Foundations of Medicine
Case Q&A Study Resource
Table of Contents
Introduction ............................................................................................................ 2
Module 1: Renal & Fluid Balance ............................................................................... 2
Module 2: GI & Nutrition ......................................................................................... 10
Module 3: Cardiovascular & Respiratory .................................................................. 17
Module 4: Musculoskeletal & Neuro ........................................................................ 24
Module 5: Immunology & Pathology......................................................................... 30
Module 6: Ethics, Law & Population Health .............................................................. 36
Exam Prep Tips ...................................................................................................... 42
Conclusion ............................................................................................................ 43
,Introduction
During my university career, my preferred study method involved active recall and question and
answer in a case-based format, which is why this resource is designed this way. By using a "Triple-Step
Discovery" method (Scenario, Hint, and Deep-Dive) the material moves away from passive reading and
mimics the cognitive load of a real exam, forcing the brain to "reach" for the answer before the logic is
revealed. To use this resource effectively, first read the clinical scenario carefully. If stuck, refer to the hint
to narrow the focus to the correct physiological system or anatomical landmark before finally reviewing
the deep-dive. This deep-dive section is crucial as it highlights the foundational logic and the clinical
application, which is exactly how UQ integrates their assessments. Finally, the high-yield "exam tips" at
the end of the manual can be used for a rapid-fire review in the 48 hours leading up to exams to solidify
must-know facts.
Module 1: Renal & Fluid Balance
Scenario 1: The Metabolic Cost of Reabsorption
The Case: A 74-year-old female with chronic hypertension is admitted with signs of acute-on-chronic
renal failure. Laboratory results show a significant drop in GFR. You are asked to consider which part of
her nephron is currently under the most metabolic stress as it attempts to maintain homeostatic solute
reabsorption despite decreased perfusion.
The Question: Which specific segment of the nephron is characterized by the highest density of
mitochondria and the most significant oxygen consumption per gram of tissue?
The HINT: Recall your histology and transport kinetics. Which segment is responsible for the "bulk"
reabsorption (approx. 65-70%) of filtered sodium, water, and nearly 100% of glucose? High-volume active
transport requires massive amounts of ATP.
The Deep-Dive Overview:
• The Answer: The Proximal Convoluted Tubule (PCT).
• Foundational Logic: The PCT cells are packed with mitochondria to power the Na+/K+ ATPase
pumps on the basolateral membrane. This creates the electrochemical gradient necessary for
secondary active transport (e.g., SGLT2 for glucose).
• Clinical Logic: Because the PCT is so metabolically "expensive," it is the first area to fail during
ischemia. This leads to Acute Tubular Necrosis (ATN), where epithelial cells slough off and form
"muddy brown casts" in the urine—a classic UQ exam "trigger" phrase.
Scenario 2: G-Protein Signaling and Water Retention
The Case: A patient is diagnosed with Central Diabetes Insipidus following a head injury. They are
producing large volumes of dilute urine because their posterior pituitary is no longer secreting
Vasopressin (ADH). You decide to treat them with Desmopressin (a synthetic ADH analogue).
The Question: Upon binding to the V2 receptor in the collecting duct, which secondary messenger
pathway is activated to trigger the insertion of Aquaporin-2 channels?
The HINT: ADH V2 receptors are G-protein coupled receptors (GPCRs). Does this specific pathway
involve the cleavage of PIP2 (IP3/DAG) or the activation of Adenylyl Cyclase?
,The Deep-Dive Overview:
• The Answer: Gs → Adenylyl Cyclase → cAMP → Protein Kinase A (PKA).
• Foundational Logic: This is a textbook example of GPCR signaling. Binding to the Gs-coupled V2
receptor activates Adenylyl Cyclase, which converts ATP to cAMP. PKA then phosphorylates
vesicles containing Aquaporin-2, causing them to fuse with the apical membrane.
• Clinical Logic: In Nephrogenic Diabetes Insipidus, the hormone is present, but the receptor or
signaling pathway is broken (often due to Lithium toxicity). Understanding the signaling pathway
helps you differentiate between a "brain" problem (Central) and a "kidney" problem
(Nephrogenic).
Scenario 3: The RAAS Cascade and Pressure Regulation
The Case: A 28-year-old female is found to have a significant narrowing of her right renal artery (Renal
Artery Stenosis). Her blood pressure is 170/105 mmHg. Her kidneys perceive this low flow as "low blood
pressure" and activate a compensatory hormonal cascade.
