Loop of Henle/Distal Tubule Flashcards
What is the primary function of the thin descending Loop of Henle?
Allow for simple diffusion
What is the thin descending Loop of Henle highly permeable to?
Water
What is the thin descending Loop of Henle moderately permeable to?
Urea and sodium
About how much water is absorbed in the thin descending Loop of Henle?
20%
What part of the Loop of Henle absorbs 25% of sodium, chloride, and potassium (as well as some calcium bicarbonate, and magnesium)?
Thick ascending
In what part of the Loop of Henle is the sodium-potassium ATPase pump highly active?
Thick ascending
Which part of the Loop of Henle is impermeable to water?
Thick ascending
Why is it important that the thick ascending limb of the Loop of Henle is impermeable to water?
Makes kidneys able to dilute or concentrate the urine as needed
What is the first portion of the distal tubule?
Macula densa
What is the function of the macula densa?
Provides feedback control of GFR
The macula densa is a part of what complex?
Juxtaglomerular complex
What ions are absorbed by the diluting segment of the distal tubule?
Sodium, postassium, chloride
The diluting segment of the distal tubule is impermeable to what substances?
Water and urea
What moves sodium chloride from the tubular lumen into the cell in the distal tubule?
Sodium-chloride co-transporter
What moves sodium across the basolateral membrane in the distal tubule?
Sodium-potassium ATPase pump
What two cells compose the late distal tubule and cortical collecting tubule?
Principal cells, intercalated cells
Principal cells function in the reabsorption and secretion of which ions?
Sodium reabsorption
Potassium secretion
Intercalated cells function in the reabsorption and secretion of which ions?
Hydrogen secretion
Bicarbonate and potassium reabsorption
Both the late distal tubule and cortical collecting tubule are impermeable to what substance?
Urea
What happens to most of the urea found in the distal tubule?
Will be excreted in the urine
What hormone controls the reabsorption of sodium and the secretion of potassium in the late distal tubule?
Aldosterone
The permeability of the late distal tubule and cortical collecting tubule to water is dependent on which hormone?
ADH (vasopressin)
What effect do high levels of ADH have on the water permeability of the late distal tubule?
High permeability
What structure plays an important role in the final output of water and solutes in the urine?
Medullary collect duct
Where is urea reabsorbed in the medullary collecting duct?
Medullary interstitium
What is the purpose of hydrogen ions being secreted against a concentration gradient in the medullary collecting duct?
Plays a role in acid-base balance
Pressure natriuresis and pressure diuresis are compensatory mechanisms to regulate what?
Blood pressure (function to increase arterial BP)
What is natriuresis?
Increased sodium ion excretion in urine to increase BP
What is diuresis?
Increased water excretion to regulate BP
Why do we only seen small changes in excretion with pressure natriuresis and pressure diuresis?
Autoregulatory mechanisms
Increase in what kind of pressure causes backleak of sodium into the tubular lumen and increased urine output during pressure natriuresis and diuresis?
Peritubular hydrostatic pressure
What effect does a reduction in angiotensin II formation have on tubular sodium reabsorption when arterial BP increases?
Decreased tubular sodium reabsorption
The rate of which hormone is a major determining fact for urine concentration?
ADH
What happens to the osmolarity of filtrate at the beginning of the proximal tubule to the end of the proximal tubule?
Stays isotonic
Where is water reabsorbed by osmosis in the loop of Henle?
Descending segment
Does tubular fluid becomes more or less concentrated as it travels into the medulla?
More
Is renal medulla interstitial fluid more hyper- or hypotonic?
Hypertonic
Which segments of the Loop of Henle are NOT permeable to water?
Thin and thick ascending
How are solutes transported out of the thick ascending segment of the Loop of Henle?
Active transport
Does tubular fluid become more dilute or more concentrated as it travels up the ascending segment of the loop of Henle?
More dilute
As tubular fluid enters the Loop of Henle, is it isotonic, hypertonic, or hypotonic?
Isotonic
As tubular fluid leaves the Loop of Henle, is it isotonic, hypertonic, or hypotonic?
Hypotonic
What measurement is used to assess the concentration of urine?
Urine Specific Gravity
Does a high specific gravity measurement mean there is high or low concentration of urine?
High
What are the two basic requirements for forming a concentrated urine?
High level of ADH
High osmolarity in medulla tissue
How do we create a hyperosmotic renal medullary interstitial fluid?
Countercurrent mechanism
What factors contribute to the buildup of solute concentration into the renal medulla?
Active transport of sodium from thick ascending limb to medullary interstitium
Active transport of ions out of collecting ducts into medullary interstitium
Diffusion of urea from inner medullary collecting ducts into medullary interstitium
Low diffusion of water compared to solute reabsorption
What is the term for the repetitive reabsorption of the sodium chloride by the thick ascending loop of Henle and continued inflow of new sodium from the proximal tubule into the loop of Henle?
Countercurrent multiplier
When do the collecting ducts become permeable to fluid?
When high levels of ADH are present
Where do we see a high concentration of urea?
Inner medullary collecting ducts
What effect do the vasa recta have on the solute concentration in the renal medulla?
Preserve the high concentration levels
Where is the thirst center located?
Anterolateral in preoptic nucleus
What area promotes the release of ADH to stimulate thirst?
Anteroventral wall of third ventricle
What levels of plasma osmolarity increases thirst?
Increased
What levels of blood volume increases thirst?
Decreased
What levels of blood pressure increases thirst?
Decreased
What levels of angiotensin II increase thirst?
Increased
What effect does gastric distention have on thirst?
Decreased
What determines extracellular fluid volume?
Intake and output of fluid and sodium (habitual)
What happens to the kidneys if they are unable to maintain the proper balance of extracellular fluid?
1 Adjustment of BP
2 Adjustment of circulating hormones
3 Adjustment in sympathetic nervous system changes
What is the cost of the kidneys making systemic adjustments to compensate for imbalance of extracellular fluid?
Damage possible and energy lost
What is the benefit to increased blood pressure as a response to kidney damage?
Helps maintain normal sodium excretion
What is the cost to increased blood pressure as a response to kidney damage?
Long term high blood pressure damage to blood vessels, heart, and organs
What is the effect on increased blood pressure on sodium excretion?
Increases it
Extensive decrease in blood volume (hemorrhage) will activate what kind of nerve activity?
Sympathetic
Angiotensin II controls the excretion of which ions?
Sodium
What levels of sodium lead to decreased production of renin?
High
What is the relationship between angiotensin II and “salt-sensitive people”?
They are unable to stop the angiotensin II formation in response to increased sodium levels
What effect does increased aldosterone have on potassium excretion?
Increased
What effect does increased aldosterone have on sodium and water reabsorption in the cortical collecting tubules?
Increased
What effect do alcohol, clonidine, and haloperidol have on ADH secretion?
Inhibition
What effect do nausea, hypoxia, morphine, nicotine, and cyclophosphamide have on ADH secretion?
Increase
