Renal 2 Flashcards
What is osmoregulation, and why is it important?
Osmoregulation is the balance of water and electrolytes in body fluids, ensuring a stable osmolarity of ~300 mOsm/kg. This prevents cell swelling or shrinking, which could disrupt cellular function.
How do osmoreceptors regulate ADH release?
Osmoreceptors in the anterior hypothalamus detect changes in ECF osmolality. When osmolality increases, ADH is released from the posterior pituitary, increasing water reabsorption in the collecting duct.
How does ADH affect the kidney?
ADH binds to V2 receptors in collecting duct principal cells, triggering aquaporin-2 insertion in the apical membrane. This increases water permeability, allowing water to move into the hyperosmotic medulla and concentrating urine.
What is the role of aldosterone in sodium regulation?
Aldosterone increases Na⁺ reabsorption and K⁺ secretion in the collecting duct by upregulating Na⁺/K⁺-ATPase activity. This helps maintain ECF volume and blood pressure.
How does the loop of Henle contribute to urine concentration?
- Descending limb: Permeable to water, impermeable to NaCl, leading to water reabsorption.
- Thin ascending limb: Impermeable to water, permeable to NaCl, leading to passive Na⁺ reabsorption.
- Thick ascending limb: Impermeable to water, actively transports Na⁺, K⁺, and Cl⁻ (via NKCC2), diluting the filtrate.
Plasma osmolality is ~300 mOsm/kg; deviations trigger
ADH release.
ADH increases water reabsorption by inserting a
quaporin-2 channels.
Renin release is triggered by
Low blood pressure, low Na⁺, or sympathetic activation.
Aldosterone promotes Na⁺ retention and K⁺ excretion, increasing
blood volume.
The countercurrent multiplier in the loop of Henle establishes
an osmotic gradient.
The countercurrent exchanger in the vasa recta prevents
washout of the gradient.
Urea recycling contributes to
medullary hyperosmolarity, aiding water reabsorption.
ADH increases Na⁺ reabsorption in the distal tubule.
False (ADH increases water reabsorption, not Na⁺.)
The thick ascending limb of the loop of Henle actively transports Na⁺ but is impermeable to water.
True
Aldosterone acts directly on the hypothalamus to stimulate thirst.
False (Angiotensin II, not aldosterone, stimulates thirst.)
Urea contributes to medullary osmolarity by recycling between the collecting duct and the loop of Henle.
True
The countercurrent exchanger in the vasa recta helps maintain the renal medullary gradient.
True
______ is the primary hormone regulating water balance in the kidney.
Antidiuretic hormone (ADH)
Aldosterone increases Na⁺ reabsorption and ______ secretion.
K⁺
The countercurrent multiplier is established by the ______ and helps create a medullary osmotic gradient.
Loop of Henle
The V2 receptor for ADH is located on the ______ membrane of principal cells.
Basolateral
Renin release is stimulated by low blood pressure, low NaCl delivery, and ______ activation.
Sympathetic nervous system
Which of the following triggers ADH release?
A) Increased plasma osmolality
B) Increased blood volume
C) High Na⁺ levels in urine
D) Low K⁺ levels in plasma
A) Increased plasma osmolality
What is the effect of aldosterone on kidney function?
A) Increases Na⁺ excretion and reduces blood pressure
B) Increases Na⁺ reabsorption and K⁺ secretion
C) Inhibits renin release and promotes diuresis
D) Increases urea excretion and prevents water reabsorption
B) Increases Na⁺ reabsorption and K⁺ secretion
