/* === PHYSL 210 — AUTO-GENERATED gap-fill practice questions === Source: dynamic workflow "physl-gapfill" (audit/wf_gapfill.js). Each question was drafted by a per-module author agent, then ACCEPTED only after BOTH (a) an independent blind solver re-derived the keyed answer and (b) a strict critic confirmed factual correctness, sound explanation, curriculum fit, and non-redundancy. 88 drafted -> 54 kept. Merges into window.QUESTIONS at load (src:"course", gen:true), stem-deduped & idempotent. These are PRACTICE questions only (no exam tag) so the exam/practice partition holds. */ (function(){ if (window.__physlGenLoaded) return; window.__physlGenLoaded = true; const norm = s => (s||"").toLowerCase().replace(/[^a-z0-9]+/g," ").trim(); const GEN = { "cell": [ { "q": "A liver cell is actively synthesising membrane phospholipids and detoxifying a drug. Which organelle carries out BOTH of these functions?", "options": [ "Rough endoplasmic reticulum", "Smooth endoplasmic reticulum", "Golgi apparatus", "Nucleolus" ], "a": 1, "e": "The smooth endoplasmic reticulum synthesises lipids, stores Ca²⁺, and detoxifies drugs (a prominent role in hepatocytes). The rough ER, studded with ribosomes, synthesises proteins and performs their post-translational modifications, while the Golgi sorts and packages proteins and the nucleolus makes ribosomal RNA.", "topicId": "cell-organelles-i-nucleus-er-and", "topic": "Cell Organelles I — Nucleus, ER & Golgi" }, { "q": "The Na⁺/glucose cotransporter moves glucose into a cell against its concentration gradient. What is the IMMEDIATE energy source that powers this uphill movement of glucose?", "options": [ "Direct hydrolysis of ATP by the cotransporter itself", "Simple diffusion of glucose down its own concentration gradient", "Movement of Na⁺ down its electrochemical gradient", "The membrane potential acting directly on uncharged glucose" ], "a": 2, "e": "In secondary active transport, the cotransporter uses the energy stored in the Na⁺ electrochemical gradient — Na⁺ moving down its gradient drives glucose uphill. ATP is not hydrolysed by the cotransporter directly; it is used indirectly by the Na⁺/K⁺ pump to maintain the Na⁺ gradient. Glucose is uncharged, so the membrane potential cannot drive it.", "topicId": "membrane-transport", "topic": "Membrane Transport" } ], "blood": [ { "q": "A patient with chronic gastrointestinal blood loss is found to be iron-deficient. Compared with normal red blood cells, the erythrocytes in this patient's blood smear would most likely appear:", "options": [ "Smaller than normal and pale (microcytic and hypochromic)", "Larger than normal with a normal colour (macrocytic and normochromic)", "Normal in size but darker than normal (normocytic and hyperchromic)", "Sickle-shaped but normal in colour" ], "a": 0, "e": "Iron is required for haem synthesis, so iron deficiency reduces haemoglobin content per cell, producing small (microcytic) and pale (hypochromic) RBCs. Large/macrocytic cells instead characterise B12 or folate deficiency, where impaired DNA synthesis enlarges the cells.", "topicId": "red-blood-cells-haemoglobin-and-anaemia", "topic": "Red Blood Cells, Haemoglobin & Anaemia" }, { "q": "A cell is infected by a virus and secretes interferons. What is the principal protective action of these interferons?", "options": [ "They induce neighbouring cells to make proteins that block viral replication", "They bind directly to free viruses and neutralise them like antibodies", "They form membrane attack complexes that lyse the infected cell", "They present viral antigens to helper T cells on MHC class II molecules" ], "a": 0, "e": "Interferons are chemical mediators released by virus-infected cells that signal nearby cells to synthesise intracellular proteins inhibiting viral replication, an innate (non-specific) defence. Antigen-specific neutralisation is the role of antibodies, while the membrane attack complex is formed by complement.", "topicId": "white-blood-cells-and-innate-immunity", "topic": "White Blood Cells & Innate Immunity" }, { "q": "When a blood vessel is injured and surrounding tissue is damaged, the extrinsic pathway of coagulation is triggered. What is the initiating event of this pathway?", "options": [ "Tissue factor exposed by the damaged tissue activates factor VII", "Factor XII is activated by contact with exposed collagen", "Plasmin cleaves fibrin to expose clotting sites", "Thrombin converts fibrinogen into a stable fibrin mesh" ], "a": 0, "e": "The extrinsic pathway begins when tissue factor (factor III) released from damaged tissue binds and activates factor VII, rapidly launching the cascade toward thrombin. Contact activation of factor XII initiates the separate intrinsic pathway, and fibrin formation by thrombin is the final common step, not the trigger.", "topicId": "platelets-and-haemostasis", "topic": "Platelets & Haemostasis" }, { "q": "An Rh-negative woman carries an Rh-positive fetus. Why is haemolytic disease of the newborn typically a risk in a SUBSEQUENT Rh-positive pregnancy rather than the first?", "options": [ "The first exposure sensitises