AP 24 Nov Lecture 33 Flashcards
What are water conservation states?
Characteristics of a system aimed at conserving water within the nephron
What is the osmolarity of tubular fluid in the proximal tubule?
About 300 mOsm/L
Why is the osmolarity in the proximal tubule the same as plasma osmolarity?
Because it reabsorbs electrolytes and glucose, allowing water to follow
What happens to tubular fluid as it moves deeper into the kidney?
It becomes more concentrated due to water reabsorption
What is the maximum osmolarity that can be achieved in the kidney?
1200 mOsm/L
What is the permeability of the thin ascending limb of the loop of Henle?
Not very permeable to water
What is reabsorbed in the thick ascending limb of the loop of Henle?
Lots of solutes, including 25% of all filtered solutes
What is the osmolarity of tubular fluid in the thick ascending limb?
Diluted to about 100 mOsm/L
What role do principal and intercalated cells play in water conservation?
They can be permeable to water in the presence of ADH
What happens to osmolarity in the collecting ducts if water channels are present?
Osmolarity increases, reflecting the concentration of renal interstitial fluid
What is the osmolarity of urine during water conservation mode?
Can reach up to 1200 mOsm/L
What occurs during a water excess state?
Interstitial osmolarity decreases to about 600 mOsm/L
What is the effect of ADH on water reabsorption?
Increases water reabsorption in the collecting duct
What happens to osmolarity in the proximal tubule during water excess?
Remains the same as what was filtered
What occurs in the diluting segment of the nephron?
Fluid is diluted regardless of ADH presence
What happens to creatinine concentration in the nephron?
Increases due to water reabsorption without reabsorption of creatinine
What is the role of the NKCC/NCCK pump?
Reabsorbs sodium, potassium, and chloride ions
What is the characteristic of PAH in the nephron?
Easily filtered and heavily secreted
What is the effect of diuretic therapy on fluid excretion?
Causes an increase in fluid excretion from the body
What happens to sodium and water excretion with diuretic use?
Both sodium and water excretion increase
Fill in the blank: The osmolarity in the thick ascending limb dilutes tubular fluid to _______.
100 mOsm/L
True or False: The second half of the loop of Henle is permeable to water.
False
What is the relationship between salt intake and water intake?
High salt intake usually correlates with high water intake
What is diuresis?
Loss of fluid and electrolytes
Diuresis refers to the increased production of urine, which results in the loss of fluid and electrolytes from the body.
What components make up extracellular fluid (ECF)?
Plasma portion (1/5) and interstitial portion (4/5)
The extracellular fluid is divided into two components: the plasma portion, which constitutes one-fifth of the ECF, and the interstitial portion, which makes up the remaining four-fifths.
What happens to urine output when a person is initially exposed to diuretic drugs?
Urine output goes way up
When a patient first takes diuretic medication, there is typically a significant increase in urine output as the body begins to excrete excess fluid.
True or False: The primary effect of diuretics is to maintain fluid balance over the long term.
True
Diuretics primarily help maintain fluid balance by promoting the excretion of excess fluid, which can help manage conditions like hypertension.
What is the relationship between vascular resistance and blood pressure?
Increased vascular resistance leads to increased blood pressure
Blood pressure is determined by the resistance in the vascular system; higher resistance results in higher blood pressure.
What role does Angiotensin II play in sodium and fluid balance?
Regulates sodium reabsorption and blood pressure
Angiotensin II is crucial in managing sodium reabsorption in the kidneys, influencing blood pressure by affecting fluid balance.
Fill in the blank: If angiotensin II levels are high, we would expect arterial blood pressure to ______ if salt intake is increased.
Rise
High levels of angiotensin II lead to increased sodium retention, which can raise blood pressure when salt intake is increased.
What happens if there is a blockade of the angiotensin system?
Difficult to maintain normal blood pressure
Blocking the angiotensin system can lead to low blood pressure due to inadequate sodium reabsorption and fluid retention.
How does a high sodium diet affect angiotensin II levels?
It suppresses angiotensin II levels
A diet high in sodium can lead the body to decrease angiotensin II levels to help manage excess salt intake.
What is the effect of renal artery stenosis on glomerular filtration rate (GFR)?
Decreases GFR
Renal artery stenosis leads to lower blood pressure in the affected kidney, resulting in decreased glomerular filtration rate.
True or False: Both kidneys are affected by angiotensin II when one kidney has stenosis.
