29 Questions
Which of the following hormones plays a minor role in maintaining calcium concentration in the extracellular fluid?
Calcitonin
What percentage of calcium in the plasma is present in the ionized form?
50%
What is the total weight of parathyroid tissue in the human body?
150 mg
What is the primary function of calcium in the development of bone and teeth?
Structural function
How many amino acids are present in the intact PTH molecule?
84 amino acids
What is the half-life of intact PTH in the blood?
3-4 minutes
What percentage of protein-bound calcium is bound to albumin?
80%
What is the term for the mechanism by which the body maintains adequate calcium levels?
Calcium homeostasis
Which part of the PTH molecule is necessary for PTH receptor binding in target cells?
N-terminal 1-34 amino acid sequence
What is the primary function of parathyroid hormone (PTH) in the body?
Acute regulation of plasma calcium levels
What is the role of calcium in the transmission of nerve impulses?
Neuromuscular function
What is the consequence of derangements in calcium metabolism?
Either hypercalcemia or hypocalcemia
What is the primary effect of PTH on osteoclasts?
Stimulating their development
What is the primary role of 25-hydoxylase in vitamin D metabolism?
Converting cholecalciferol to calcidiol
What is the net result of PTH's actions on bone and calcium levels?
Increased plasma calcium levels
Where is the 1α-hydroxylase enzyme located?
Proximal convoluted tubules of the nephrons
What is the role of vitamin D-binding protein in vitamin D metabolism?
Transporting vitamin D
What is the effect of PTH on osteoblast activity?
Slowly stimulating osteoblast activity
What is the effect of 1:25-DHCC on 25-HCC?
It stimulates the conversion of 25-HCC to 24:25-DHCC
What is the effect of PTH on 1α-hydroxylase activity?
It directly stimulates the activity
What is the role of calbindin-D in the intestine?
It promotes the absorption of calcium and phosphate from the gut lumen
What is the effect of calcitriol on bone mobilization?
It stimulates bone mobilization
What is the role of osteocalcin in bone formation?
It is a marker of bone formation and turnover
What is the effect of calcitriol on alkaline phosphatase production?
It stimulates the production of alkaline phosphatase
What is the primary stimulus for PTH release in secondary hyperparathyroidism?
Hypocalcaemia
What is the result of end-organ resistance to parathyroid hormone in secondary hyperparathyroidism?
Decreased mobilization of calcium from the bones
What is the effect of increased intracellular phosphate on the 1-hydroxylase enzyme in end-stage renal failure?
It inhibits the activity of the 1-hydroxylase enzyme
What is the result of reduced normal renal tissue in end-stage renal failure?
Reduced capacity for 1:25-DHCC synthesis
What is the consequence of hypocalcaemia in end-stage renal failure?
Increased release of PTH
This quiz covers the basics of calcium metabolism, including its functions, hormones that regulate it, and vitamin D production and metabolism. It's an overview of calcium homeostasis, the balance between intake and output, and its movement between different bodily systems.
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