the mother to make anti-Rh antibodies that cross the placenta in a later pregnancy", "The mother is born with pre-formed anti-Rh antibodies that only reach the fetus after repeated pregnancies", "The first fetus transfers Rh antigen that the mother must accumulate before her plasma can react", "Maternal anti-Rh antibodies are of the IgM class and require several pregnancies to be produced" ], "a": 0, "e": "Anti-Rh antibodies are not naturally pre-formed; the mother is sensitised when fetal Rh-positive cells enter her circulation (usually at the first delivery), after which she produces anti-Rh IgG. These IgG antibodies cross the placenta in a later Rh-positive pregnancy and haemolyse fetal RBCs. (Unlike anti-Rh, the ABO anti-A/anti-B antibodies are the naturally occurring ones.)", "topicId": "coagulation-cascade-and-blood-groups", "topic": "Coagulation Cascade & Blood Groups" } ], "nms": [ { "q": "In the cross-bridge cycle, which event requires the binding of a fresh ATP molecule to the myosin head?", "options": [ "Detachment of the myosin head from actin at the end of the power stroke", "Rotation of the myosin head that produces the power stroke", "Binding of the energized myosin head to exposed actin sites", "Movement of tropomyosin away from the actin binding sites" ], "a": 0, "e": "Binding of a new ATP to myosin lowers myosin's affinity for actin and releases the cross-bridge; subsequent ATP hydrolysis re-energizes the head. This is why rigor mortis occurs when ATP is depleted after death — without ATP, cross-bridges cannot detach. The power stroke (option B) is driven by release of Pi/ADP, not by ATP binding.", "topicId": "cross-bridge-cycling-and-muscle-fibre", "topic": "Cross-bridge Cycling & Muscle Fibre Types" }, { "q": "During excitation–contraction coupling, why can a skeletal muscle fiber contract even when bathed in a Ca²⁺-free extracellular solution?", "options": [ "The Ca²⁺ for contraction is released from the sarcoplasmic reticulum, not drawn from outside the cell", "The T-tubule action potential directly admits extracellular Ca²⁺ through DHP receptors", "Troponin can expose actin binding sites without any rise in cytosolic Ca²⁺", "ACh release at the neuromuscular junction supplies the Ca²⁺ needed by troponin" ], "a": 0, "e": "In skeletal muscle the depolarized DHP receptor is mechanically linked to the ryanodine receptor and opens it to release Ca²⁺ stored in the sarcoplasmic reticulum, so contraction does not depend on extracellular Ca²⁺ entry. This differs from cardiac muscle, where a small influx of extracellular Ca²⁺ is required to trigger SR Ca²⁺ release (option B describes the cardiac, not skeletal, mechanism).", "topicId": "muscle-the-nmj-and-excitation-contraction", "topic": "Muscle, the NMJ & Excitation–Contraction Coupling" } ], "cns": [ { "q": "In an ascending sensory pathway, second-order neurons carrying pain and temperature information cross the midline at what level?", "options": [ "In the spinal cord, near the level at which the information enters", "In the medulla oblongata, at the level of the gracile and cuneate nuclei", "In the midbrain, just before the thalamus", "They do not cross; the pathway is entirely ipsilateral" ], "a": 0, "e": "In the anterolateral (spinothalamic) pathway for pain and temperature, second-order neurons cross the midline within the spinal cord at or near the segment of entry. This contrasts with the dorsal column pathway, whose axons ascend ipsilaterally and only decussate in the medulla.", "topicId": "spinal-tracts", "topic": "Spinal tracts" }, { "q": "Which feature is characteristic of REM (rapid eye movement) sleep but not of slow-wave (NREM) sleep?", "options": [ "Large, slow, synchronized EEG waves", "A near-complete loss of skeletal muscle tone (atonia)", "A progressive fall in heart rate and blood pressure to their lowest levels", "An EEG dominated by high-amplitude delta waves" ], "a": 1, "e": "REM sleep features active suppression of skeletal muscle tone (atonia) alongside a low-amplitude, high-frequency EEG resembling the awake state. Large, slow, synchronized delta waves and the lowest heart rate and blood pressure are hallmarks of slow-wave (NREM) sleep, not REM.", "topicId": "sleep-and-consciousness", "topic": "Sleep & consciousness" } ], "ans": [ { "q": "Compared with the sympathetic division, the parasympathetic division characteristically has:", "options": [ "Long preganglionic fibres and short postganglionic fibres", "Short preganglionic fibres and long postganglionic fibres", "Long preganglionic and long postganglionic fibres", "No synapse between the CNS and the effector organ" ], "a": 0, "e": "Parasympathetic ganglia sit on or near the effector organ, so preganglionic fibres are long and postganglionic fibres are short. The sympathetic pattern is the reverse (short pre, long post) because its ganglia lie close to the spinal cord.", "topicId": "sympathetic-and-parasympathetic-anatomy", "topic": "Sympathetic & parasympathetic anatomy" }, { "q": "Most of the parasympathetic innervation to the thoracic and abdominal viscera (heart, lungs, stomach, and small