The Question: Which cell type in the kidney senses this drop in perfusion pressure and releases the initial
enzyme required to start the RAAS cascade?
The HINT: These cells are modified smooth muscle cells located in the afferent arteriole. They work in
tandem with the macula densa of the distal tubule.
The Deep-Dive Overview:
• The Answer: Juxtaglomerular (JG) Cells.
• Foundational Logic: The Juxtaglomerular Apparatus (JGA) is the kidney's "thermostat" for
pressure. JG cells release Renin in response to: 1. Decreased stretch (baroreception), 2.
Sympathetic stimulation (beta1), or 3. Decreased NaCl delivery sensed by the macula densa.
• Clinical Logic: Renin converts Angiotensinogen to Angiotensin I. The "logic" trap in exams is the
role of Angiotensin II, which causes potent vasoconstriction and stimulates Aldosterone
release from the adrenal cortex to increase sodium/water reabsorption.
Scenario 4: Osmotic Shifts and Tonicity
The Case: An endurance runner collapses after a marathon. In an attempt to rehydrate, they consumed
10 liters of pure water over 4 hours without electrolyte replacement. They are now confused and having
seizures. Laboratory tests show a serum sodium of 118 mmol/L (Severe Hyponatremia).
The Question: In this state of "Hypotonic Overhydration," what is the net movement of water relative to
the patient's brain cells, and what is the primary risk?
The HINT: Water always follows the higher concentration of solutes (Osmosis). If the blood is "dilute"
(hypotonic) compared to the "salty" interior of the cells, where will the water go?
The Deep-Dive Overview:
• The Answer: Water moves into the cells; Risk of Cerebral Edema.
, • Foundational Logic: This demonstrates the difference between Osmolarity (total solutes) and
Tonicity (effect on cell volume). Because the ECF is now hypotonic relative to the ICF, water
moves via osmosis into the neurons, causing them to swell.
• Clinical Logic: This is Exercise-Associated Hyponatremia (EAH). The critical management rule
is to avoid correcting sodium too quickly. If you "dry out" the brain too fast with hypertonic saline,
you risk Osmotic Demyelination Syndrome (formerly Central Pontine Myelinolysis).
Scenario 5: The Filtration Barrier
The Case: A 10-year-old boy presents with "cola-colored" urine and facial swelling (edema) two weeks
after a sore throat. A urinalysis shows significant protein (Proteinuria) and Red Blood Cell casts.
The Question: Which component of the glomerular filtration barrier is responsible for the "charge-based"
exclusion of proteins like albumin?
The HINT: The barrier consists of the fenestrated endothelium, the basement membrane, and the
podocytes. Which of these is coated in negatively charged heparan sulfate?
The Deep-Dive Overview:
• The Answer: The Glomerular Basement Membrane (GBM).
• Foundational Logic: The filtration barrier is both a size filter and a charge filter. The GBM is rich
in polyanionic glycoproteins that repel negatively charged proteins (like Albumin).
• Clinical Logic: In Post-Streptococcal Glomerulonephritis (PSGN), immune complexes get
trapped in this barrier, causing inflammation (Nephritic Syndrome). This destroys the charge
barrier, allowing RBCs and protein to leak into the urine. RBC casts are the definitive sign of
"glomerular" bleeding.
Scenario 6: The Acid-Base "Golden Rule"
The Case: A 19-year-old male with Type 1 Diabetes is brought to the ED by his roommates. He is lethargic,
breathing deeply and rapidly (Kussmaul breathing), and his breath has a fruity odor. An Arterial Blood Gas
(ABG) shows: pH 7.15, PaCO2 25 mmHg, and HCO3- 12 mEq/L.
The Question: What is the primary acid-base disturbance, and what is the physiological purpose of his
rapid breathing?
The HINT: Check the pH first—is it high or low? Then look at the Bicarbonate (HCO3-). If both the pH and
Bicarb are moving in the same direction, the problem is metabolic. Why would the lungs try to blow off
CO2 in this state?
The Deep-Dive Overview:
• The Answer: Metabolic Acidosis with Respiratory Compensation.
• Foundational Logic: This is Diabetic Ketoacidosis (DKA). The accumulation of ketoacids
consumes Bicarbonate buffers. According to the Henderson-Hasselbalch equation, a drop in
HCO3- necessitates a drop in CO2 to keep the ratio (and thus pH) as stable as possible.
