lesson 16 transcript + study guide Flashcards
osmolarity
The concentration of solute particles in a solution (measured in osmoles/L).
tonicity
The ability of a surrounding solution to change the volume of a cell via osmosis.
What is homeostasis in terms of fluid balance?
The regulation of water and solute concentrations to maintain a stable internal environment.
What are the three main processes of the excretory system?
Filtration, reabsorption, and secretion.
What is the main organ of osmoregulation in vertebrates?
kidney
What nitrogenous waste do mammals primarily excrete?
Urea (less toxic, water-soluble, excreted in urine).
What waste form is used by birds, reptiles, and insects? Why?
Uric acid—uses less water, helps conserve water.
Where does filtration begin in the nephron?
In the glomerulus inside the Bowman’s capsule.
What causes fluid to leave the blood at the glomerulus?
Blood pressure forces water and small solutes through capillary pores.
What substances are filtered at the glomerulus?
Water, ions, glucose, urea, and small molecules.
What stays in the blood during glomerular filtration?
Blood cells and large proteins.
What is the correct pathway through the nephron?
Bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting duct
Where does urine go after the collecting duct?
Renal pelvis
Ureter
Bladder
Urethra
Where is most water reabsorbed in the nephron?
Proximal tubule, descending loop of Henle, and collecting duct.
How is water reabsorbed?
By osmosis due to salt gradients created by active sodium transport.
Where are glucose and amino acids reabsorbed?
In the proximal convoluted tubule by active transport.
Where does secretion of unwanted substances occur?
Primarily in the distal convoluted tubule.
What part of the nephron uses countercurrent flow?
The loop of Henle.
What is the function of the descending limb of the loop of Henle?
Reabsorbs water; impermeable to salt.
What is the function of the ascending limb?
Reabsorbs salt (NaCl); impermeable to water.
What is the result of this countercurrent system?
Creates an osmotic gradient that allows the collecting duct to concentrate urine.
What does ADH stand for
Antidiuretic Hormone
When is ADH released
When blood osmolarity is high (dehydration)
What does ADH do?
Increases water reabsorption in the distal tubule and collecting duct by inserting aquaporins.
What is the effect of ADH on urine?
Produces less, more concentrated urine.
How does ADH affect blood volume and pressure?
Increases both by reabsorbing more water into the blood.
