Tubular Processes and Osmoregulation Flashcards
(25 cards)
Where does most reabsorption occur in the nephron?
In the proximal convoluted tubule.
What substances are reabsorbed in the proximal tubule?
Glucose, amino acids, water, Na+, Cl−, bicarbonate.
What is secretion in the nephron?
Movement of substances from blood into the nephron tubule.
What substances are secreted into the nephron tubules?
H+, K+, creatinine, some drugs.
What is the function of the loop of Henle?
To concentrate urine and conserve water.
Which part of the loop of Henle is permeable to water?
The descending limb.
Which part of the loop of Henle actively reabsorbs Na+, K+, and Cl−?
The thick ascending limb.
What is the countercurrent multiplier system?
A system that creates a concentration gradient in the medulla via countercurrent flow.
How does the loop of Henle create a medullary osmotic gradient?
By active salt transport in ascending limb and passive water loss in descending limb.
What is urea recycling and its role?
Urea diffuses from collecting duct into medulla to enhance the osmotic gradient.
What hormone regulates water reabsorption in the collecting duct?
Antidiuretic hormone (ADH or vasopressin).
How does ADH affect the permeability of the collecting duct?
Increases water permeability by inserting aquaporin channels.
What triggers ADH release?
Increased plasma osmolality or decreased blood volume.
What is plasma osmolality?
Concentration of solutes (osmoles) per kg of solvent in plasma.
What detects changes in plasma osmolality?
Osmoreceptors in the hypothalamus.
How does aldosterone affect sodium reabsorption?
Increases sodium reabsorption and potassium secretion.
Where does aldosterone act in the nephron?
Distal tubule and collecting duct.
What is the effect of angiotensin II on the nephron?
Enhances Na+ reabsorption and vasoconstriction.
What is the effect of ANP (atrial natriuretic peptide)?
Inhibits Na+ reabsorption and promotes water excretion.
What is diuresis?
Increased urine output.
What is obligatory water reabsorption?
Water reabsorbed regardless of ADH (e.g., in proximal tubule).
What is facultative water reabsorption?
Water reabsorption regulated by ADH (in collecting duct).
What happens in diabetes insipidus?
Low ADH activity leads to excessive dilute urine.
What is the role of aquaporins?
Water channels in membranes that facilitate water transport.
