Chedy - theme 14 Flashcards
What organ controls ion balance?
Adrenal medulla
Hormones involved in ion control:
Aldosterone, vasopressin, and ANP
ANP: what is it
Atrial natriuretic peptide, from the heart.
Hypothalamic osmoregulators:
Decrease in blood osmolarity results in increased ADH production from post pit gland, makes the kidney take up water from urine, inhibiting aldosterone secretion causing elimination of Na and production of K, and increased ANP to decrease Na uptake.
Mineralocorticoids:
Regulates salt and water by causing the kidneys to actively take up Na+ and passively take up water, active secretion of K+ into the collecting tubule, active secretion of H+ via ATPases into the collecting tubule. Regulated by levels of K+ and angiotensin II. Increase blood pressure and volume.
Aldosterone:
Increases Na+ reabsorption from kidney. When osmolarity is high, aldosterone is inhibited and Na+ is eliminated.
ANP: what it do
Decreases Na+ reabsorption in response to high Na+
ANP vs aldosterone seesaw:
Aldosterone wants Na+ uptake, ANP wants to kick it out. When aldosterone is high, ANP is low, and vice versa.
What vitamin is needed for keeping calcium?
Active form of vit D
Rickets:
Deformation of weight-bearing bones (legs). Caused by low vit D, phosphorous, and/or calcium at young age.
Osteoporosis:
Mineral and organic components of bone are reduced, wrecking the balance between bone formation and breakdown.
Functions of bone:
Support and protection, production of red and white blood cells, production and storage of hormones, storage of minerals.
Inorganic composition of bones:
Carbonated hydroxyapatite, Ca10(PO4)6(OH)2, on a protein matrix called osteoid.
Bones as endocrine organs:
Stores growth factors (IGF, transforming growth factor, bone morphogenetic proteins)
Secretes fibroblast growth factor (FGF-23), which reduces phosphate reabsorption in kidneys
Secretes osteocalcin, which contributes to the regulation of glucose and fat levels by increasing insulin secretion and sensitivity and by boosting the number of insulin-producing cells and reducing fat stores.
Metabolic function of bones:
Mineral storage, fat storage, acid-base balance (buffers by absorbing/releasing alkaline salts), detox (collecting metals for slow excretion)
Cellular structure of bone:
Osteoblasts and osteoclasts
Osteoblasts:
Bone-forming cells that become osteocytes. Osteocytes can produce osteoid, which mineralizes into bone. They also produce alkaline phosphatase, a major enzyme in mineralization.
Osteoclasts:
Bone resorption: digests mineralized bone protein with acid phosphatase and collagenase. Regulate blood calcium level.
Endocrine control of bone cell activity:
Mostly PTH and calcitonin, also some vit D and FGF-23 up in there
PTH: how it regulates Ca2+
To increase calcium:
Increases Ca2+ absorption by reducing the Ca2+ that gets peed out. Also stimulates bones to release Ca2+.
Vitamin D and calcium transport:
Vit D facilitates calcium transport through small intestine epithelial cells.
Formation or sort of… pathway? of vit D:
UV light allows skin to produce vit D from 7-dehydrocholesterol. Also it can be eaten. Two enzymes (one in liver, one in kidney) add one hydroxyl group each to the vit D precursor to make 1,25-dihydroxyvitamin D. This HORMONE is secreted by the kidney and affects the small intestine.
PTH: what it is
Parathyroid hormone. Secreted by parathyroid chief cells. Inhibits osteoblasts to increase Ca2+ concentration in the blood. Enhances vit D production in kidneys. Increases Ca2+ uptake from pretty much everything. Reduces phosphate uptake in kidney.
Osteoblasts, osteoclasts, and PTH receptors:
Osteoblasts have PTH receptors. Osteoclasts do not have PTH receptors (so communication is indirect).
Calcitonin:
Hormone produced in the parafollicular cells of the thyroid gland. Protects bones from Ca2+ loss during pregnancy and lactation (when calcium is mobilized). Reduces blood calcium (inhibit osteoclasts, stimulates osteoblasts, inhibits Ca2+ absorption from intestines and kidneys)
