Fasting plasma glucose is 110 mg/dL in a man with type 2 diabetes reviewed at the NCD clinic 3 months after empagliflozin was added to metformin, yet his urine dipstick shows glucose 3+. He has no symptoms, eGFR is 85 mL/min/1.73 m2, and HbA1c has fallen from 8.6% to 7.2%. He has had one episode of genital candidiasis, and he asks whether the sugar in his urine means the diabetes is worse. How has his renal glucose titration curve changed?

Threshold and Tm both fall, so glucose spills at normal levels

Threshold rises, so less glucose is excreted

Unchanged; the urine glucose is secreted by the collecting duct

Splay is abolished while the threshold stays the same

In the paediatric emergency room, a child with severe dehydration from gastroenteritis is given a 20 mL/kg bolus of Ringer lactate. Bedside echocardiography allows the left ventricular pressure-volume loop to be estimated before and after the bolus; contractility and arterial resistance do not change. How does the loop change after the bolus?

Wider loop; EDV and stroke volume rise

Steeper end-systolic line; ESV falls

Taller loop; ESV rises and stroke volume falls

Physiology graphs, curves and clinical data

27 NEET-PG practice questions on Physiology graphs, curves and clinical data, part of Physiology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Easy
In a nerve conduction study, the rapid upstroke of each motor axon's action potential is due mainly to which ion movement?
1. ACalcium influx
2. BChloride influx
3. CSodium influx
4. DPotassium efflux
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Answer: C · Sodium influx
When the membrane reaches threshold, voltage-gated sodium channels open rapidly and sodium rushes in down its electrochemical gradient, driving the membrane towards the sodium equilibrium potential. The channels then inactivate, and delayed opening of potassium channels causes repolarisation and the after-hyperpolarisation.
- A: Calcium influx drives the upstroke in SA node and smooth muscle, not in nerve axons.
- B: Chloride movement stabilises the resting potential and does not cause the spike.
- D: Potassium efflux causes repolarisation.
Remember this
The nerve action potential upstroke is sodium influx; repolarisation is potassium efflux.
Question 2 · Medium
Cord blood of a term newborn delivered at a CHC has a P50 of 19 mmHg, compared with 27 mmHg in the mother's blood. Regarding the oxygen dissociation curve: 1. Fetal haemoglobin shifts it to the left. 2. Carbon monoxide shifts it to the left. 3. A rise in red cell 2,3-BPG shifts it to the left. 4. Hypothermia shifts it to the left. Which statements are correct?
1. A1, 2, 3 and 4
2. B2, 3 and 4 only
3. C1 and 3 only
4. D1, 2 and 4 only
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Answer: D · 1, 2 and 4 only
Fetal haemoglobin (alpha2 gamma2) binds 2,3-BPG poorly, so it has a higher affinity and a lower P50, helping the fetus take oxygen from maternal blood. Carbon monoxide and a fall in temperature also shift the curve left. A rise in 2,3-BPG, as at altitude or in anaemia, shifts the curve right and aids unloading.
- A: Statement 3 is false, so all four cannot be correct.
- B: Statement 1 is true and statement 3 is false.
- C: Statement 3 is false and statements 2 and 4 are true.
Remember this
HbF, CO, cold, alkalosis and low 2,3-BPG shift the dissociation curve left; raised 2,3-BPG shifts it right.
Question 3 · Hard
Fasting plasma glucose is 110 mg/dL in a man with type 2 diabetes reviewed at the NCD clinic 3 months after empagliflozin was added to metformin, yet his urine dipstick shows glucose 3+. He has no symptoms, eGFR is 85 mL/min/1.73 m2, and HbA1c has fallen from 8.6% to 7.2%. He has had one episode of genital candidiasis, and he asks whether the sugar in his urine means the diabetes is worse. How has his renal glucose titration curve changed?
1. AThreshold rises, so less glucose is excreted
2. BUnchanged; the urine glucose is secreted by the collecting duct
3. CSplay is abolished while the threshold stays the same
4. DThreshold and Tm both fall, so glucose spills at normal levels
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Answer: D · Threshold and Tm both fall, so glucose spills at normal levels
SGLT2 in the early proximal tubule normally reabsorbs about 90% of filtered glucose. Blocking it lowers the tubular maximum and the renal threshold, roughly from 180 mg/dL to well below the normal fasting level, so glucose appears in urine even when plasma glucose is normal. This glycosuria is the intended effect, removing about 60-80 g of glucose a day, and does not mean poor control.
- A: The threshold falls, not rises, with an SGLT2 inhibitor.
- B: Glucose is not secreted; it is filtered and not reabsorbed.
- C: The main change is a lower threshold and Tm, not removal of splay.
Remember this
SGLT2 inhibitors lower the renal threshold and Tm for glucose, causing glycosuria at normal plasma glucose.
Question 4 · Medium
In the paediatric emergency room, a child with severe dehydration from gastroenteritis is given a 20 mL/kg bolus of Ringer lactate. Bedside echocardiography allows the left ventricular pressure-volume loop to be estimated before and after the bolus; contractility and arterial resistance do not change. How does the loop change after the bolus?
1. ASteeper end-systolic line; ESV falls
2. BWider loop; EDV and stroke volume rise
3. CNarrower loop; EDV falls
4. DTaller loop; ESV rises and stroke volume falls
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Answer: B · Wider loop; EDV and stroke volume rise
A fluid bolus raises preload, so the diastolic filling point moves to the right along the end-diastolic pressure-volume curve. With contractility and afterload unchanged, the ventricle ejects to about the same end-systolic point, so the loop becomes wider and stroke volume increases.
