#!/usr/bin/env python3
"""Generate a compact reasoning-question PDF with examiner-highlighted key lines."""
from reportlab.lib.pagesizes import A4
from reportlab.lib.units import mm
from reportlab.lib.styles import getSampleStyleSheet, ParagraphStyle
from reportlab.lib.enums import TA_LEFT
from reportlab.platypus import SimpleDocTemplate, Paragraph, Spacer, Table, TableStyle, PageBreak
from reportlab.lib import colors

styles = getSampleStyleSheet()
h1 = ParagraphStyle('h1', parent=styles['Heading1'], fontSize=14, spaceAfter=8, textColor=colors.HexColor('#B34700'))
qstyle = ParagraphStyle('q', parent=styles['Normal'], fontSize=9.5, leading=12, spaceBefore=6, fontName='Helvetica-Bold')
astyle = ParagraphStyle('a', parent=styles['Normal'], fontSize=9.5, leading=12, spaceAfter=4, leftIndent=8)

DATA = [
("GENERAL PHYSIOLOGY", [
("Rate of diffusion if surface area of membrane increases?",
 "Rate of diffusion is <b>directly proportional to surface area</b> (Fick's Law) - larger area, faster diffusion."),
("Decrease in plasma protein - effect on fluid distribution?",
 "↓ plasma protein → <b>↓ plasma oncotic pressure</b> → fluid shifts from vascular to interstitial space → <b>edema</b>."),
("Large amount of salt ingested - effect on intracellular volume?",
 "↑ ECF osmolarity → water moves out of cells → <b>intracellular fluid volume decreases (cell shrinkage)</b>."),
("How do gap junctions facilitate cell-cell communication?",
 "Connexons form direct channels between cytoplasm of adjacent cells → <b>allow direct passage of ions/small molecules, enabling electrical & chemical coupling</b>."),
("Effect of increased extracellular K+ on RMP?",
 "↓ K+ gradient across membrane → <b>RMP becomes less negative (partial depolarization)</b>."),
("Role of Na-K pump in maintaining RMP?",
 "3Na+ out : 2K+ in per ATP → <b>maintains the ionic gradients that generate RMP</b>; also contributes a small electrogenic component."),
("Threshold potential and its relation to RMP?",
 "Threshold (~-55mV) is the depolarization level at which <b>voltage-gated Na+ channels open enough for a self-propagating action potential</b>; the gap between RMP (-70mV) and threshold sets excitability."),
]),
("BLOOD", [
("Deficiency of Factor VIII - effect on coagulation?",
 "Impaired <b>intrinsic pathway → delayed fibrin formation, prolonged aPTT</b> → Hemophilia A, joint/muscle bleeds."),
("↓ RBC count (anemia) - effect on O2 delivery?",
 "↓ Hb → <b>↓ O2 carrying capacity → tissue hypoxia</b>, compensatory tachycardia/tachypnea."),
("Bleeding disorder affecting platelet function - effect on coagulation?",
 "Defective primary hemostasis → <b>prolonged Bleeding Time, normal Clotting Time</b> - mucocutaneous bleeding."),
("Why blood does not clot in vivo?",
 "Smooth endothelium + <b>natural anticoagulants (heparin, antithrombin III, prostacyclin/NO)</b> prevent platelet activation and clotting factor activation."),
("Mechanisms of anemia reversal after gastrectomy?",
 "Correction of underlying cause (e.g. <b>H. pylori/achlorhydria-related malabsorption improved, or iron/B12 supplementation started</b>) restores erythropoiesis - though gastrectomy itself can also cause anemia via loss of intrinsic factor/acid."),
("How does opsonization aid phagocytosis?",
 "Antibody/C3b <b>coats the pathogen and binds Fc/complement receptors on phagocytes</b> → enhanced recognition and engulfment."),
("Why is Aspirin given in myocardial infarction?",
 "Irreversibly inhibits <b>COX-1 → blocks thromboxane A2 → prevents platelet aggregation</b>, limiting clot extension."),
("Why can Dicumarol not be used as an in vitro anticoagulant?",
 "It acts by <b>inhibiting hepatic synthesis of vitamin-K dependent factors (II,VII,IX,X)</b> - needs a living liver, has no direct effect on blood already drawn."),
("Why is clotting time prolonged in Vit K deficiency/liver disease?",
 "↓ synthesis of <b>factors II, VII, IX, X (vitamin K dependent, liver-made)</b> → prolonged PT/CT."),
("Why is BT prolonged but CT normal in thrombocytopenic purpura?",
