Endocrine Pathways Flashcards
1
Q
Renin-angiotensin pathway
A
- Decrease in BP and/or Na+ conc stimulate secretion of renin enzyme from kidneys
- Renin enzyme acts on angiotensinogen (inactive) from liver to make angiotensin 1 (inactive)
- Angiotensin 1 is converted to angiotensin 2 (active) in the lung epithelium by ACE (angiotensin converting enzyme)
- Angiotensin 2 is a vasoconstrictor (which increases BP), and it also stimulates adrenal cortex cells of the Z. Glomerulosa to secrete aldosterone
- Aldosterone acts on the kidney to conserve Na+ and water, which increases BP through increase in blood volume
- Aldosterone also promotes secretion of K+ and H+ through urine
- Blood pressure returns to normal, renin secretion inhibited
2
Q
Blood Ca2+/Vit D pathway
A
- Ingest cholesterol and cholecalciferol from foods
- Sunlight converts cholesterol into cholecalciferol
- Liver adds -OH to make calcidiol
- Kidney adds -OH to make calcitriol (active Vit D), and is released into blood
- Hypocalcemia stimulates PTH release
- PTH and calcitriol work synergistically at kidney decreasing Ca2+ loss in urine
- Calcitriol increases absorption of Ca2+ in small intestine
- PTH and calcitriol act synergistically increasing osteoclasts activity, resorption of bone matrix, resulting in Ca2+ release from bone
- Increase in blood Ca2+ inhibits PTH
3
Q
Growth Hormone pathway
A
- Hypothalamus stimulated by age, time of day, nutrient levels in blood, stress, exercise
- Hypothalamus releases GHRH to ant pit
- Ant pit releases GH
- GH acts on liver to make IGF1
- Both GH and IGF1 act on effector cells/organs
- Liver increases glycogenolysis and gluconeogenesis, decreases glycogenesis
- Adipose tissue increases lipolysis and decreases lip-genesis
- Bone, cartilage, muscle, and all other cells use glucose and amino acids to grow, differentiate, divide
- Net effect is increased protein synthesis, cell division, cell differentiation
- Increase GH in blood neg feedback on ant pit
- Increase GH and IGF1 neg feedback on hypothalamus
4
Q
Thyroid hormone pathway
A
- Hypothalamus stimulated by decrease in TH (T3/T4 ), cold weather, pregnancy, high altitude, hypoglycemia
- Hypothalamus releases TRH (thyrotropin releasing hormone)
- Ant pit releases TSH
- Thyroid releases TH (T3/T4)
- TH (T3/T4) bound by carrier protein in blood
- T4 most abundant in blood, converted to more potent T3 at target cells
- Adipose tissue increases lipolysis and decreases lipogenesis
- Liver increases glycogenolysis and gluconeogenesis, decreases glycogenesis
- All cells, esp neurons, take up glucose and amino acids, increased metabolic rate
- Lung and heart increase rates to meet increased demand for O2 for aerobic metabolism
- Net effect: increased metabolic rate occurs, which is supported by increased release of stored nutrients, and increased deliver of O2
- TH levels in blood increase, inhibiting release of TRH and TSH
5
Q
Cortisol pathway
A
- Hypothalamus stimulated by time of day and stress
- Hypothalamus releases CRH (corticotropin releasing hormone)
- Ant pit releases ACTH (adrenocorticotropic hormone)
- ACTH stimulates adrenal cortex to release glucocorticoids (e.g. cortisol) from the Z. Fasciculata into the blood
- cortisol bound by carrier proteins in blood
- Stimulates liver to increase glycogenolysis and gluconeogenesis, and decrease glycogenesis
- Adipose cells increase lipolysis and decrease lipogenesis
- All cells have stimulation of protein catabolism (breakdown), and decreased glucose uptake
- High cortisol increases retention of Na+ and H2O, decrease inflammation, suppresses immune system, and inhibits connective tissue repair
- Net effect: increase of all nutrients in blood (think stress for fight/flight)
- Increase levels of cortisol inhibits CRH and ACTH release
6
Q
Insulin pathway
A
- Pancreas stimulated by increase in BGL (blood glucose level)
- Pancreatic Beta cells release insulin into blood, travels to target cells (effectors)
- Liver uses glucose for glycogenesis, decreased glycogenolysis and gluconeogenesis
- Adipose cells take in fatty acids to increase lipogenesis and decrease lipolysis
- All cells (esp muscle) take in amino acids, which stimulates protein anabolism (growth)
- Most cells take in glucose
- Net effect: decreased BGL, fatty acids, and amino acids in blood
- Insulin release inhibited as BGL drops
7
Q
Glucagon pathway
A
- Pancreas stimulated by decrease in BGL
- Pancreatic alpha cells release glucagon
- Glucagon travels in blood to effector organs/cells for stimulation
- Adipose cells increase lipolysis and decrease lipogenesis
- Liver increases glycogenolysis and gluconeogenesis, decreases glycogenesis
- Net effect: increase in BGL and fatty acid levels in blood to be used by cells for energy
- Rise in BGL inhibits glucagon release
