week 5 Flashcards
What are the three main functions of calcium in the body?
Structural function (bones & teeth), neurotransmitter release, and muscle contraction.
Structural function (bones & teeth), neurotransmitter release, and muscle contraction.
Free ionized calcium (47%), calcium bound to plasma proteins (46%), and non-ionized calcium salts (7%)
What hormone is responsible for increasing calcium levels in the blood?
PTH
What is the role of calcitonin in calcium homeostasis?
It lowers plasma calcium by inhibiting osteoclastic bone resorption.
How is vitamin D activated in the body?
Through two hydroxylation steps—first in the liver to form 25-hydroxyvitamin D3, then in the kidney to form the active 1,25-dihydroxyvitamin D3 (calcitriol)
What are the symptoms of hypercalcemia?
Kidney stones, depressed neuromuscular excitability, constipation, and cardiac arrhythmias.
What are the common causes of hypocalcemia?
Vitamin D deficiency, hypoparathyroidism, renal failure, and magnesium deficiency.
What are the three main hormones regulating calcium homeostasis?
What are the three main hormones regulating calcium homeostasis?
How does PTH regulate calcium levels?
It increases bone resorption, enhances calcium reabsorption in the kidneys, and stimulates the production of calcitriol to promote calcium absorption in the intestines.
What are the three main types of bone cells?
Osteoclasts (bone resorption), osteoblasts (bone formation), and osteocytes (mature bone cells).
What is the main effect of calcitonin on bone?
It inhibits osteoclast activity, reducing bone resorption and lowering plasma calcium levels.
How does phosphate contribute to the body’s function?
It plays a role in bone mineralization, buffering systems, DNA/RNA structure, cell membranes, and ATP production.
What are common causes of hyperphosphatemia?
Renal failure, hyperparathyroidism, and excessive phosphate intake.
What are the main roles of magnesium in the body?
Bone mineralization, enzyme activation, nerve impulse transmission, and muscle function.
What condition is characterized by excessive osteoclastic activity leading to deformed bones?
Paget’s disease
What biochemical markers indicate bone formation?
Serum alkaline phosphatase (ALP), bone-specific alkaline phosphatase (BAP), and osteocalcin.
What is the function of the calcium-sensing receptor in the parathyroid gland?
It detects changes in plasma calcium levels and regulates PTH secretion accordingly.
How does PTH affect phosphate levels?
It decreases phosphate reabsorption in the kidneys, leading to increased phosphate excretion (phosphaturia).
What enzyme is responsible for converting 25(OH)D₃ to active 1,25(OH)₂D₃ in the kidneys?
1α-hydroxylase.
What is the major cause of secondary hyperparathyroidism?
Chronic kidney disease or vitamin D deficiency
What condition is characterized by vitamin D deficiency leading to defective bone mineralization?
Rickets in children and osteomalacia in adults.
What role does magnesium play in calcium homeostasis?
It is necessary for PTH secretion and calcium transport in the body.
What hormone inhibits osteoclast activity and reduces bone resorption?
Calcitonin
How does chronic kidney disease affect phosphate levels?
It reduces phosphate excretion, leading to hyperphosphatemia.
What is the recommended treatment for severe hypercalcemia (>3.5 mmol/L)?
Dialysis or parathyroidectomy.
What is the main effect of vitamin D on the intestines?
It increases calcium and phosphate absorption.
What condition is caused by excessive bone turnover with disorganized bone formation?
Paget’s disease
What is the effect of vitamin D supplementation in elderly individuals?
It reduces the risk of fractures and bone loss
What is the definition of a lipid?
Lipids are organic molecules that are insoluble in water and function as energy stores, membrane components, steroid hormones, and fat-soluble vitamins.
What are the four main classes of lipids?
Triglycerides, phospholipids, cholesterol, and fatty acids.
What is the primary role of triglycerides?
They serve as the main dietary fat, an energy store, and a component of cell membranes.
What is cholesterol used for in the body?
It is important for membrane structure and fluidity, is a precursor of steroid hormones (e.g., cortisol, estrogen, testosterone), and is involved in the synthesis of vitamin D and bile acids.
Why do lipids need transport systems in the body?
Lipids are not water-soluble, so they must be transported in association with proteins, mainly through lipoproteins.
What is the primary function of LDL?
LDL is the main carrier of cholesterol and delivers it to tissues. Excess LDL contributes to atherosclerosis.
What is the role of HDL in lipid metabolism?
HDL helps remove cholesterol from tissues and transports it to the liver for excretion, playing a protective role against cardiovascular disease.
What is hyperlipidemia?
A condition characterized by elevated levels of lipids (cholesterol or triglycerides) in the blood, which can increase the risk of cardiovascular disease.
What is the primary treatment approach for hyperlipidemia?
Lifestyle changes (healthy diet, exercise, weight management, quitting smoking) and medications like statins or fibrates if necessary.
How do statins work?
Statins inhibit HMG-CoA reductase, reducing cholesterol synthesis, increasing LDL receptor expression, and lowering LDL levels.
What is the relationship between elevated plasma lipids and cardiovascular disease (CVD)?
Elevated plasma lipids contribute to atherosclerosis
What are the major apoproteins, and what are their roles?
ApoA: Found in HDL, helps remove cholesterol from tissues.
ApoB: Found in LDL, VLDL, and chylomicrons, aids in lipid transport.
ApoC: Regulates lipoprotein lipase activity.
ApoE: Important for the clearance of lipoprotein remnants by the liver.
What is the function of apoproteins in lipoproteins?
Apoproteins provide structural support and regulate lipoprotein metabolism by interacting with enzymes and receptors.
What is Lecithin-Cholesterol Acyltransferase (LCAT), and what does it do?
LCAT is an enzyme that converts cholesterol into cholesterol esters, facilitating cholesterol transport by HDL.
How does LDL contribute to atherosclerosis?
LDL can penetrate blood vessel walls and be taken up by macrophages, forming foam cells that contribute to plaque formation.
Hypercholesterolemia (FH)?
A genetic disorder characterized by high cholesterol levels due to defective or absent LDL receptors, increasing CHD risk.
How does Familial Hypertriglyceridemia differ from FH?
It is characterized by high triglyceride levels due to excess VLDL production rather than defective LDL receptors.
What are fibrates, and how do they work?
Fibrates stimulate lipoprotein lipase, reducing triglycerides and increasing HDL levels
