89 Questions
What is the primary mechanism of calcium absorption in the small intestine?
Active transport via calcium-binding protein
What is the primary function of 1,25-dihydroxyvitamin D in calcium homeostasis?
Regulation of intestinal calcium absorption
What is the primary effect of PTH on osteoclasts?
Stimulation of osteoclast activity
Which hormone plays a major role in regulating bone formation and resorption?
PTH
What is the primary function of calcitonin in calcium homeostasis?
Inhibition of osteoclast activity
Which of the following is a consequence of hypocalcemia?
All of the above
What is the primary stimulus for calcitonin secretion from parafollicular cells in the thyroid gland?
Increased plasma Ca2+ concentration
What is the effect of parathyroid hormone on phosphate reabsorption in the kidney?
It inhibits phosphate reabsorption
What is the role of vitamin D in intestinal calcium absorption?
Vitamin D stimulates calcium absorption in the small intestine
What is the effect of calcitonin on osteoclastic bone resorption?
It inhibits osteoclastic bone resorption
What is the effect of PTH on bone metabolism?
It promotes bone resorption
What is the relationship between calcitonin and PTH in terms of their effects on bone metabolism?
They have antagonistic effects on bone metabolism
What is the primary function of 1,25-dihydroxycholecalciferol in the small intestine?
To increase the expression of calcium-binding proteins
What is the effect of increased circulating levels of PTH on 1α-hydroxylase activity?
It increases 1α-hydroxylase activity
What is the primary role of vitamin D in bone metabolism?
To stimulate osteoclast activity and promote bone resorption
What is the consequence of vitamin D deficiency in children?
Rickets
What is the effect of 1,25-dihydroxycholecalciferol on phosphate reabsorption in the kidney?
It stimulates phosphate reabsorption
What is the stimulus for the production of the active metabolite of vitamin D in the kidney?
Low dietary intake of calcium
In which cell type does PTH bind to stimulate bone resorption?
Osteoblasts
What is the effect of PTH on osteoblast activity?
PTH increases osteoblast activity
What is the primary role of vitamin D in bone metabolism?
Vitamin D increases calcium absorption in the intestine
What is the consequence of PTH-mediated bone resorption?
Release of calcium ions from the bone matrix
What is the indirect mechanism by which PTH stimulates bone resorption?
PTH induces the release of IL-6 and RANK ligand from osteoblasts
In which tissue does PTH stimulate the activation of vitamin D?
Kidney
What is the effect of decreased plasma Ca2+ concentration on 1α-hydroxylase activity?
It increases the activity of 1α-hydroxylase enzyme.
What is the role of vitamin D in bone mineralization?
It increases plasma levels of both Ca2+ and phosphate to promote mineralization of new bone.
What is the consequence of vitamin D deficiency in adults?
Osteomalacia, a condition in which new bone fails to mineralize, resulting in bending and softening of the weight-bearing bones.
What is the role of osteoblasts in bone remodeling?
They deposit new bone tissue, increasing bone mass.
What is the effect of 1,25-dihydroxycholecalciferol on calcium absorption in the small intestine?
It stimulates the formation of calcium-binding proteins, promoting calcium absorption.
What is the role of 1,25-dihydroxycholecalciferol in bone mineralization?
It promotes bone mineralization by stimulating osteoblast activity.
What is the effect of PTH on phosphate reabsorption in the proximal convoluted tubule of the nephron?
Inhibition of phosphate reabsorption
What is the role of 1,25-dihydroxycholecalciferol in the small intestine?
It stimulates calcium absorption in the small intestine
What is the effect of PTH on bone metabolism?
It stimulates osteoclast activity and bone resorption
What is the consequence of vitamin D deficiency in children?
Rickets
What is the role of PTH in regulating vitamin D synthesis?
It stimulates vitamin D synthesis
What is the effect of vitamin D deficiency on bone metabolism?
It leads to a decrease in osteoblast activity and bone formation
What is the effect of increased circulating levels of PTH on 1α-hydroxylase enzyme activity?
Stimulation of the enzyme
Which of the following is the primary site of vitamin D synthesis?
Skin and kidney
What is the role of vitamin D in bone mineralization?
Increase in both calcium and phosphate concentrations
What is the effect of PTH on vitamin D synthesis?
Stimulation of vitamin D synthesis
What is the role of vitamin D in the small intestine?
Increase in both calcium and phosphate absorption
What is the primary function of vitamin D in conjunction with PTH?