- A: A steeper end-systolic line with lower ESV is the effect of a positive inotrope.
- C: A narrower loop with lower EDV follows loss of preload, such as haemorrhage.
- D: A taller loop with higher ESV and smaller stroke volume is the effect of raised afterload.
Remember this
More preload widens the PV loop to the right with a larger stroke volume; the end-systolic line is unchanged.
Question 5 · Medium
In the physiotherapy department, a strength-duration curve is plotted for the facial muscles of a patient with Bell palsy. The minimum current that excites the muscle with a very long pulse is 4 mA. The therapist then measures chronaxie. Chronaxie is the shortest pulse duration that excites the muscle with which current?
1. ATwice the rheobase, here 8 mA
2. BEqual to the rheobase, 4 mA
3. CFour times the rheobase, 16 mA
4. DHalf the rheobase, 2 mA
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Answer: A · Twice the rheobase, here 8 mA
Rheobase is the smallest current that excites tissue when the stimulus lasts indefinitely. Chronaxie is the duration needed at twice the rheobase, here 8 mA, and it is a measure of excitability. Denervated muscle has a much longer chronaxie and a curve shifted to the right, so serial curves help follow nerve recovery.
- B: The current equal to rheobase defines utilisation time, not chronaxie.
- C: Chronaxie is defined at twice, not four times, the rheobase.
- D: Half the rheobase cannot excite the tissue at any duration.
Remember this
Chronaxie is the pulse duration needed at twice the rheobase; it lengthens in denervated muscle.
Question 6 · Easy
A flow-volume loop from a chronic smoker with breathlessness on exertion shows a reduced peak expiratory flow followed by a concave, scooped-out expiratory limb; the inspiratory limb is normal in shape. Which pattern is this?
1. ARestrictive lung disease
2. BObstructive airway disease
3. CVariable extrathoracic obstruction
4. DFixed upper airway obstruction
Answer and explanation in LearnFree account
Question 7 · Hard
Two patients in the medical ICU are compared. Patient A, with COPD, has haemoglobin 15 g/dL, SaO2 80% and PaO2 45 mmHg. Patient B, with severe iron deficiency, has haemoglobin 7 g/dL, SaO2 98% and PaO2 95 mmHg. Both have the same cardiac output. Using CaO2 = 1.34 x Hb x SaO2 + 0.003 x PaO2, which patient has the lower arterial oxygen content, and about how much is it?
1. APatient A, about 16 mL/dL
2. BPatient B, about 13 mL/dL
3. CPatient A, about 12 mL/dL
4. DPatient B, about 9.5 mL/dL
Answer and explanation in LearnFree account
Question 8 · Medium
Ankle capillary data in a child with nephrotic syndrome (serum albumin 1.8 g/dL) and pitting oedema: capillary hydrostatic pressure 30 mmHg, interstitial hydrostatic pressure -2 mmHg, plasma oncotic pressure 14 mmHg, interstitial oncotic pressure 3 mmHg. Using Starling's equation (reflection coefficient taken as 1), what is the net filtration pressure?
1. A17 mmHg outward
2. B43 mmHg outward
3. C11 mmHg inward
4. D21 mmHg outward
Answer and explanation in LearnFree account
Question 9 · Hard
A pressure-volume loop from a patient with a collapsing pulse (BP 170/50 mmHg) shows a very large end-diastolic volume of 260 mL and end-systolic volume of 120 mL. Ventricular volume begins to rise during what should be isovolumic relaxation, before the mitral valve opens, while the isovolumic contraction phase is preserved. Peak systolic pressure is high. Which lesion explains this loop?
1. AMitral stenosis
2. BAortic regurgitation
3. CMitral regurgitation
4. DDilated cardiomyopathy
Answer and explanation in LearnFree account
Question 10 · Medium
On an arterial pressure trace in the ICU, which event does the dicrotic notch on the downstroke mark?
1. APeak of rapid ventricular ejection
2. BOpening of the mitral valve
3. CClosure of the aortic valve
4. DOpening of the aortic valve
Answer and explanation in LearnFree account
Question 11 · Easy
Spirometry: FEV1 1.4 L (52% predicted), FVC 2.9 L (88% predicted), FEV1/FVC 0.48. What pattern is this?
1. ARestrictive defect
2. BObstructive defect
3. CMixed defect
4. DNormal spirometry
Answer and explanation in LearnFree account
Question 12 · Medium
In the cardiac ICU, dobutamine is started for a patient with low cardiac output after myocardial infarction, and serial left ventricular pressure-volume loops are recorded at the same preload. 1. The end-systolic pressure-volume relationship becomes steeper. 2. End-systolic volume falls. 3. Stroke volume rises. 4. The end-diastolic pressure-volume curve shifts upward. Which changes are expected?
1. A1, 2 and 3 only
2. B1, 2, 3 and 4
3. C2, 3 and 4 only
4. D1 and 4 only
Answer and explanation in LearnFree account
Question 13 · Medium
After rapid transfusion of two units of blood to a trauma patient in casualty, mean systemic filling pressure is estimated to rise from 7 to 10 mmHg, while resistance to venous return is unchanged. On Guyton's venous return curve, what happens?
1. AThe curve shifts right, parallel to the original
2. BThe slope flattens with no shift
3. CThe curve shifts left, parallel to the original
4. DThe curve rotates upward around the same intercept
Answer and explanation in LearnFree account
Question 14 · Medium
Nerve conduction studies in a young man with 10 days of ascending weakness and areflexia after a bout of diarrhoea: median motor conduction velocity 24 m/s (normal above 50), prolonged distal motor latency, conduction block in the forearm and prolonged F-wave latencies, with near-normal compound muscle action potential amplitude at the wrist. Which process do these results show?
1. AAnterior horn cell loss
2. BAxonal degeneration
3. CNeuromuscular junction failure
4. DDemyelination of peripheral nerves
Answer and explanation in LearnFree account
Question 15 · Medium
Why is the oxygen dissociation curve of myoglobin hyperbolic, unlike the sigmoid curve of haemoglobin?
