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Questions and Answers
Which system is the primary control for fluid and electrolyte balance?
Which system is the primary control for fluid and electrolyte balance?
Respiratory compensation for fluid and electrolyte balance is faster than renal compensation.
Respiratory compensation for fluid and electrolyte balance is faster than renal compensation.
True (A)
What role does urea play in urine concentration?
What role does urea play in urine concentration?
Urea increases interstitial osmolarity in the kidney's medulla.
High osmolarity corresponds to __________ water volume.
High osmolarity corresponds to __________ water volume.
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Match the following components related to the loop of Henle with their functions:
Match the following components related to the loop of Henle with their functions:
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What effect does vasopressin have on the collecting duct's permeability to water?
What effect does vasopressin have on the collecting duct's permeability to water?
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A decrease in atrial stretch stimulates vasopressin release from the posterior pituitary.
A decrease in atrial stretch stimulates vasopressin release from the posterior pituitary.
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What is the primary function of aquaporins in the collecting duct?
What is the primary function of aquaporins in the collecting duct?
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As plasma osmolarity rises, the body releases more vasopressin to retain water and attempts to lower osmolarity by increasing _____ absorption.
As plasma osmolarity rises, the body releases more vasopressin to retain water and attempts to lower osmolarity by increasing _____ absorption.
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Match the following components with their functions in the vasopressin signaling pathway:
Match the following components with their functions in the vasopressin signaling pathway:
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Flashcards
Osmolarity and Urine Volume
Osmolarity and Urine Volume
High osmolarity means low water volume and less urine production. Low osmolarity means high water volume and more urine production.
Countercurrent Multiplier
Countercurrent Multiplier
The countercurrent multiplier in the loop of Henle actively transports Na+, Cl-, and K+ out of the nephron, creating high osmolarity in the medulla's interstitial fluid.
Thick Ascending Limb
Thick Ascending Limb
The thick ascending limb of the loop of Henle actively pumps ions out, contributing to the high osmolarity in the medulla.
Vasa Recta
Vasa Recta
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Urea's Role
Urea's Role
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Vasopressin's Role
Vasopressin's Role
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Vasopressin Release Triggers
Vasopressin Release Triggers
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Vasopressin's Graded Effect
Vasopressin's Graded Effect
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Where are Osmoreceptors Located?
Where are Osmoreceptors Located?
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Vasopressin Action on Principal Cells
Vasopressin Action on Principal Cells
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Study Notes
Fluid and Electrolyte Homeostasis
- Renal, respiratory, and cardiovascular systems control fluid and electrolyte balance
- Renal compensation is slower than respiratory and cardiovascular compensation
- Renal/kidneys are controlled by endocrine and neuroendocrine systems
- Respiratory and cardiovascular systems are controlled by neural systems
- High osmolarity = low water volume → less urine production
- Low osmolarity = high water volume → more urine production
- Kidneys are the primary route for ion and water excretion
Countercurrent Multiplier in the Loop of Henle
- Creates high osmolarity in the interstitial fluid of the medulla
- Active transport of Na+, Cl-, and K+ out of the nephron occurs in the thick ascending limb
- Necessary for making concentrated urine as filtrate flows through the collecting duct
- Pumping ions establishes a gradient for other substances to passively follow
- Vasa recta capillaries act as a countercurrent exchanger, removing water from the nephron to prevent medulla dilution
- Urea plays a significant role in increasing interstitial osmolarity
Water Balance and Vasopressin
- Vasopressin (AVP/ADH) controls collecting duct permeability to water in a graded fashion
- Increase in vasopressin causes aquaporins to be inserted into apical membranes of collecting duct
- Graded effect matches urine concentration to body's water volume needs
- As plasma osmolarity increases (from dehydration or solute intake), the body releases more vasopressin to retain water
- In the absence of vasopressin, water permeability in the collecting duct is nearly zero
Renin-Angiotensin-Aldosterone System (RAAS)
- Aldosterone is released in response to low blood pressure by the renin-angiotensin system
- Low blood pressure stimulates granular cells in the kidneys to release renin
- Renin converts angiotensinogen to angiotensin I, then to angiotensin II (ANG II) by ACE
- ANG II stimulates aldosterone secretion and has other effects on blood pressure
- Three mechanisms for low blood pressure to initiate renin production: increasing sympathetic activity, granular cells' response to stretch, and low glomerular filtration rate (GFR) causing changes in NaCl transport
Natriuretic Peptides
- Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are released in response to increased blood volume
- These peptides enhance Na+ excretion and urinary water loss
- They increase glomerular filtration rate (GFR), inhibit tubular reabsorption of NaCl (salt), and inhibit the release of renin, aldosterone, and vasopressin
- ANP is released in response to high blood pressure
Potassium Balance
- Potassium homeostasis maintains plasma K+ concentrations within a narrow range
- Hyperkalemia (too much potassium) can lead to cardiac arrhythmias
- Hypokalemia (too little potassium) can cause muscle weakness, and respiratory muscle failure
Acid-Base Balance
- Carbon dioxide (CO2) from respiration is a major source of acid
- CO2 combines with water to form H+ and bicarbonate (HCO3-) with the assistance of carbonic anhydrase
- Buffers, ventilation, and kidneys help maintain pH through compensation of minute-to-minute pH shifts
Respiratory Compensation for pH Changes
- Respiration is the first response to pH changes in the body
- Chemoreceptors in the carotid and aortic bodies monitor changes in pH and stimulate the respiratory control center in the medulla to adjust breathing rate and depth, helping to control CO2 levels in the blood, which in turn affects the pH
Renal Compensation for pH Changes
- Kidneys compensate for pH changes by regulating the secretion and reabsorption of hydrogen (H+) and bicarbonate (HCO3-) ions in the urine
- Intercalated cells in the collecting ducts are responsible for fine pH regulation, especially in response to acidosis or alkalosis.
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Description
This quiz explores the mechanisms behind fluid and electrolyte balance in the body, emphasizing the roles of the renal, respiratory, and cardiovascular systems. It highlights the importance of renal compensation and the countercurrent multiplier system in the Loop of Henle for urine concentration.