Case Q&A Study Resource
Table of Contents
Introduction ............................................................................................................ 2
Module 1: Renal & Fluid Balance ............................................................................... 2
Module 2: GI & Nutrition ......................................................................................... 10
Module 3: Cardiovascular & Respiratory .................................................................. 17
Module 4: Musculoskeletal & Neuro ........................................................................ 24
Module 5: Immunology & Pathology......................................................................... 30
Module 6: Ethics, Law & Population Health .............................................................. 36
Exam Prep Tips ...................................................................................................... 42
Conclusion ............................................................................................................ 43
,Introduction
During my university career, my preferred study method involved active recall and question and
answer in a case-based format, which is why this resource is designed this way. By using a "Triple-Step
Discovery" method (Scenario, Hint, and Deep-Dive) the material moves away from passive reading and
mimics the cognitive load of a real exam, forcing the brain to "reach" for the answer before the logic is
revealed. To use this resource effectively, first read the clinical scenario carefully. If stuck, refer to the hint
to narrow the focus to the correct physiological system or anatomical landmark before finally reviewing
the deep-dive. This deep-dive section is crucial as it highlights the foundational logic and the clinical
application, which is exactly how UQ integrates their assessments. Finally, the high-yield "exam tips" at
the end of the manual can be used for a rapid-fire review in the 48 hours leading up to exams to solidify
must-know facts.
Module 1: Renal & Fluid Balance
Scenario 1: The Metabolic Cost of Reabsorption
The Case: A 74-year-old female with chronic hypertension is admitted with signs of acute-on-chronic
renal failure. Laboratory results show a significant drop in GFR. You are asked to consider which part of
her nephron is currently under the most metabolic stress as it attempts to maintain homeostatic solute
reabsorption despite decreased perfusion.
The Question: Which specific segment of the nephron is characterized by the highest density of
mitochondria and the most significant oxygen consumption per gram of tissue?
The HINT: Recall your histology and transport kinetics. Which segment is responsible for the "bulk"
reabsorption (approx. 65-70%) of filtered sodium, water, and nearly 100% of glucose? High-volume active
transport requires massive amounts of ATP.
The Deep-Dive Overview:
• The Answer: The Proximal Convoluted Tubule (PCT).
• Foundational Logic: The PCT cells are packed with mitochondria to power the Na+/K+ ATPase
pumps on the basolateral membrane. This creates the electrochemical gradient necessary for
secondary active transport (e.g., SGLT2 for glucose).
• Clinical Logic: Because the PCT is so metabolically "expensive," it is the first area to fail during
ischemia. This leads to Acute Tubular Necrosis (ATN), where epithelial cells slough off and form
"muddy brown casts" in the urine—a classic UQ exam "trigger" phrase.
Scenario 2: G-Protein Signaling and Water Retention
The Case: A patient is diagnosed with Central Diabetes Insipidus following a head injury. They are
producing large volumes of dilute urine because their posterior pituitary is no longer secreting
Vasopressin (ADH). You decide to treat them with Desmopressin (a synthetic ADH analogue).
The Question: Upon binding to the V2 receptor in the collecting duct, which secondary messenger
pathway is activated to trigger the insertion of Aquaporin-2 channels?
The HINT: ADH V2 receptors are G-protein coupled receptors (GPCRs). Does this specific pathway
involve the cleavage of PIP2 (IP3/DAG) or the activation of Adenylyl Cyclase?
,The Deep-Dive Overview:
• The Answer: Gs → Adenylyl Cyclase → cAMP → Protein Kinase A (PKA).
• Foundational Logic: This is a textbook example of GPCR signaling. Binding to the Gs-coupled V2
receptor activates Adenylyl Cyclase, which converts ATP to cAMP. PKA then phosphorylates
vesicles containing Aquaporin-2, causing them to fuse with the apical membrane.
• Clinical Logic: In Nephrogenic Diabetes Insipidus, the hormone is present, but the receptor or
signaling pathway is broken (often due to Lithium toxicity). Understanding the signaling pathway
helps you differentiate between a "brain" problem (Central) and a "kidney" problem
(Nephrogenic).
Scenario 3: The RAAS Cascade and Pressure Regulation
The Case: A 28-year-old female is found to have a significant narrowing of her right renal artery (Renal
Artery Stenosis). Her blood pressure is 170/105 mmHg. Her kidneys perceive this low flow as "low blood
pressure" and activate a compensatory hormonal cascade.