1. AIt binds 2,3-BPG more strongly
2. BIt has one haem and no cooperativity
3. CIt has four haems that bind cooperatively
4. DIt lacks the proximal histidine
Answer and explanation in LearnFree account
Question 16 · Easy
During cardiopulmonary exercise testing of a cyclist, the haemoglobin-oxygen dissociation curve of venous blood from the working leg is shifted, with the P50 rising from 27 to 31 mmHg. Which change in the active muscle produces this shift?
1. ARising pH as lactate is washed out
2. BFalling local temperature
3. CFalling red cell 2,3-BPG
4. DRising PCO2, H+ and temperature
Answer and explanation in LearnFree account
Question 17 · Medium
Static pressure-volume curves of the lungs from two patients are compared with a normal curve in the pulmonary function laboratory. Patient A's curve is steeper and shifted upward and to the left; Patient B's curve is flatter and shifted downward and to the right. Which pair of diagnoses fits?
1. AA emphysema, B pulmonary fibrosis
2. BA pulmonary fibrosis, B emphysema
3. CA asthma, B emphysema
4. DA pulmonary oedema, B emphysema
Answer and explanation in LearnFree account
Question 18 · Medium
Lung function in a stone-cutter from Rajasthan with 10 years of dust exposure and breathlessness: FVC 52% predicted, FEV1 58% predicted, FEV1/FVC 0.86, total lung capacity 60% predicted and DLCO 45% predicted. His chest radiograph shows nodules in the upper zones. How are these results best interpreted?
1. AObstructive defect with air trapping
2. BRestrictive defect from chest wall disease
3. CRestrictive defect with impaired gas transfer
4. DNormal lung function for his age
Answer and explanation in LearnFree account
Question 19 · Medium
Pressure data from cardiac catheterisation in a man with exertional syncope and an ejection systolic murmur: peak left ventricular systolic pressure 210 mmHg while peak aortic systolic pressure is 120 mmHg. The pressure-volume loop is tall, with a slightly reduced stroke volume and a steep diastolic limb. Which condition fits these data best?
1. ASystemic hypertension
2. BChronic aortic regurgitation
3. CSevere aortic stenosis
4. DNon-obstructive hypertrophic cardiomyopathy
Answer and explanation in LearnFree account
Question 20 · Medium
Rescued from a smoke-filled room in a house fire in Delhi, a woman is drowsy with a headache. On 40% oxygen, the pulse oximeter reads SpO2 98% and arterial PaO2 is 102 mmHg, but co-oximetry shows carboxyhaemoglobin 28%. How does carbon monoxide change the oxygen dissociation curve of her blood?
1. AShifts it right and lowers the maximum content
2. BShifts it left and lowers the maximum content
3. CShifts it right without changing content
4. DLeaves its position and shape unchanged
Answer and explanation in LearnFree account
Question 21 · Hard
Repetitive nerve stimulation is done in a heavy smoker with 3 months of proximal leg weakness, dry mouth and depressed reflexes that briefly improve after exercise. The resting compound muscle action potential is small at 1.2 mV; after 10 seconds of maximal voluntary contraction it rises to 3.6 mV. Slow stimulation at 3 Hz gives a decremental response. He has no ptosis or diplopia, and he becomes light-headed on standing. CT of the chest shows a hilar mass with enlarged mediastinal nodes. What is the mechanism of his weakness?
1. AAntibodies to muscle-specific kinase (MuSK)
2. BAntibodies to postsynaptic acetylcholine receptors
3. CAntibodies to presynaptic voltage-gated calcium channels
4. DToxin cleaving SNAP-25 in nerve terminals
Answer and explanation in LearnFree account
Question 22 · Medium
In the electrophysiology lab, the neurologist teaches residents how to read nerve conduction results. 1. Axonal neuropathy mainly reduces the amplitude of the compound action potentials. 2. In demyelination, amplitude falls more than conduction velocity. 3. Conduction block is a sign of axonal loss. 4. F waves are prolonged or absent in proximal demyelination. Which statements are correct?
1. A2 and 3 only
2. B1, 3 and 4 only
3. C1 and 4 only
4. D1, 2 and 4 only
Answer and explanation in LearnFree account
Question 23 · Hard
On the second day after a total thyroidectomy for a large multinodular goitre, a woman in the surgical ward has a hoarse, weak voice and noisy breathing that is worse when she breathes in, especially on exertion. Laryngoscopy shows both vocal cords lying near the midline and moving poorly. A flow-volume loop is obtained before planning further management. Which pattern is expected?
1. AFlattened inspiratory limb, normal expiratory limb
2. BBoth limbs flattened into a box shape
3. CScooped expiratory limb with normal inspiration
4. DFlattened expiratory limb, normal inspiratory limb
Answer and explanation in LearnFree account
Question 24 · Medium
A left ventricular pressure-volume loop recorded at cardiac catheterisation in a breathless patient shows no isovolumic contraction phase: volume begins to fall as soon as pressure starts rising, well before the aortic valve opens. End-diastolic volume is increased and the isovolumic relaxation limb is preserved. Which valve lesion explains this loop?
1. AMitral stenosis
2. BAortic stenosis
3. CMitral regurgitation
4. DAortic regurgitation
Answer and explanation in LearnFree account
Question 25 · Medium
Plotting urinary glucose excretion against plasma glucose during a glucose tolerance test in a diabetic patient, glucose first appears in the urine at a plasma level of about 180 mg/dL, but excretion rises in a straight line only above about 300-350 mg/dL. The curved part between these two levels is called splay. What explains it?
1. ASGLT2 saturates in all nephrons at once
2. BPlasma glucose is bound to albumin
3. CGlucose is secreted by the distal tubule
4. DNephrons differ in their glucose transport capacity
Answer and explanation in LearnFree account

