Exam 5: Water Balance Flashcards
What is the late distal tubule and collecting duct the site of action for?
ADH
What does ADH bind to?
Receptors on basolateral surface
What happens when ADH binds to receptors on the basolateral surface?
Stimulates insertion of aquaporins in the apical membrane
Water moves into renal medullary interstitium
What are aquaporins?
Channels for free water transport
What are the net effects of ADH?
Free water resorption
Concentrated urine
What stimulates the release of ADH?
Increased peripheral osmolality
Hypovolemia (if severe)
Other hypothalamic stimuli (pain, fear, anxiety, nausea)
What is hyperosmolality caused by?
Salt overload
Dehydration
What is the primary stimulus of ADH?
Osmolarity
What is the primary stimulus of aldosterone?
Hypovolemia
What does aldosterone result in?
Sodium and water resorption
Expands blood volume
Where is the thirst center?
Hypothalamus
What osmoreceptors is the thirst center close to?
Those for ADH secretion
What are the stimuli for the thirst center?
Increased osmolality
Decreased blood pressure/volume
Increased AT II
Dry mouth
What does the thirst center work with?
ADH
They compensate for each other
