renal 2 Flashcards
What are the three main processes of urine formation in the nephron?
Glomerular filtration, tubular reabsorption, and tubular secretion.
What role do podocytes play in glomerular filtration?
They form filtration slits with foot processes, allowing selective filtration based on size and charge.
What is the effect of a 25% drop in systemic blood pressure on filtration?
It reduces glomerular hydrostatic pressure, decreasing net filtration pressure and GFR.
List the three mechanisms that regulate glomerular filtration rate (GFR).
Autoregulation, hormonal regulation, and autonomic nervous system regulation.
How does autoregulation maintain GFR during blood pressure fluctuations?
By adjusting the diameters of afferent and efferent arterioles through myogenic responses.
What does atrial natriuretic peptide (ANP) do to GFR?
It increases GFR by dilating afferent arterioles and relaxing mesangial cells, increasing filtration surface area.
What is the role of the proximal convoluted tubule (PCT)?
Reabsorbs 60-70% of filtrate, including most glucose, amino acids, sodium, chloride, and water.
Which transport mechanisms are involved in PCT reabsorption?
Sodium diffusion, Na+/K+ ATPase, cotransporters (e.g. glucose), chloride diffusion, and osmosis for water.
What does the descending limb of the loop of Henle do?
It reabsorbs water by osmosis, making urine more concentrated.
What does the ascending limb of the loop of Henle do?
Actively reabsorbs sodium and passively reabsorbs chloride, making urine more dilute.
What is countercurrent multiplication in the loop of Henle?
A mechanism that establishes an osmotic gradient in the medulla, enabling water reabsorption from the collecting duct.
Why is the loop of Henle essential for concentrating urine?
It creates a medullary osmotic gradient via differential permeability to water and ions in its limbs.
What regulates water reabsorption in the distal convoluted tubule (DCT) and collecting duct?
Antidiuretic hormone (ADH) and aldosterone.
What does ADH do at the collecting duct?
Inserts aquaporin-2 channels to increase water permeability and reabsorption.
What is the mechanism by which ADH increases water reabsorption?
Via protein kinase A, ADH induces aquaporin-2 channel insertion into the luminal membrane.
What is aldosterone’s role in renal physiology?
Promotes sodium reabsorption and potassium secretion in the distal nephron.
How do diuretics affect kidney function?
They increase water excretion by reducing reabsorption, often by inhibiting sodium transport.
What are the two major hormone types that affect kidneys?
Steroid hormones (e.g. aldosterone) and peptide hormones (e.g. ADH).
What are the major osmoregulatory challenges in freshwater environments?
Excess water influx and salt loss.
How do freshwater fish deal with osmoregulatory challenges?
They excrete dilute urine and actively reabsorb salts via gills.
What are the osmoregulatory challenges in saltwater environments?
Water loss and salt gain.
How do saltwater fish maintain osmotic balance?
By drinking seawater, excreting concentrated urine, and actively excreting salts via gills.
What are the osmoregulatory challenges of terrestrial animals?
Water loss through evaporation and risk of salt imbalance.
How do land animals conserve water?
By producing concentrated urine and using salt glands or dietary salt management.
