Question 1

A particular epithelium has a paracellular (between the cells) pathway permeable to water and chloride. In order to enhance the net movement of NaCl and water from apical to basolateral portions of the cell, the epithelium needs: A) Basolateral Na⁺K⁺-ATPase, basolateral K⁺ channels, and apical Na⁺ channels B) Apical Na⁺K⁺-ATPase, apical K⁺ channels, and basolateral Na⁺ channels C) Basolateral Na⁺K⁺-ATPase, apical K⁺channels, and basolateral Na⁺ channels D) Apical Na⁺K⁺-ATPase, basolateral K⁺ channels, and apical Na⁺ channels E) Basolateral Na⁺K⁺-ATPase, basolateral K⁺ channels, and basolateral Na⁺ channels

Accepted Answer

The correct choice is A because it describes the necessary components for effective NaCl and water transport across epithelial cells: a basolateral Na+/K+-ATPase to actively pump Na+ out of the cell (creating a low intracellular Na+ concentration that drives Na+ entry at the apical side), basolateral K+ channels to allow K+ to recycle back into the extracellular space (maintaining the electrochemical gradient), and apical Na+ channels to allow Na+ entry into the cell from the apical side. This setup creates a net movement of NaCl from the apical to the basolateral side, with water following osmotically through the paracellular pathway.

Question 2

Some tumor cells have a large number of Cl^- channels on the plasma membrane. This makes the Cl^-permeability higher than that of any other ion and therefore: A) Causes the cell to swell when suspended in isotonic NaCl B) Causes the cell to shrink when suspended in isotonic NaCl C) Increases the steady state intracellular osmolality D) Decreases the steady state intracellular osmolality E) Causes the membrane potential to be near the equilibrium potential for Cl^-

Accepted Answer

The high Cl^- permeability means that the membrane potential is likely to be close to the equilibrium potential for Cl^-, as the ion with the highest permeability has the greatest influence on the membrane potential.

Question 3

An epithelial cell layer bathed in physiological saline solution on both apical and basolateral surfaces starts out in a steady state in which there is constant absorption of Na⁺, Cl^-, and H₂O. The addition of ouabain to the basolateral side will cause: A) Intracellular Na⁺ to rise and intracellular K⁺ to remain constant B) Intracellular Na⁺ to fall and intracellular K⁺ to rise C) Intracellular Na⁺ to rise and intracellular K⁺ to fall D) Intracellular Na⁺ to remain constant and intracellular K⁺ to fall E) Intracellular Na⁺ to remain constant and intracellular K⁺ to remain constant

Accepted Answer

Ouabain inhibits the Na+/K+ ATPase pump, leading to an accumulation of Na+ inside the cell and a decrease in K+ inside the cell as the pump can no longer exchange intracellular Na+ for extracellular K+.

Question 4

A 36-year-old male patient with a recent head injury complains of polyuria. You suspect central diabetes insipidus. How could you confirm the diagnosis?
A) Restrict water intake and treat with insulin and see if urinary volume is decreased.
B) Restrict water intake and treat with angiotensin II and see if urinary volume is decreased.
C) Restrict water intake and treat with arginine vasopressin (AVP) and see if urinary volume declines.
D) Restrict water intake and treat with a loop diuretic to determine if urinary flow rates decrease.
E) Compare urinary production rates following consumption of 3 L of water and 3 L of isotonic saline to determine whether they differ.

Accepted Answer

To confirm a diagnosis of central diabetes insipidus, a water deprivation test followed by administration of arginine vasopressin (AVP) can be used. If the patient has central diabetes insipidus, their ability to concentrate urine will be impaired due to a lack of AVP, but will improve after administration of AVP.

Question 5

A 30-year-old woman complains of extreme fatigue following even mild exercise. These symptoms become worse throughout the day. You diagnose this patient with myasthenia gravis (MG). In most patients with MG autoantibodies cause a decrease in:
A) Presynaptic action potential threshold
B) Postsynaptic action potential threshold
C) Postsynaptic (endplate) potential
D) Excitation-contraction (E-C) coupling
E) Neurotransmitter release from the nerve terminal

Accepted Answer

Myasthenia gravis is an autoimmune disorder characterized by the production of autoantibodies against the acetylcholine receptors at the neuromuscular junction, leading to a decrease in the postsynaptic (endplate) potential. This impairs the ability of the muscle to contract in response to nerve impulses.

Question 6

Given the following data from a patient - urine output 1.5 L/day; plasma creatinine 1.0 mg/dL; urinary creatinine 1.2 mg/mL; plasma phosphate 0.002 mEq/mL; urinary phosphate 0.05 mEq/mL - what can you reliably conclude about the renal handling of phosphate?
A) There is net secretion of phosphate.
B) There is net reabsorption of phosphate.
C) Phosphate is neither secreted nor reabsorbed.
D) Phosphate is fractionally filtered.
E) The extraction ratio of phosphate is greater than 1.

