29 Questions
What percentage of the body is composed of water?
60%
Which of the following is NOT a regulated route of water loss?
Renal excretion
When the intake of water is greater than the loss of water, what is the resulting water balance?
Positive water balance
What is the osmolarity of urine when the kidneys conserve water?
1200 mOsm/kg H2O
What percentage of the body is composed of intracellular fluid (ICF)?
40%
When the kidneys conserve water, what is the resulting urine volume?
0.5 L/day
What percentage change in body fluid osmolarity can alter the secretion of ADH?
1%
Where are the osmoreceptors located that sense changes in body fluid osmolarity?
Anterior hypothalamus
What happens to circulating ADH levels when secretion is inhibited?
They are reduced to zero within minutes
What is the normal range of set point for plasma osmolarity in individuals?
275-290 mOsm/kg H2O
What can affect the set point of the ADH secretion system?
Changes in blood volume and blood pressure
What is the primary function of the kidneys in terms of water balance?
Maintaining a constant solute load in body fluids
What is the main mechanism by which the kidneys regulate urine concentration and volume?
Countercurrent multiplication and urea recycling
What is the osmotic gradient in the interstitial fluid of the kidneys?
300 mOsm to 1200 mOsm/Kg H2O
What is the role of antidiuretic hormone (ADH) in the kidneys?
Facilitating water reabsorption in the collecting ducts
What is the solute load of body fluids that the kidneys aim to maintain?
300 mOsm/L
What is the name of the process by which the kidneys concentrate urine?
Countercurrent multiplication
What is the primary function of the thick ascending limb of the loop of Henle?
To decrease the osmolarity of the tubular fluid and increase the osmolarity of the surrounding interstitial fluid
What is the osmolarity of the new fluid that enters the descending limb of the loop of Henle?
300 mOsm/L
What is the result of the 'single effect' in the countercurrent multiplier?
The osmolarity of the ascending limb decreases, and the osmolarity of the descending limb increases
What is the purpose of the countercurrent multiplier in the loop of Henle?
To create a gradient of osmolarity along the loop of Henle
What happens to the high osmolarity fluid in the descending limb as a result of the flow of tubular fluid?
It is pushed down towards the bend of the loop of Henle
What happens to the osmolarity of the interstitial fluid and descending limb in LoH Step 3?
It increases
What is the direction of water flow in the descending limb of the loop of Henle?
From the tubular fluid to the surrounding interstitial fluid
What is the osmolarity of the new fluid that enters the descending limb from the PT in LoH Step 4?
300 mOsm/L
What is the constant difference in filtrate concentration between the 2 limbs of the LoH?
200 mOsm
What happens to the fluid in the ascending limb as a result of the fluid shift in LoH Step 4?
It is pushed downward towards the bend of the LoH
What is the role of the NaCl pumps in the ascending limb?
To create a constant difference in filtrate concentration between the 2 limbs of the LoH
What is the result of the fluid shift in LoH Step 4 on the gradient of osmolarity?
It increases
This quiz covers the role of kidneys in regulating water balance, the functions and mechanism of action of ADH, and renal mechanisms for concentrating and diluting urine. It also explores the distribution of water in the body and its regulation.
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