Questions and Answers
Which nephron type is characterized by long nephron loops and a higher glomerular filtration rate?
What is the primary difference in structure between cortical and juxtamedullary nephrons?
Cortical nephrons have short nephron loops, while juxtamedullary nephrons have long nephron loops that maintain a salt gradient.
What is the difference in osmolarity between blood plasma and renal medulla?
The osmolarity of the renal medulla is higher than that of blood plasma.
How is the osmotic gradient of the renal medulla maintained?
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What is the function of the vasa recta?
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What is renal autoregulation?
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What is the effect of sympathetic control on GFR?
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How does angiotensin II influence glomerular filtration rate?
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What is the main function of peritubular capillaries?
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What is reabsorbed by the proximal convoluted tubule?
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How do permeability characteristics of the loop of Henle differ?
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Where does urea recycling occur and what is its function?
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Where are the receptors for aldosterone and ADH located?
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What are the effects of ADH, ANP, and aldosterone on the kidney?
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Describe the renin-angiotensin-aldosterone pathway.
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What are the typical constituents of urine?
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How do transport maxima and GFR affect reabsorption?
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Study Notes
Nephron Types
- Cortical nephrons (85%): Short nephron loops with glomeruli in the outer renal cortex; responsible for excretory and regulatory kidney functions.
- Juxtamedullary nephrons (15%): Long loops of Henle that penetrate deeply into the medulla; crucial for maintaining osmotic gradient and concentrating urine.
Osmolarity
- Blood plasma osmolarity is crucial for physiological functions, while renal medulla osmolarity is involved in urine concentration and water balance.
Loop of Henle Function
- Establishes osmotic gradient in the renal medulla, preventing excessive production of dilute urine.
- Ascent and descent differ in permeability: descending limb is permeable to water; ascending limb is impermeable to water but allows solute diffusion.
Vasa Recta Structure and Function
- Vasa recta provides blood supply to the medulla with high permeability to solutes and water.
- Responsible for nutrient delivery and efficient removal of excess solutes and water from the interstitium.
Renal Autoregulation of GFR
- Nephrons can self-regulate blood flow and GFR, maintaining stable filtration rates despite fluctuations in arterial blood pressure.
ANS and GFR Control
- Sympathetic nervous system stimulation constricts afferent arterioles during stress, reducing GFR and redirecting blood to vital organs.
Renin-Angiotensin System
- Drop in blood pressure activates baroreceptors, stimulating renin release, which triggers a cascade increasing blood volume and pressure via angiotensin II.
Peritubular Capillaries
- High colloid osmotic pressure (COP) and low blood hydrostatic pressure (BHP) favor reabsorption of water and solutes back into circulation.
Nephron Components and Functions
- Different nephron segments (proximal convoluted tubule, loop of Henle, distal convoluted tubule) are specialized for filtration, absorption, and secretion.
Proximal Convoluted Tubule Functions
- Reabsorbs 65% of glomerular filtrate, including NaCl, K, water, glucose, and bicarbonate.
- Secretes waste products such as urea and ammonium ions.
Urea Recycling
- Occurs in the collecting duct and medulla; urea contributes to the osmolarity gradient, aiding in urine concentration.
Aldosterone and ADH Effects
- Aldosterone promotes sodium and water reabsorption in the distal tubule and collecting duct.
- ADH increases water reabsorption in the collecting duct, concentrating urine and reducing volume.
- Atrial Natriuretic Peptide (ANP) has opposite effects, promoting sodium and water excretion.
Renin-Angiotensin-Aldosterone Pathway
- Involves complex interactions starting from renin release to increasing blood pressure and fluid balance through angiotensin II and aldosterone.
Urine Composition
- Normal urine composition: 95% water, 5% solutes (urea, NaCl, KCl, creatinine).
- pH typically ranges from 4.5 to 8.2, usually around 6.0; elevated solutes like proteins should not be present.
Transport Maxima and GFR
- Transport maximum influences reabsorption capacity; if limits are exceeded, certain substances may remain in filtrate despite normal GFR levels.
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Description
Explore the differences between cortical and juxtamedullary nephrons in this quiz. Learn how each type contributes to kidney function, especially in water conservation and osmotic gradient maintenance. Test your understanding of nephron structures and their roles in urine formation.