 "Platelet defect impairs only <b>primary hemostasis (platelet plug) → BT ↑</b>; coagulation cascade (secondary hemostasis) is intact → CT normal."),
("Why does reticulocyte count increase after Vitamin B12 therapy?",
 "Corrected DNA synthesis allows <b>marrow to resume erythropoiesis - immature reticulocytes are released ('reticulocyte crisis')</b>."),
("Why is B12 given parenterally in pernicious anemia?",
 "Autoimmune loss of parietal cells → <b>no intrinsic factor → oral B12 cannot be absorbed in ileum</b> - must bypass the gut."),
("Why is capillary blood Hct lower than actual blood Hct?",
 "<b>Plasma skimming</b> - axial streaming of RBCs in small vessels leaves relatively more plasma near the vessel wall/capillary entry."),
("Why does edema develop in hypoalbuminemia?",
 "↓ plasma oncotic pressure → <b>filtration exceeds reabsorption at capillaries → net fluid loss into interstitium</b>."),
("Why is there bleeding tendency in obstructive jaundice?",
 "No bile reaches gut → <b>impaired fat & Vitamin K absorption → deficiency of factors II,VII,IX,X</b>."),
("Why does bleeding occur in chronic liver disease?",
 "<b>↓ hepatic synthesis of clotting factors</b> + hypersplenism-related thrombocytopenia."),
("Why is PCV of venous blood greater than arterial?",
 "CO2 loading causes the <b>chloride/Hamburger shift - water enters RBCs</b>, slightly swelling them in venous blood."),
("Why does clot not spread beyond the injured vessel?",
 "<b>Circulating inhibitors (antithrombin III, protein C/S) and dilution/removal of activated factors by flowing blood</b> confine the clot; healthy endothelium releases prostacyclin."),
("Why is the first child usually normal in Rh-negative mother/Rh-positive fetus?",
 "Maternal <b>sensitization (anti-D IgG formation) mainly occurs at delivery</b> when fetal cells cross over - too late to affect the first child; subsequent pregnancies are at risk."),
("Why is stored blood unsuitable for transfusing WBCs/platelets?",
 "<b>WBCs and platelets lose viability/function rapidly on storage</b> (short shelf life) - stored blood is used mainly for RBCs."),
("Why is 'O' Rh-negative blood used in extreme emergency?",
 "It is the <b>universal donor - lacks A, B, and Rh(D) antigens</b>, minimizing risk of acute hemolytic transfusion reaction when cross-matching isn't possible."),
("Why do ABO incompatibilities rarely cause HDN?",
 "Naturally occurring anti-A/anti-B are mostly <b>IgM, which cannot cross the placenta</b>; fetal A/B antigen expression is also weak."),
]),
("GIT", [
("Effect of vagotomy on gastric acid secretion and motility?",
 "Loss of vagal ACh → <b>↓ cephalic-phase acid secretion and ↓ gastric motility (delayed emptying)</b>."),
("Effect of pancreatic insufficiency on digestion/absorption?",
 "↓ lipase/amylase/trypsin → <b>maldigestion of fat, carbs, protein → steatorrhea and malabsorption</b>."),
("Effect of impaired bile production on fat digestion?",
 "↓ bile salts → <b>failure of emulsification/micelle formation → fat malabsorption, steatorrhea</b>."),
("Effect of gastroparesis on postprandial blood sugar?",
 "Delayed gastric emptying → <b>delayed glucose absorption - early hypoglycemia risk, then late mismatched hyperglycemia</b>."),
("Effect of SIBO on nutrient absorption?",
 "Bacteria consume nutrients & deconjugate bile salts → <b>malabsorption, B12 deficiency, bloating/diarrhea</b>."),
("Effect of impaired CCK release?",
 "<b>↓ pancreatic enzyme secretion and ↓ gallbladder contraction</b> → fat maldigestion."),
("Effect of slowed intestinal motility (constipation) on absorption/microbiota?",
 "Prolonged transit → <b>favors bacterial overgrowth/fermentation</b> and alters water/nutrient reabsorption."),
("Why is postprandial alkaline tide seen after a heavy meal?",
 "Parietal cell H+ secretion into stomach is matched by <b>HCO3- entering blood via the basolateral Cl-/HCO3- exchanger</b> → transient blood/urine alkalinisation."),
("Why are stools bulky and clay-colored in obstructive jaundice?",