True
Angiotensin II will act on both kidneys, leading to conservation of water and increased blood pressure in response to perceived low blood pressure.
What dietary habit can lead to a low angiotensin II level?
Consuming a diet high in processed and salty foods
A diet consisting mainly of salty processed foods can lead to low levels of angiotensin II, as the body adapts to excess sodium intake.
What is the effect of high renin output from the kidney?
Leads to high blood pressure
High renin output can cause significant hypertension, although the presence of a healthy kidney can mitigate it.
How does the kidney on the right respond to high renin output from the left kidney?
It cannot reduce its renin output enough to compensate
This results in elevated blood pressure, especially if renal artery stenosis is present.
What happens to glomerular capillary pressure over time due to high blood pressure?
It can lead to damage of the capillary beds
Prolonged high pressure can result in permanent damage, affecting kidney function.
What is a potential treatment for renal artery stenosis?
Stenting the renal artery
This procedure aims to relieve the stenosis and improve blood flow.
What class of medication is recommended to limit crosstalk between kidneys in hypertension?
ACE inhibitors
ACE inhibitors reduce the effects of angiotensin II, which is involved in kidney communication affecting blood pressure.
What is diuresis?
Increased excretion of fluid and electrolytes
This process is often a response to high sodium intake and helps regulate blood pressure.
What occurs when there is a high salt diet?
Increased sodium concentration in blood and filtrate
This leads to renin release repression, helping to excrete excess salt.
True or False: High blood pressure leads to decreased filtration rates at the glomerular capillaries.
False
High blood pressure typically increases filtration rates initially.
What is the relationship between sodium intake and renin release?
Excess sodium represses renin release
This helps the body to eliminate excess sodium and maintain balance.
What is essential hypertension?
Chronic high blood pressure not significantly affected by salt intake
Patients with essential hypertension often do not see major changes in blood pressure with varying sodium and fluid intake.
What characterizes salt-sensitive hypertension?
Blood pressure is directly dependent on salt intake
Conditions like renal vascular hypertension exhibit this sensitivity.
What is an unexpected finding in salt-sensitive hypertension among African Americans?
It is often a low renin form of hypertension
This contrasts with the expected high renin activity in cases of salt sensitivity.
Fill in the blank: Excess sodium delivered to the macula densa leads to _______ release.
renin
What happens to blood volume with increased sodium intake?
It increases
Higher blood volume can contribute to increased blood pressure.
What role do taste buds play in sodium perception?
They become more excitable with increased sodium concentration
This enhances the ability to taste flavors.
What is the typical response of the kidney to low blood pressure?
Increases renin release
This mechanism helps conserve blood volume and maintain pressure.
What role do genes play in blood pressure?
Genes play a huge role in determining blood pressure levels
While diet can influence blood pressure, genetics is usually the primary factor.
What is the function of osmotic diuretics like mannitol?
Osmotic diuretics like mannitol get filtered but not heavily reabsorbed, leading to decreased water reabsorption
Mannitol and excess blood glucose act as osmotic diuretics by remaining in the tubule.
How do angiotensin receptor blockers (ARBs) affect sodium reabsorption?
ARBs affect sodium reabsorption by reducing the interaction with angiotensin II at AT-1 receptors
This leads to decreased sodium reabsorption in the proximal tubules.
What is the normal blood concentration of creatinine?
Normal blood concentration of creatinine is about 1 mg/dL
This value is used as a reference in assessing kidney function.
What is creatinine clearance and how is it estimated?
Creatinine clearance is estimated by measuring blood creatinine levels, typically used as a marker for clearance
Inulin can provide a more accurate estimate of GFR.
What is the equation for creatinine excretion?
Creatinine excretion = amount filtered + amount secreted
Neither amount is reabsorbed; thus, excretion equals the sum of filtration and secretion.
What happens to creatinine clearance after unilateral nephrectomy?
Creatinine clearance is likely cut in half after unilateral nephrectomy
This is due to the loss of half the nephrons.
What occurs to blood creatinine concentration after nephron loss?
Blood creatinine concentration rises as nephron loss decreases filtration
This occurs until plasma concentration increases enough to restore balance between production and excretion.
What must happen for creatinine production and excretion to return to balance after nephron loss?
Creatinine concentration in the blood must rise to match the reduced excretion rate
This adjustment allows for the same amount of creatinine to be filtered despite decreased fluid volume.