Accepted Answer

The renal handling of phosphate primarily involves its reabsorption from the filtrate back into the bloodstream. Given the data, with a higher concentration of phosphate in the urine compared to plasma, it indicates that although phosphate is filtered, a significant portion is reabsorbed, as the body typically conserves phosphate due to its importance in various physiological processes. The fact that there is still phosphate present in the urine does not indicate net secretion or that it is neither secreted nor reabsorbed; rather, it shows that while phosphate is filtered, the majority is reabsorbed, which is a characteristic behavior of renal phosphate handling.

Question 7

A 44 year-old male presents to the emergency department with severe back pain radiating to the left flank. A radiological exam reveals a kidney stone partially blocking the ureter of one kidney. Based on your knowledge of renal physiology, which of the following statements is correct?
A) The patient will have problems with salt and water balance due to a loss of 50% of renal function.
B) Glomerular filtration rate (GFR) in the affected kidney will decrease.
C) Urinary flow will be reduced by approximately 50%.
D) Hydrostatic pressure in the tubules will be decreased.
E) Renal failure will occur.

Accepted Answer

The presence of a kidney stone partially blocking the ureter can lead to increased pressure in the renal tubules upstream of the blockage, which can reduce the glomerular filtration rate (GFR) in the affected kidney due to the reduced ability of the kidney to filter blood effectively.

Question 8

Which statement is true about a 5 kg infant and his 50 kg mother?
A) The rate (mL/day) of insensible water loss is ten times as high in the mother as in the infant.
B) The water turnover rate (% total body water [TBW]/day) is the same in the infant and the mother.
C) The water turnover rate (%TBW/day) is higher in the mother than in the infant.
D) The mother has a TBW of about 42 kg.
E) The mother has an intracellular water of about 20 kg.

Accepted Answer

The answer of Which statement is true about a 5...

Question 9

Lambert-Eaton Syndrome (LES) is similar to myasthenia gravis. In LES, which of the following is most affected during neuromuscular transmission? A) The driving force for Ca²⁺ influx in the nerve terminal B) The synthesis of acetylcholine (ACh) in the nerve terminal C) The release of ACh from the nerve terminal D) The degradation of ACh in the synaptic cleft E) The response to ACh in the muscle membrane

Accepted Answer

Lambert-Eaton Syndrome (LES) primarily affects the release of acetylcholine (ACh) from the nerve terminal, leading to muscle weakness. This is due to antibodies against presynaptic calcium channels, which are crucial for ACh release.

Question 10

A 25-year-old female medical student from out of state wants to drive home over the 4th of July holiday. She hates to use public facilities and would prefer to minimize her urinary flow rate. Unfortunately, the air conditioning in her car is broken so she knows that she will have to consume 2-3 L of fluids to replace that lost due to sweating. What is her best choice to drink during the 8-hours to result in a minimum of rest room breaks?
A) Bottled water
B) Coffee
C) Sports drinks
D) Soda
E) Sweetened tea

Accepted Answer

Sports drinks are the best choice in this scenario because they contain electrolytes (like sodium and potassium) which help to retain fluid in the body, thus reducing urine output. This is in contrast to diuretics like coffee and soda, which increase urine production, and to plain water or sweetened tea, which do not contain electrolytes to aid in fluid retention.

Quiz 1: Introduction

A particular epithelium has a paracellular (between the cells) pathway permeable to water and chloride. In order to enhance the net movement of NaCl and water from apical to basolateral portions of the cell, the epithelium needs:

Some tumor cells have a large number of Cl^- channels on the plasma membrane. This makes the Cl^-permeability higher than that of any other ion and therefore:

An epithelial cell layer bathed in physiological saline solution on both apical and basolateral surfaces starts out in a steady state in which there is constant absorption of Na⁺, Cl^-, and H₂O. The addition of ouabain to the basolateral side will cause:

A 36-year-old male patient with a recent head injury complains of polyuria. You suspect central diabetes insipidus. How could you confirm the diagnosis?

A 30-year-old woman complains of extreme fatigue following even mild exercise. These symptoms become worse throughout the day. You diagnose this patient with myasthenia gravis (MG) . In most patients with MG autoantibodies cause a decrease in:

Given the following data from a patient - urine output 1.5 L/day; plasma creatinine 1.0 mg/dL; urinary creatinine 1.2 mg/mL; plasma phosphate 0.002 mEq/mL; urinary phosphate 0.05 mEq/mL - what can you reliably conclude about the renal handling of phosphate?

A 44 year-old male presents to the emergency department with severe back pain radiating to the left flank. A radiological exam reveals a kidney stone partially blocking the ureter of one kidney. Based on your knowledge of renal physiology, which of the following statements is correct?

Which statement is true about a 5 kg infant and his 50 kg mother?

Lambert-Eaton Syndrome (LES) is similar to myasthenia gravis. In LES, which of the following is most affected during neuromuscular transmission?