 "No bile reaches gut → <b>no stercobilin (pale/clay stool)</b>; undigested fat makes stool bulky and greasy."),
("Why does aptyalism raise dental caries risk?",
 "Loss of saliva's <b>antibacterial, buffering and mechanical-cleansing action</b> allows bacterial/acid overgrowth."),
("Why does steatorrhea occur in pancreatic insufficiency?",
 "<b>Lack of pancreatic lipase</b> leaves dietary fat undigested and passed in stool."),
("Why is vagally-mediated gastrin release not blocked by atropine?",
 "Vagal stimulation of G cells uses <b>GRP (gastrin-releasing peptide), not muscarinic ACh</b> - atropine blocks only muscarinic receptors."),
("Why is gastric mucosa resistant to autodigestion?",
 "<b>Mucus-bicarbonate barrier, tight epithelial junctions and rapid cell turnover</b> protect against HCl/pepsin."),
("Why does alcohol intoxication reduce if consumed with a fat-rich drink?",
 "Fat <b>delays gastric emptying → slower alcohol delivery/absorption</b> in the small intestine."),
("Why can duodenal ulcer be treated by vagotomy?",
 "Removing vagal ACh drive <b>reduces gastric acid secretion</b>."),
("Why does resection of a large ileal segment cause steatorrhea?",
 "Loss of the <b>enterohepatic circulation site for bile salt reabsorption</b> depletes the bile salt pool → impaired micelle formation."),
("Why is achlorhydria linked to iron-deficiency anemia?",
 "Gastric acid is needed to <b>convert dietary Fe3+ to the absorbable Fe2+ form</b>."),
("Why is Ranitidine/Omeprazole given in peptic ulcer?",
 "<b>H2-blocker/PPI reduce gastric acid secretion</b>, allowing the ulcer to heal."),
("Why is dizziness seen after a meal in a gastrectomised patient (dumping syndrome)?",
 "Hyperosmolar food rapidly enters jejunum → <b>fluid shifts into the gut lumen → hypovolemia and reactive hypoglycemia</b>."),
("Why does rapid changing movement cause vomiting?",
 "<b>Vestibular apparatus stimulation activates the vomiting centre via the CTZ</b>."),
("Why does chronic diarrhea cause severe hypokalemia?",
 "Intestinal secretions are <b>K+ rich - large ongoing loss in watery stool</b>."),
("Why are appreciable feces still passed during prolonged starvation?",
 "<b>Sloughed intestinal cells, bacteria and secretions</b> continue to form residue even without food intake."),
("How and why does most bile reach the circulation rather than being excreted?",
 "<b>Bile salts are reabsorbed in the terminal ileum (enterohepatic circulation)</b> and recycled; only a small fraction is lost in feces."),
("Why is Misoprostol given with NSAIDs in arthritis treatment?",
 "It is a <b>PGE1 analogue that restores the mucosal protection (mucus/bicarbonate) lost due to NSAID-induced COX/prostaglandin inhibition</b>."),
("Why is glucose not formed by salivary amylase action on starch alone?",
 "Amylase only cleaves <b>α-1,4 bonds to maltose/dextrins, not down to monosaccharide glucose</b> - needs further intestinal enzymes."),
]),
("RESPIRATORY SYSTEM", [
("Effect of a blocked airway on breathing rate and blood gases?",
 "↓ ventilation → <b>hypoxia + hypercapnia → reflex ↑ respiratory rate/effort</b>, cyanosis if severe."),
("Effect of pneumothorax on breathing rate and blood O2?",
 "Lung collapse (loss of negative intrapleural pressure) → <b>↓ ventilation → hypoxemia, ↑ respiratory rate</b>."),
("Why does breathing rate increase during exercise?",
 "↑ CO2/lactic acid production → <b>stimulates central & peripheral chemoreceptors</b> (plus joint/muscle afferents)."),
("Why do people at high altitude experience hypoxia?",
 "<b>↓ atmospheric pO2 → ↓ alveolar and arterial pO2</b> despite compensatory hyperventilation."),
("Why do scuba divers breathe compressed air?",
 "To <b>match increased ambient water pressure and keep the lungs/airways inflated</b> against the surrounding pressure."),
("Why is intrapleural pressure always negative/subatmospheric?",
 "Opposing recoils - <b>lung elastic recoil pulls inward, chest wall recoils outward</b> - create a subatmospheric pleural pressure that keeps the lung expanded."),
