deficiency?

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

    What is the primary effect of calcitriol on bone health?

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

    What role does magnesium play in PTH secretion?

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

    What can result from a deficiency of vitamin D?

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

    What is the main trigger for the release of PTH?

    <p>Hypocalcemia</p> Signup and view all the answers

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

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

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

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

    Which of the following is a significant symptom of hypoparathyroidism?

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

    What is a characteristic sign of hypocalcemia?

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

    What can result from chronic low plasma calcium levels?

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

    Which condition can lead to hypercalcemia?

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

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

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

    Which of these complications can occur due to hypercalcemia?

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

    What role does parathyroid hormone have on renal function?

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

    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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