KAAP221 Lecture Notes - Lecture 23: Ascending Limb Of Loop Of Henle, Countercurrent Multiplication, Tubular Fluid
11 May 2018
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Lecture 23
• Urinary system part II
• Glomerular filtration rate - GFR
• Amount of filtrate produced by kidneys each minute
• Average - 125 ml/min; 99% of filtrate is reabsorbed
• GFR indicates kidney function - starts to go down as someone progresses through the stages of
kidney disease
• Two interacting levels of control
• Autoregulation - local level within the kidney
• When decreased filtration pressure and decreased filtrate and urine production - manipulate
diameters of afferent and efferent arterioles; dilate afferent - increases blood flow; constrict
efferent - makes it hard for blood to exit
• Central regulation - endocrine and neural systems are involved
• Endocrine response - initiated by kidneys; ANG II
• Juxtaglomerular complex releases renin into the bloodstream, which causes formation of
ANG I, converted to ANG II by angiontensinogen-converting enzyme (ACE) in the
capillaries of the lungs; ANG II constricts peripheral arterioles and further constricts the
efferent arterioles; this increases glomerular blood pressure and systemic BP
• ANG II also triggers increased aldosterone secretion by adrenal glands, which increases
sodium retention
• Neural response - involve sympathetic division of ANS
• Increased ADH production
• Increased stimulation of thirst centers
• Increased sympathetic motor tone
• Reabsorption and secretion
• Reabsorption - occurs mainly in PCT; taking out of tubule and putting them back into the
capillaries
• Reabsorption in PCT includes - >99% of glucose, AA’s, and other organic nutrients; Na+, K+,
HCO3-, Mg+, Phos, sulfate ions; water (60-70% of water in filtrate is reabsorbed), solute
concentration of tubular fluid decreases and water moves into peritubular fluid space and pass
into the capillary
• Secretion - movement of H2O and solutes out of pertiubular fluid into tubular fluid; putting it back
in the trash can; only 15-20% of initial filtrate volume reaches DCT because of reabsorption; Na
ions reabsorbed in exchange for K ions, ion pumps stimulated by aldosterone; H ions secreted in
exchange for Na ions (increase pH of body fluids); carrier proteins also secrete toxins or drugs
• Nephron loop and collecting duct
• Countercurrent multiplication
• Thin descending and thick ascending limbs are located close to each other, so they influence
each other; exchange between these adjacent limbs called countercurrent multiplication
• Countercurrent - fluids moving in opposite directions
• Multiplication - effect increases with fluid movement
• Responsible for creating concentration gradient in renal medulla
• Enables production of highly concentrated urine
• Thick ascending limb
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Document Summary
Lecture 23: urinary system part ii, glomerular filtration rate - gfr, amount of filtrate produced by kidneys each minute. Average - 125 ml/min; 99% of filtrate is reabsorbed. Gfr indicates kidney function - starts to go down as someone progresses through the stages of kidney disease: two interacting levels of control. When decreased filtration pressure and decreased filtrate and urine production - manipulate diameters of afferent and efferent arterioles; dilate afferent - increases blood flow; constrict efferent - makes it hard for blood to exit. Central regulation - endocrine and neural systems are involved. Endocrine response - initiated by kidneys; ang ii. Juxtaglomerular complex releases renin into the bloodstream, which causes formation of. Ang i, converted to ang ii by angiontensinogen-converting enzyme (ace) in the capillaries of the lungs; ang ii constricts peripheral arterioles and further constricts the efferent arterioles; this increases glomerular blood pressure and systemic bp.
