Lecture 11: Endocrinology Flashcards
Where is ADH made?
Supraoptic nucleus of the hypothalamus
What triggers ADH secretion?
Low blood pressure
Low blood volume
High osmolality
Dehydration
Where is low blood pressure sensed?
Cardiac and aortic baroreceptors
Where is low blood volume sensed?
Atrial stretch receptors
-less stretch can trigger
Where is high osmolality sensed?
Hypothalamic osmoreceptors
What is the secretion of ADH most sensitive to?
Plasma osmolality changes
How does ADH affect blood vessels?
What receptors recognize ADH?
Vasoconstriction –> increases blood pressure and volume
-V1 receptors
How does ADH affect kidneys?
What receptors recognize ADH?
Increases absorption of water –> increases blood pressure and volume
-V2 receptors
How does ADH work?
1) ADH is recognized by V2 receptors on basolateral side principal cells on DCT or collecting duct
2) Aquaporin 2 channels are placed on apical membrane to reabsorb water
3) Water enters blood via aquaporin 3 channels on basolateral side
What happens to a person who is dehydrated?
1) Hypothalamus releases ADH to reabsorb water.
2) Urine becomes more concentrated
What happens to a person who is over-hydrated?
1) ADH is released less
2) Kidneys remove more water
What is diabetes insipidus?
No effect of ADH on renal collecting duct
-frequent urination and thirst
What is the difference between central and nephrogenic diabetes insipidus?
Central: damage to pituitary gland and cannot release ADH
Nephrogenic: ADH released normally but kidneys cannot respond to ADH
How does administration of exogenous vasopressin differentiate central and nephrogenic diabetes insipidus?
Central: Urine osmolarity will increase since ADH is working properly on kidneys
Nephrogenic: Urine osmolarity stays the same because kidneys do not respond to any forms of ADH
Describe SIADH (Syndrome of inappropriate ADH secretion).
Excessive secretion of ADH –> increased water retention
- hyperosmolarity of urine is increased
- ADH still not inhibited
- can be caused by small cell lung carcinoma or issue with posterior pituitary
Where is aldosterone made?
Adrenal cortex
What is aldosterone released in response to?
Low sodium levels or increased potassium levels
Low blood pressure
How does aldosterone work?
1) Aldosterone is recognized by cytoplasmic receptors on principal cells at DCT or collecting duct
2) New protein pumps are secreted on apical side to secrete potassium and increase sodium intake
3) On the basolateral side, Na+/K+ ATPase pumps pushes sodium into the blood
What does angiotensin II promote?
Increased sodium reabsorption
Increased ECF volume
Increased thirst
Increased TPR
Describe primary adrenal insufficiency.
Both cortisol and aldosterone secretion is low
-does not respond properly to ACTH or renin
Describe secondary adrenal insufficiency.
Cortisol production is low but angiotensin-aldosterone axis still exists
ANP and BNP respond to ____ blood pressure.
High blood pressure
Where is ANP found?
Myocytes of atria
How does ANP work?
Increases excretion of NaCl and water by kidneys
-reduces BP
How does BNP work?
Reduces reabsorption of NaCl and water in collecting duct
What does urodilatin do?
Inhibits NaCl and water reabsorption in medullary portion of collecting duct to decrease blood pressure
Natriuretic peptides induce _____ of afferent arterioles and _____ of efferent arterioles of the glomerulus.
Natriuretic peptides induce vasodilation of afferent arterioles and vasoconstriction of efferent arterioles of the glomerulus.
How does the body respond to increased sodium intake?
Decreased sympathetic activity and RAAS
Increased ANP
Decreased oncotic pressure of capillaries
What are causes of hyperkalemia?
Insulin Deficiency β2-adrenergic antagonists α-adrenergic agonists Acidosis Hyperosmolarity Cell lysis Exercise
What are causes of hypokalemia?
Insulin B2-adrenergic agonists α-adrenergic antagonists Alkalosis Hyposmolarity
How does insulin affect potassium levels?
Insulin stimulates potassium uptake
-prevents hyperkalemia
How does 17α-hydroxylase deficiency affect potassium levels?
Decrease potassium levels
How does 21β-hydroxylase deficiency affect potassium levels?
Increase potassium levels
How does 11β-hydroxylase deficiency affect potassium levels?
Decrease potassium levels