2 more Physiology graphs, curves and clinical data questions

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Physiology graphs, curves and clinical data

In a nerve conduction study, the rapid upstroke of each motor axon's action potential is due mainly to which ion movement?

A flow-volume loop from a chronic smoker with breathlessness on exertion shows a reduced peak expiratory flow followed by a concave, scooped-out expiratory limb; the inspiratory limb is normal in shape. Which pattern is this?

On an arterial pressure trace in the ICU, which event does the dicrotic notch on the downstroke mark?

Spirometry: FEV1 1.4 L (52% predicted), FVC 2.9 L (88% predicted), FEV1/FVC 0.48. What pattern is this?

After rapid transfusion of two units of blood to a trauma patient in casualty, mean systemic filling pressure is estimated to rise from 7 to 10 mmHg, while resistance to venous return is unchanged. On Guyton's venous return curve, what happens?

Why is the oxygen dissociation curve of myoglobin hyperbolic, unlike the sigmoid curve of haemoglobin?

During cardiopulmonary exercise testing of a cyclist, the haemoglobin-oxygen dissociation curve of venous blood from the working leg is shifted, with the P50 rising from 27 to 31 mmHg. Which change in the active muscle produces this shift?

Static pressure-volume curves of the lungs from two patients are compared with a normal curve in the pulmonary function laboratory. Patient A's curve is steeper and shifted upward and to the left; Patient B's curve is flatter and shifted downward and to the right. Which pair of diagnoses fits?

Rescued from a smoke-filled room in a house fire in Delhi, a woman is drowsy with a headache. On 40% oxygen, the pulse oximeter reads SpO2 98% and arterial PaO2 is 102 mmHg, but co-oximetry shows carboxyhaemoglobin 28%. How does carbon monoxide change the oxygen dissociation curve of her blood?