True or False: ACE inhibitors are less effective in individuals with low renin levels.
True
ACE inhibitors may still be useful in these cases despite lower efficacy.
Fill in the blank: The filtration rate of creatinine is typically _____ mg/min.
1.25 mg/min
This is based on normal filtration rates in healthy individuals.
What is the expected plasma creatinine concentration after losing half the nephrons?
Plasma creatinine concentration is expected to double
This doubling occurs as the body adjusts to the decreased ability to excrete creatinine.
What is the primary means by which creatinine is removed from the body?
Filtration is the primary means of creatinine removal
There is minimal reabsorption of creatinine in the kidney.
What happens to nephrons as blood pressure increases?
Nephrons are likely to disappear faster
Higher blood pressure subjects nephrons to more stress, leading to their loss over time.
What is the relationship between nephron loss and creatinine concentration in the blood?
As nephrons are lost, creatinine concentration rises due to an imbalance between excretion and production
Reduced nephron count leads to decreased filtration and increased creatinine levels.
What is physiological hypertrophy in the context of nephrectomy?
The remaining kidney increases its workload and size after the removal of one kidney
This adaptation helps maintain a relatively normal GFR.
How much can the remaining kidney increase its GFR after unilateral nephrectomy?
By about 50%
This increase helps compensate for the loss of the other kidney.
True or False: The systemic blood pressure changes significantly after a unilateral nephrectomy.
False
The pressure within the kidney remains relatively stable despite nephrectomy.
What happens to nephron workload when 75% of nephrons are lost?
The remaining nephrons experience increased stress and workload
This can lead to a shorter life expectancy for the remaining nephrons.
What are the consequences of high workload on remaining nephrons?
It can lead to progressive nephron loss and renal failure
Increased workload accelerates damage and dysfunction over time.
What dietary restrictions are recommended for individuals with reduced nephron function?
Sodium and potassium restriction, and moderation of protein intake
These restrictions help reduce the workload on remaining nephrons.
What role do kidneys play in acid-base balance?
They are responsible for excreting acids and can regulate bicarbonate levels
Impaired kidney function can lead to metabolic acidosis.
What is the normal blood osmolarity level in mOsm/L?
About 300 mOsm/L
This is the standard osmolarity before any corrections are made.
What effect does isotonic saline have on extracellular fluid?
It expands the extracellular fluid compartment without causing water shifts
Isotonic saline has the same osmolarity as body fluids.
What is the effect of hypotonic saline on osmolarity?
It lowers the overall osmolarity in all compartments
Hypotonic saline introduces more water than salts, leading to dilution.
Fill in the blank: The total body water is divided into _______ and _______ fluid compartments.
intracellular; extracellular
Approximately two-thirds of body water is intracellular, while one-third is extracellular.
What happens to the volume of extracellular fluid when hypotonic saline is administered?
It increases, and some water may shift into the intracellular compartment
This occurs because the osmolarity of the extracellular fluid is decreased.
What happens to osmolarity when a greater proportion of water than salts is added to a system?
Osmolarity of the system decreases
This occurs because the addition of more water dilutes the concentration of solutes.
What is the expected effect on intracellular fluid when hypotonic saline is administered?
Water moves into the intracellular fluid compartment
This movement occurs to balance osmolarity between compartments.
What is the osmolarity of cells before the addition of hypotonic saline?
300 mOsm/L
This value represents normal osmolarity for human cells.
What is the effect of administering .45% saline on osmolarity?
Reduces overall osmolarity and expands both intra and extracellular fluid compartments
.45% saline is considered hypotonic.
What happens when hypertonic saline (3% saline) is added to a system?
Overall osmolarity of the system is elevated
This occurs because more salts are added than water.
What is the primary consequence of adding hypertonic saline to the extracellular fluid?
It pulls pre-existing water from inside the cells
This movement occurs to balance osmolarity between the extracellular fluid and intracellular fluid.
Fill in the blank: The solution .45% saline is considered _______.
hypotonic
Hypotonic solutions have a lower concentration of solutes compared to the intracellular environment.
Fill in the blank: The osmolarity of extracellular fluid after adding hypotonic saline is expected to be _______.
250 mOsm/L
This reflects a dilution effect from the added water.
True or False: Water will move across the cell wall until osmolarity is balanced on both sides.
True
This is a fundamental principle of osmotic balance in cells.