("Why does pulmonary TB affect the apex of the lung first?",
 "Apex has the <b>highest V/Q ratio (relatively more air, less blood/O2 delivery)</b> favoring aerobic bacilli, plus poor lymphatic drainage."),
("Why is the expiratory phase longer than the inspiratory phase?",
 "Inspiration is active (muscular); <b>expiration is a passive, slower process driven only by elastic recoil</b>."),
("Why is bronchial asthma a disease of expiratory obstruction?",
 "Bronchoconstriction/mucus narrow airways further during expiration as <b>intrathoracic pressure rises and compresses airways</b>, trapping air."),
("Why is a high V/P (V/Q) ratio observed at the apices of the lungs?",
 "Gravity gives the apex the <b>lowest perfusion but relatively preserved ventilation</b> → high V/Q."),
("Why is compliance of lungs+thorax together less than lung alone?",
 "Total compliance follows <b>1/C(total) = 1/C(lung) + 1/C(thorax)</b> - always less than either component alone."),
("Why is arterial pO2 less than alveolar pO2?",
 "Due to <b>physiological shunt and V/Q mismatch (A-a gradient)</b>."),
("Why is the O2-Hb dissociation curve sigmoid in shape?",
 "<b>Cooperative binding - each O2 bound to a heme subunit increases affinity of the remaining subunits</b> (allosteric change)."),
("Why does myoglobin act as a temporary O2 storehouse?",
 "Its <b>hyperbolic curve/high O2 affinity lets it load O2 at rest and release it only when local pO2 falls very low</b> (during exercise)."),
("Why is blood an ideal vehicle for O2 transport?",
 "<b>Hemoglobin raises O2 carrying capacity ~70-fold</b> compared to simple dissolved O2 in plasma."),
("Why do central chemoreceptors respond only to abrupt pCO2 changes?",
 "CO2 crosses the BBB and <b>generates H+ in CSF that stimulates the receptors</b>; they adapt/reset with chronic (sustained) changes."),
("Why are respiratory chemoreceptors not stimulated in anemia or CO poisoning?",
 "Peripheral chemoreceptors sense <b>dissolved pO2, not total O2 content/Hb saturation</b> - which is normal in these conditions."),
("Why does mild hypoxia stimulate but severe hypoxia depress respiration?",
 "Mild hypoxia excites peripheral chemoreceptors, but <b>severe hypoxia directly depresses the medullary respiratory neurons</b>, overriding the stimulatory drive."),
("Why is ventilation unaffected until inspired pO2 falls below 60 mmHg?",
 "The <b>peripheral chemoreceptor response curve is flat until this threshold</b>, then rises steeply."),
("How does CO2 increase pulmonary ventilation primarily via central chemoreceptors?",
 "CO2 diffuses into CSF → forms H2CO3 → <b>H+ stimulates central chemoreceptors</b> - the most potent respiratory drive."),
("Why does apnea occur after voluntary hyperventilation?",
 "<b>pCO2 falls below the apneic threshold</b>, removing the main respiratory drive."),
("Why is cyanosis not seen in anemic hypoxia?",
 "Cyanosis needs ≥5g/dL of <b>deoxygenated Hb in absolute terms - total Hb is too low to reach that amount</b> even if % saturation is low."),
("Why is cyanosis a common occurrence in hypoxic hypoxia?",
 "Arterial desaturation <b>raises absolute deoxygenated Hb above the 5g/dL threshold</b>."),
("Why can histotoxic hypoxia not cause cyanosis?",
 "Tissues fail to use O2 but <b>blood remains fully oxygenated (normal SaO2)</b>, so deoxy-Hb stays low."),
("Why are babies of diabetic mothers prone to IRDS?",
 "Fetal hyperinsulinemia <b>delays surfactant (lecithin) synthesis by type II pneumocytes</b>."),
("Why does systemic venous (pulmonary arterial) blood have lower pO2 than pulmonary venous blood?",
 "It is <b>deoxygenated blood returning from tissues</b>; oxygenation only occurs after gas exchange in the alveoli."),
("Why do venous RBCs have a higher hematocrit than arterial?",
 "<b>Chloride/Hamburger shift - water enters RBCs with CO2 loading</b>, causing slight cell swelling in venous blood."),
("Why does a lesion in inspiratory neurons not abolish respiratory activity?",
 "<b>Redundant medullary/pontine respiratory centres</b> (DRG, VRG, pneumotaxic/apneustic) provide backup rhythmicity."),
