6/10- parathyroid + pancreas physio

which 3 organ systems are involved in calcium homeostasis

1. GI tract

2. kidneys

3. bone

phosphate is regulated by which 3 organ systems

1. GI tract

2. kidneys

3. bone

3 types of bone cells

1. osteoblasts

2. osteocytes

3. osteoclasts

what’s osteoclastogenesis

creation of osteoclast precursors via:

1. Vit D proliferation

2. M-CSF proliferation

3. RANKL proliferation

M-CSF + RANKL are from osteoblasts stimulated by parathyroid hormone (PTH)

what 3 hormones regulate calcium + phosphorus levels

1. parathyroid hormone (PTH): increases blood Ca²⁺

2. 1,25-(OH)₂ Vit D3: increases blood Ca²⁺

3. calcitonin: decreases blood Ca²⁺

parathyroid hormone (PTH) is produced by what

chief cells in the parathyroid glands

how does PTH increase blood calcium

1. increasing kidney reabsorption of calcium

2. increasing reabsorption of bone

3. increasing conversion of inactive vit D3 → active form 1,25-(OH)₂ Vit D3 (calcitriole), increasing intestinal calcium uptake + promotes actions of PTH on bone

which kidney cells are effected by PTH

1. increases calcium reabsorption in thick ascending loop of Henle + DCT cells

2. decreases reabsorption of phosphate in PCT + DCT

how does PTH increase bone reabsorption

1. PTH binds to osteoblasts to induce cytokine secretion: M-CSF, IL-6, RANKL

2. inhibits collagen synthesis by osteoblasts + promotes production of bone matrix proteases

which organs involve formation of Vit D3 active form

1. skin

2. liver

3. kidneys

vit D3’s effect on the GI tract

1. increases synthesis of Ca²⁺ pumps, channels and calbindin to increase Ca²⁺ absorption in duodenum

2. increases phosphate absorption in duodenum

vit D3’s effect on the kidneys

increases Ca²⁺ and Pi reabsorption

vit D3’s effect on bone

mobilizes Ca²⁺ from bone + PTH

vit D3 deficiency leads to

loss of bone minerals → rickets in children or osteomalacia in adults

calcitonin is produced by which cells

parafollicular cells in the thyroid gland + stored in secretory granules

calcitonin secretion is triggered by

increasing plasma Ca²⁺

2 effects of calcitonin

1. bone: binds to osteoclasts + inhibits bone reabsorption

2. kidneys: increases calcium + phosphate elimination

4 hormones secreted by the pancreas

1. insulin

2. glucagon

3. somatostatin

4. pancreatic polypeptide

which cells of the pancreas release the hormones

within the Islets of Langerhans:

1. alpha cells: glucagon

2. delta cells: somatostatin

3. F cells: pancreatic peptides

when is glucagon secreted

1. during fasting between meals aka hypoglycemia

2. low insulin

3. amino acids

4. sympathetic stimulation

effect of glucagon

1. promotes glycogenolysis, glucose production, lipolysis, + ketogenesis in liver

2. w/ cortisol: promotes gluconeogeneis + ureagenesis in liver

glucagon is inhibited by

somatostatin + fatty acids

what happens when blood glucose level is too high

negative feedback loop: signals alpha cells of pancreatic islets to stop releasing glucagon

effect of somatostatin

acts on target cells by binding to G-protein-coupled receptors to regulate parts of the endocrine system

which hormones of which glands are effected by somatostatin

1. pancreas: insulin + glucagon

2. hypothalamus: GH, TSH

3. anterior pituitary: corticotropin

4. GI tract: gastrin

5. thyroid: T3, T4, calcitonin

6. adrenal: aldosterone

T/F: somatostatin’s half-life is very short so it’s mainly used to fine-tune endocrine activity

true

role of pancreatic polypeptide

modulate digestion of food by inhibiting gastric emptying + biliary secretion