Chapter 21 |Hormonal Control of Calcium

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What is the role of plasma proteins in binding with Ca2+?

They inhibit Ca2+ binding

They are less ionized at high pH

They are more ionized at high pH (correct)

They have no impact on Ca2+ binding

How much Ca2+ is exchanged between plasma and the stable pool of bone calcium per day?

1000 mmol

500 mmol

7.5 mmol (correct)

50 mmol

What regulates the distal tubular reabsorption of Ca2+ in the kidneys?

Brush border cells

Proximal tubules

PTH (correct)

Plasma proteins

How much of the filtered Ca2+ in the kidneys is reabsorbed?

98-99% Signup and view all the answers

What is the active form of vitamin D that is also called calcitriol?

1,25-dihydroxycholecalciferol Signup and view all the answers

How is vitamin D3 mainly produced in mammals?

By the action of ultraviolet light on 7-dehydrocholesterol Signup and view all the answers

Where does the conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol mainly occur?

In the proximal tubules of the kidneys Signup and view all the answers

Which protein transports vitamin D3 and its hydroxylated derivatives in the plasma?

Vitamin Dbinding protein (DBP) Signup and view all the answers

Which form of calcium is a vital second messenger in the body fluids?

Ionized calcium (Ca2+) Signup and view all the answers

What is the consequence of a decrease in extracellular Ca2+ in vivo?

Hypocalcemic tetany Signup and view all the answers

Why is it important to know the plasma protein level when evaluating total plasma calcium?

To understand the extent of Ca2+ binding by plasma proteins Signup and view all the answers

How do symptoms of tetany vary with changes in total calcium levels?

Increased total calcium levels worsen tetany symptoms Signup and view all the answers

Which compounds in the body contain phosphate?

ATP, cyclic adenosine monophosphate (cAMP), and many proteins Signup and view all the answers

Where is 85-90% of the total body phosphorus found?

In the skeleton Signup and view all the answers

How much phosphorus normally enters bone per kg per day?

3 mg Signup and view all the answers

What is the main site of Pi reabsorption in the kidney involving sodium-dependent Pi cotransporters?

Proximal tubule Signup and view all the answers

What is the primary action of parathyroid hormone (PTH) in calcium homeostasis?

Mobilize calcium from bone Signup and view all the answers

Which hormone is derived from vitamin D and plays a significant role in calcium homeostasis?

1,25-Dihydroxycholecalciferol Signup and view all the answers

What is the main function of calcitonin in calcium metabolism?

Inhibit bone resorption Signup and view all the answers

Which organs or tissues respond to changes in extracellular calcium concentrations by mobilizing, excreting, or taking up calcium?

Kidneys, bones, intestine Signup and view all the answers

What stimulates calcitonin secretion in the body?

Gastrin Signup and view all the answers

Where are the receptors for calcitonin found in the body?

Bones and kidneys Signup and view all the answers

What is the primary source of calcitonin in mammals?

Thyroid gland Signup and view all the answers

In which syndrome is the plasma calcitonin level elevated?

Zollinger–Ellison syndrome Signup and view all the answers

What is the primary function of phosphorylation and dephosphorylation of proteins in the body?

To regulate cell function Signup and view all the answers

Where is the majority of filtered Pi reabsorbed in the kidneys?

Proximal tubule Signup and view all the answers

What happens to NaPi-IIa when it is inhibited by PTH?

It undergoes internalization and degradation Signup and view all the answers

Which process is stimulated by many factors that also increase Ca2+ absorption?

Pi absorption Signup and view all the answers

Which cells are responsible for bone formation?

Osteoblasts Signup and view all the answers

What contributes to the differentiation of osteoblasts?

Extensive growth factor regulation Signup and view all the answers

How do osteoclasts attach to bone?

Via integrins in a sealing zone Signup and view all the answers

What is the function of the periosteum?

Site of ligament attachment Signup and view all the answers

What happens to the cartilage cells at the end of long bone growth during epiphysial closure?

They secrete vascular endothelial growth factor (VEGF) Signup and view all the answers

Which hormone has the most significant impact on the width of the epiphysial plate?

Insulin-like Growth Factor I (IGF-I) Signup and view all the answers

What leads to the closure of the epiphyses in bones?

Hypertrophy of cartilage cells Signup and view all the answers

How is the 'bone age' of a young individual typically determined?

By radiographing the skeleton Signup and view all the answers

Which hormone is responsible for orderly temporal sequence closure of the epiphyses after puberty?

Growth hormone Signup and view all the answers

What is the primary function of the periosteum in relation to bone structure?

Covering and nourishing bone surfaces Signup and view all the answers

How does linear bone growth continue until epiphysial closure?

By new bone formation at the shaft ends Signup and view all the answers

What is the role of Vascular Endothelial Growth Factor (VEGF) in bone development and maturation?

It leads to vascularization and ossification Signup and view all the answers

What is determined by radiographing a young individual's skeleton in relation to bone health?

The 'bone age' based on open or closed epiphyses Signup and view all the answers

Proton pumps acidify the area to approximately pH 7.0.

False Signup and view all the answers

Pyridinolines can be measured in the urine as an index of bone resorption rate.

True Signup and view all the answers

Bone turnover rate is higher in infants than in adults.