("Why can't a rise in blood H+ activate central chemoreceptors directly?",
 "The <b>blood-brain barrier is relatively impermeable to H+</b>; only CO2 crosses freely to generate H+ locally in CSF."),
("Why is an O2-N2 mixture (not pure O2) used in SCUBA?",
 "Pure O2 at depth (high pressure) causes <b>O2 toxicity</b>; N2 dilution prevents this."),
("How does sitting up relieve orthopnea?",
 "Gravity <b>pools venous blood in the legs, reducing venous return and pulmonary congestion</b>."),
("Why is headache experienced in an overcrowded room?",
 "<b>CO2 accumulation causes cerebral vasodilation</b>, producing headache."),
("How does severe joint pain occur in decompression sickness?",
 "Rapid ascent → <b>dissolved nitrogen comes out of solution as gas bubbles (Boyle's law)</b> in blood/joint tissues - 'the bends'."),
]),
("CARDIOVASCULAR SYSTEM", [
("Effect of SA node damage on heart rate?",
 "<b>AV node takes over as pacemaker</b> → slower junctional rhythm (~40-60 bpm)."),
("Effect of AV node block on cardiac conduction?",
 "<b>Complete heart block - atria and ventricles beat independently</b>, ventricles driven by their own slow intrinsic pacemaker (~30-40 bpm)."),
("Effect of sudden ↑ in peripheral resistance on BP?",
 "↑ afterload → <b>↑ BP (BP = CO × TPR)</b>."),
("Effect of significant ↓ in cardiac output on tissue perfusion?",
 "<b>↓ tissue perfusion → hypotension/organ hypoperfusion (shock)</b>."),
("Effect of sudden ↑ sympathetic tone on HR/BP?",
 "<b>↑ HR, ↑ contractility, vasoconstriction → ↑ BP</b>."),
("Effect of sudden ↑ parasympathetic tone on HR/BP?",
 "<b>Vagal action on SA node → ↓ HR → ↓ CO → tends to ↓ BP</b>."),
("Why do HR and BP increase during exercise?",
 "<b>Sympathetic activation ↑ CO</b>; local vasodilation in muscle is offset by overall rise in cardiac output driving systolic BP up."),
("Why does blood flow to skeletal muscle increase during exercise?",
 "<b>Local metabolites (CO2, K+, adenosine, lactate) cause vasodilation</b>, overriding sympathetic vasoconstriction - active hyperemia."),
("Why does pulmonary vascular resistance increase at high altitude?",
 "<b>Hypoxic pulmonary vasoconstriction</b> - a reflex unique to the pulmonary circuit (opposite of systemic vessels)."),
("Why is bradycardia seen in raised intracranial tension?",
 "Part of the <b>Cushing reflex - hypertension triggers baroreceptor-mediated reflex bradycardia</b>."),
("Why is tachycardia usually seen with old age?",
 "<b>↓ vagal tone/baroreceptor sensitivity</b> and stiffer vessels reduce resting parasympathetic dominance."),
("What is physiological hypertrophy of the LV and why does it occur?",
 "<b>Adaptive compensatory response to sustained ↑ workload</b> (e.g. athletic training) - increases pumping capacity without pathology."),
("Why are heart sounds not produced during valve opening?",
 "Normal opening is a <b>low-resistance, laminar flow event (silent)</b>; sounds arise only from turbulence/vibration at valve closure."),
("Why is myocardium well perfused during diastole?",
 "During systole, the <b>contracting myocardium compresses intramural coronary vessels</b>, so most coronary flow (especially LV) occurs in diastole."),
("Why does fainting occur during emotions (vasovagal syncope)?",
 "Sudden <b>↑ vagal tone + peripheral vasodilation → ↓ BP → ↓ cerebral perfusion</b>."),
("Why are thin, delicate capillaries less prone to rupture?",
 "<b>Law of Laplace - wall tension is proportional to radius</b>; capillaries have a very small radius, keeping wall tension low."),
("Why does a dilated heart have to do more work than a non-dilated heart?",
 "By <b>Laplace's law, a larger radius needs greater wall tension to generate the same pressure</b> - less efficient, higher O2 demand."),
("Why are veins called capacitance vessels?",
 "<b>Highly distensible - hold ~60-70% of total blood volume with minimal pressure change</b>, acting as a blood reservoir."),
("Why does variation in arteriolar diameter markedly affect systolic BP?",