Regulation of both calcium and phosphate concentrations
What is the primary stimulator of the 1α-hydroxylase enzyme activity?
Decreased plasma calcium concentration
What is the primary purpose of the regulation of vitamin D synthesis?
To regulate plasma calcium levels
What is the primary role of vitamin D in bone mineralization?
To promote mineralization of new bone
What is the effect of vitamin D on osteoclast activity?
It increases osteoclast activity
What is the consequence of vitamin D deficiency in children?
Rickets
What is the effect of 1,25-dihydroxycholecalciferol on calcium absorption in the small intestine?
It increases calcium absorption
What stimulates the activity of the 1α-hydroxylase enzyme in the kidney?
Increase in parathyroid hormone levels
What is the primary stimulus for the synthesis of 1,25-dihydroxycholecalciferol in the kidney?
Decreased calcium levels
What is the role of 1,25-dihydroxycholecalciferol in bone mineralization?
Regulating calcium and phosphate metabolism
What is the primary site of vitamin D synthesis?
Skin
What is the function of the 25-hydroxycholecalciferol-binding protein in plasma?
Transporting vitamin D metabolites
What is the effect of decreased calcium levels on vitamin D synthesis?
Stimulating parathyroid hormone production
What is the primary consequence of failing to comply with a medically prescribed steroid taper?
Addisonian crisis
What is the primary source of excess cortisol in Cushing's syndrome?
Adrenal gland tumor
What are the common symptoms of both Cushing's disease and Cushing's syndrome?
All of the above
What is the primary cause of Cushing's disease?
Pituitary adenoma
What is the primary difference between Cushing's disease and Cushing's syndrome?
The source of excess cortisol
What is the primary mechanism of Adrenal Insufficiency in Addison's Disease?
Autoimmune destruction of adrenal cortex
What is the characteristic feature of Primary Hypercortisolism (Cushing's Syndrome)?
Low ACTH levels and adrenal gland tumor
What is the most common cause of Secondary Hypercortisolism (Cushing's Disease)?
Pituitary tumor
What is the hallmark of Iatrogenic Cushing's Syndrome?
High Cortisol levels and low ACTH levels
What is the threshold of adrenal cortex destruction required for Adrenal Insufficiency to occur?
At least 90% of the adrenal cortex
What is the characteristic feature of Secondary Adrenal Insufficiency (Hypopituitarism)?
Low ACTH and low cortisol levels
What is the primary symptom of adrenal insufficiency in women?
Decreased libido and pubic hair
What is the cause of secondary adrenal insufficiency?
Lack of ACTH
What is the effect of Addison's disease on cortisol levels?
Decreased cortisol levels
What is the treatment for Addison's disease?
Replacement of glucocorticoids and mineralocorticoids
What is the effect of Addison's disease on pubic and axillary hair in women?
Decreased hair growth
What is the cause of hyperkalemia in Addison's disease?
Decreased aldosterone levels
What is a consequence of chronic stress on the cardiovascular system?
Left ventricular hypertrophy
What is the primary mechanism by which chronic stress impairs immune function?
Impaired immune surveillance
Which of the following is a consequence of chronic stress on metabolism?
Decreased glucose tolerance
What is the primary effect of glucocorticoids on metabolism during chronic stress?
Increased gluconeogenesis
What is the primary consequence of chronic stress on the central nervous system?
Impaired judgement and impulse control
What is the primary effect of chronic stress on behavior?
Increased irritability and hostility
What is the term used to describe the state of balance and stability in an organism?
Homeostasis
Who is credited with the discovery of the 'fight or flight' response?
Walter Cannon
What is the term used to describe the deviation from a normal or steady state?
Stress
What is the name of the scientist who demonstrated that stress can alter an organism's resistance to disease?
Louis Pasteur
What is the term used to describe the system-wide arousal of the body in response to physical or psychological danger?
Fight or flight response
Who is credited with the discovery that stress can cause diseases?
Galen
What is associated with negative feelings and disturbed bodily states?
Distress
What is the effect of chronic GC exposure on adipose tissue function and lipid metabolism?
Promotes insulin resistance
What determines individual differences in stress sensitivity?
All of the above
What is the effect of chronic stress on the HPA axis?
Enhanced susceptibility to activation
What is associated with positive feelings and healthy bodily states?
Eustress
What is the effect of cortisol on insulin resistance?
Promotes insulin resistance
This quiz covers the mechanisms of maintaining homeostasis of body calcium and phosphate concentrations, body stores of calcium, and the hormones and factors that regulate calcium and phosphate homeostasis.
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