The Question: Which cell type in the kidney senses this drop in perfusion pressure and releases the initial
enzyme required to start the RAAS cascade?
The HINT: These cells are modified smooth muscle cells located in the afferent arteriole. They work in
tandem with the macula densa of the distal tubule.
The Deep-Dive Overview:
• The Answer: Juxtaglomerular (JG) Cells.
• Foundational Logic: The Juxtaglomerular Apparatus (JGA) is the kidney's "thermostat" for
pressure. JG cells release Renin in response to: 1. Decreased stretch (baroreception), 2.
Sympathetic stimulation (beta1), or 3. Decreased NaCl delivery sensed by the macula densa.
• Clinical Logic: Renin converts Angiotensinogen to Angiotensin I. The "logic" trap in exams is the
role of Angiotensin II, which causes potent vasoconstriction and stimulates Aldosterone
release from the adrenal cortex to increase sodium/water reabsorption.
Scenario 4: Osmotic Shifts and Tonicity
The Case: An endurance runner collapses after a marathon. In an attempt to rehydrate, they consumed
10 liters of pure water over 4 hours without electrolyte replacement. They are now confused and having
seizures. Laboratory tests show a serum sodium of 118 mmol/L (Severe Hyponatremia).
The Question: In this state of "Hypotonic Overhydration," what is the net movement of water relative to
the patient's brain cells, and what is the primary risk?
The HINT: Water always follows the higher concentration of solutes (Osmosis). If the blood is "dilute"
(hypotonic) compared to the "salty" interior of the cells, where will the water go?
The Deep-Dive Overview:
• The Answer: Water moves into the cells; Risk of Cerebral Edema.
, • Foundational Logic: This demonstrates the difference between Osmolarity (total solutes) and
Tonicity (effect on cell volume). Because the ECF is now hypotonic relative to the ICF, water
moves via osmosis into the neurons, causing them to swell.
• Clinical Logic: This is Exercise-Associated Hyponatremia (EAH). The critical management rule
is to avoid correcting sodium too quickly. If you "dry out" the brain too fast with hypertonic saline,
you risk Osmotic Demyelination Syndrome (formerly Central Pontine Myelinolysis).
Scenario 5: The Filtration Barrier
The Case: A 10-year-old boy presents with "cola-colored" urine and facial swelling (edema) two weeks
after a sore throat. A urinalysis shows significant protein (Proteinuria) and Red Blood Cell casts.
The Question: Which component of the glomerular filtration barrier is responsible for the "charge-based"
exclusion of proteins like albumin?
The HINT: The barrier consists of the fenestrated endothelium, the basement membrane, and the
podocytes. Which of these is coated in negatively charged heparan sulfate?
The Deep-Dive Overview:
• The Answer: The Glomerular Basement Membrane (GBM).
• Foundational Logic: The filtration barrier is both a size filter and a charge filter. The GBM is rich
in polyanionic glycoproteins that repel negatively charged proteins (like Albumin).
• Clinical Logic: In Post-Streptococcal Glomerulonephritis (PSGN), immune complexes get
trapped in this barrier, causing inflammation (Nephritic Syndrome). This destroys the charge
barrier, allowing RBCs and protein to leak into the urine. RBC casts are the definitive sign of
"glomerular" bleeding.
Scenario 6: The Acid-Base "Golden Rule"
The Case: A 19-year-old male with Type 1 Diabetes is brought to the ED by his roommates. He is lethargic,
breathing deeply and rapidly (Kussmaul breathing), and his breath has a fruity odor. An Arterial Blood Gas
(ABG) shows: pH 7.15, PaCO2 25 mmHg, and HCO3- 12 mEq/L.
The Question: What is the primary acid-base disturbance, and what is the physiological purpose of his
rapid breathing?
The HINT: Check the pH first—is it high or low? Then look at the Bicarbonate (HCO3-). If both the pH and
Bicarb are moving in the same direction, the problem is metabolic. Why would the lungs try to blow off
CO2 in this state?
The Deep-Dive Overview:
• The Answer: Metabolic Acidosis with Respiratory Compensation.
• Foundational Logic: This is Diabetic Ketoacidosis (DKA). The accumulation of ketoacids
consumes Bicarbonate buffers. According to the Henderson-Hasselbalch equation, a drop in
HCO3- necessitates a drop in CO2 to keep the ratio (and thus pH) as stable as possible.