 "<b>Arterioles are the principal resistance vessels</b> - changes in their tone directly alter total peripheral resistance and BP."),
("Why can cardiac muscle not be tetanized / show no fatigue?",
 "<b>Long refractory period (near equal to contraction duration) prevents summation</b>; continuous rich coronary blood supply prevents fatigue."),
("Why do atrial and ventricular muscles not show autorhythmicity?",
 "They <b>lack the pacemaker ('funny current') property</b> - only specialized nodal/conducting tissue generates spontaneous impulses."),
("Why should systolic BP first be measured by the palpatory method?",
 "To <b>detect and avoid missing readings due to the auscultatory gap</b> before proceeding with the cuff/stethoscope."),
("Why does heart rate increase during inspiration (sinus arrhythmia)?",
 "<b>↓ vagal tone during inspiration + stretch-induced SA node firing from ↑ venous return</b>."),
("Why is stroke volume increased during exercise?",
 "<b>↑ venous return (Frank-Starling law) + sympathetic-driven ↑ contractility</b>."),
("Why does baroreceptor stimulation at the carotid sinus alter heart rate?",
 "↑ pressure on the sinus <b>increases baroreceptor firing → vagal reflex → ↓ heart rate and BP</b> (carotid sinus massage/syncope)."),
("How does extracellular Ca2+ influence force of cardiac contraction?",
 "Cardiac muscle depends on <b>Ca2+ influx via L-type channels to trigger Ca2+-induced Ca2+ release from the SR</b> - more extracellular Ca2+ means a stronger contraction."),
("Why do cold clammy skin and rapid pulse occur in hypovolemic shock?",
 "<b>Sympathetic vasoconstriction (skin) + reflex tachycardia</b> compensate for ↓ blood volume/cardiac output."),
("Why should a patient in shock not be covered with a blanket?",
 "Warming causes <b>peripheral vasodilation, diverting blood from vital organs and worsening hypotension</b>."),
]),
("RENAL SYSTEM", [
("Effect of sudden ↓ GFR on urine production?",
 "<b>↓ urine output (oliguria)</b> and retention of nitrogenous waste."),
("Effect of significantly ↑ renal blood flow on GFR/urine output?",
 "<b>↑ GFR and transient ↑ urine output</b>, limited by renal autoregulation."),
("Effect of excessive ADH on water reabsorption/urine concentration?",
 "<b>Aquaporin-2 insertion in collecting duct → ↑ water reabsorption</b> → small volume, highly concentrated urine (risk of dilutional hyponatremia)."),
("Effect of significantly ↓ aldosterone on Na+/K+ handling?",
 "<b>↓ Na+ reabsorption and ↓ K+ secretion</b> in DCT/collecting duct → hyponatremia and hyperkalemia."),
("Effect of renal tubule damage on electrolyte/acid-base balance?",
 "Impaired reabsorption/secretion → <b>electrolyte imbalance and metabolic acidosis</b> (↓ HCO3- reabsorption, ↓ H+ secretion)."),
("Why does renal blood flow increase on a high-sodium diet?",
 "<b>↓ sympathetic/renin-angiotensin tone, ↑ ANP → renal vasodilation</b>, promoting natriuresis."),
("Why does aldosterone secretion increase on a low-sodium diet?",
 "↓ blood volume/BP activates <b>renin-angiotensin system - Angiotensin II stimulates aldosterone release</b> to conserve Na+."),
("Why does urine pH decrease during acidosis?",
 "Kidneys <b>excrete excess H+ as titratable acid and NH4+</b> to compensate for systemic acidosis."),
("Why does blood pressure increase during renal failure?",
 "<b>Na+/water retention (↑ volume) plus renin-angiotensin activation</b>."),
("Why does acid-base balance change in renal failure?",
 "Failure to <b>excrete H+ and regenerate HCO3- → metabolic acidosis</b>."),
("Why does the renal medulla play a crucial role in concentrating urine?",
 "It maintains the <b>hyperosmotic interstitial gradient via countercurrent multiplication (Loop of Henle)</b> that draws water from the collecting duct."),
("Why does the PCT have a high rate of O2 consumption?",
 "<b>Active Na-K-ATPase transport for bulk reabsorption</b> of Na+, glucose and amino acids demands large amounts of ATP."),
("Why is high resistance offered to blood flow in the efferent arteriole?",
 "Its <b>smaller diameter than the afferent arteriole maintains glomerular capillary pressure</b> needed for filtration."),
("Why does medullary blood flow not show autoregulation?",
 "Flow is deliberately kept <b>low and sluggish to preserve the medullary osmotic gradient</b> (prevent washout by vasa recta)."),
("Why does renal failure develop in persons with poor renal perfusion?",
 "Prolonged ischemia → <b>acute tubular necrosis</b> (pre-renal progressing to intrinsic renal failure)."),
("How does chronic renal disease produce anemia?",
 "<b>↓ erythropoietin production by the kidney → ↓ RBC production</b>."),
("Why is the predicted renal threshold for glucose higher than the actual value?",
 "Due to <b>'splay' - nephrons have varying Tm, so some start spilling glucose before the calculated average threshold</b> is reached."),
("How does Angiotensin II help the body respond to hypovolemia?",
 "<b>Vasoconstriction (↑BP), stimulates aldosterone & ADH release, stimulates thirst</b> - restores volume and BP."),
("How does increased ANP secretion lead to natriuresis?",
 "<b>Inhibits Na+ reabsorption in collecting duct, inhibits renin/aldosterone, dilates afferent arteriole (↑GFR)</b> - promotes Na+/water excretion."),
("How is hemoglobin an important buffer in the body?",
 "<b>Histidine imidazole groups on globin buffer H+</b> generated from CO2 (as carbonic acid) in tissues and lungs."),
("Why is there increased frequency of micturition during nervousness?",
 "<b>Sympathetic/anxiety-driven ↑ detrusor sensitivity</b> increases urge/frequency without necessarily increasing volume."),
("How does a high protein diet increase the kidney's concentrating ability?",
 "↑ <b>urea production adds to medullary interstitial hyperosmolarity</b>, aiding passive water reabsorption."),
("Why does albuminuria occur in nephrotic syndrome?",
 "<b>Damaged glomerular filtration barrier (podocytes/basement membrane)</b> becomes abnormally permeable to protein."),
("Why is there splay in the glucose titration curve?",
 "<b>Nephron-to-nephron variability in Tm for glucose</b> - some nephrons spill glucose before others reach true Tm."),
("Why is hyperosmolarity in the medullary interstitium important for concentrating urine?",
 "It is the <b>driving force for passive water reabsorption</b> from the collecting duct via countercurrent multiplication."),
("Why does a plateau phase occur in the cystometrogram?",
 "<b>Detrusor accommodation/relaxation</b> allows the bladder to fill with only a gradual rise in pressure (compliance)."),
("Why is the renal medulla more exposed to hypoxic damage than the cortex?",
 "It receives a <b>much lower share of renal blood flow (~1-2%) relative to its high metabolic (transport) activity</b>."),
("Why is PAH used to determine renal blood flow?",
 "PAH is <b>almost completely cleared from plasma in one pass (filtered + secreted)</b> → its clearance approximates renal plasma flow (÷ (1-Hct) for RBF)."),
]),
]

def build():
    doc = SimpleDocTemplate("Physiology_Reasoning_QA.pdf", pagesize=A4,
                             topMargin=14*mm, bottomMargin=14*mm, leftMargin=16*mm, rightMargin=16*mm)
    story = []
    title_style = ParagraphStyle('title', parent=styles['Title'], fontSize=17, textColor=colors.HexColor('#B34700'))
    sub_style = ParagraphStyle('sub', parent=styles['Normal'], fontSize=9.5, textColor=colors.grey, spaceAfter=10)
    story.append(Paragraph("Physiology Reasoning Q&amp;A - Quick Revision", title_style))
    story.append(Paragraph("Short, examiner-focused answers. <b>Bold text</b> = key line usually awarded marks.", sub_style))
    story.append(Spacer(1, 4))

    for i, (system, qa_list) in enumerate(DATA):
        if i > 0:
            story.append(PageBreak())
        story.append(Paragraph(system, h1))
        for num, (q, a) in enumerate(qa_list, 1):
            story.append(Paragraph(f"Q{num}. {q}", qstyle))
            story.append(Paragraph(f"Ans: {a}", astyle))
    doc.build(story)
    print("done")

if __name__ == "__main__":
    build()