intestine) is carried by the:", "options": [ "Greater splanchnic nerve", "Vagus nerve (cranial nerve X)", "Sympathetic trunk", "Phrenic nerve" ], "a": 1, "e": "The vagus (CN X) supplies parasympathetic fibres to nearly all thoracic and abdominal organs, accounting for roughly three-quarters of all parasympathetic outflow. The splanchnic nerves and sympathetic trunk are sympathetic, not parasympathetic, pathways.", "topicId": "sympathetic-and-parasympathetic-anatomy", "topic": "Sympathetic & parasympathetic anatomy" }, { "q": "During sympathetic activation the pupil dilates, whereas during parasympathetic activation it constricts. This occurs because:", "options": [ "Sympathetic fibres contract the radial muscle of the iris and parasympathetic fibres contract the circular (sphincter) muscle", "Both divisions act on the same muscle but release different neurotransmitters", "Sympathetic fibres relax the lens while parasympathetic fibres contract it", "Only the sympathetic division innervates the iris; dilation is passive" ], "a": 0, "e": "The iris has two antagonistic muscles: the radial (dilator) muscle is contracted by sympathetic fibres to widen the pupil, and the circular (sphincter) muscle is contracted by parasympathetic fibres to narrow it. The pupillary response is therefore an example of dual innervation acting on different muscles, not on the same one.", "topicId": "neurotransmitters-and-organ-effects", "topic": "Neurotransmitters & organ effects" } ], "ss": [ { "q": "When light strikes a photoreceptor, activated opsin stimulates the G-protein transducin, which in turn activates an enzyme that lowers cytoplasmic cyclic GMP. Which enzyme is activated to produce this fall in cGMP?", "options": [ "Guanylyl cyclase", "cGMP-phosphodiesterase", "Adenylyl cyclase", "Na⁺/K⁺-ATPase" ], "a": 1, "e": "Transducin activates cGMP-phosphodiesterase, which rapidly degrades cGMP; the resulting fall in cGMP closes the cation channels and hyperpolarises the cell. Guanylyl cyclase does the opposite — it synthesises cGMP in the dark to keep those channels open.", "topicId": "vision-and-phototransduction", "topic": "Vision & phototransduction" }, { "q": "How does the central nervous system distinguish the type (modality) of a stimulus — for example, light versus sound versus touch?", "options": [ "By which specific receptors and dedicated neural pathways are activated", "By the frequency of action potentials arriving from the receptor", "By the amplitude of the receptor potential generated", "By how rapidly the activated receptor adapts" ], "a": 0, "e": "Modality is coded by the labeled-line principle: each receptor type is most sensitive to one form of energy and projects through a dedicated pathway to a specific brain region, so the modality is set by which line is active. Action-potential frequency encodes stimulus intensity, not which modality is being sensed.", "topicId": "overview", "topic": "Senses — Overview / cross-cutting" } ], "cardio": [ { "q": "In the heart, the rapid upstroke (phase 0) of a fast-type action potential in a ventricular muscle cell and that of a slow-type action potential in an SA-node cell are produced, respectively, by:", "options": [ "Na⁺ influx through fast voltage-gated Na⁺ channels; Ca²⁺ influx through L-type Ca²⁺ channels", "Ca²⁺ influx through L-type Ca²⁺ channels; Na⁺ influx through fast voltage-gated Na⁺ channels", "Na⁺ influx through fast voltage-gated Na⁺ channels; K⁺ efflux through voltage-gated K⁺ channels", "Ca²⁺ influx through T-type Ca²⁺ channels; Na⁺ influx through fast voltage-gated Na⁺ channels" ], "a": 0, "e": "In fast-response (working myocardial and Purkinje) cells the phase-0 upstroke is a rapid Na⁺ influx through fast voltage-gated Na⁺ channels, whereas SA-node (slow-response) cells lack functional fast Na⁺ channels, so their slower upstroke depends on Ca²⁺ influx through L-type Ca²⁺ channels. The reversed pairing (option B) describes the cell types backwards.", "topicId": "cardiac-action-potentials", "topic": "Cardiac action potentials" } ], "gi": [ { "q": "Compared with most other GI secretions, salivary secretion is unusual because it is:", "options": [ "Stimulated by parasympathetic activity but inhibited by sympathetic activity", "Stimulated by both parasympathetic and sympathetic activity", "Controlled almost entirely by circulating gastrin", "Independent of autonomic input and driven only by local reflexes" ], "a": 1, "e": "Salivary glands are unusual in that BOTH autonomic divisions stimulate secretion: parasympathetic input produces copious watery saliva, while sympathetic input produces a smaller volume of thicker, enzyme-rich saliva. For most GI functions the sympathetic system is inhibitory.", "topicId": "mouth-saliva-and-swallowing", "topic": "Mouth, saliva & swallowing" }, { "q": "During the pharyngeal phase of swallowing, aspiration of food into the trachea is prevented mainly by:", "options": [ "Closure of the upper oesophageal sphincter", "Elevation of the larynx and folding of the epiglottis over the glottis", "Voluntary contraction of the tongue against the hard palate", "Relaxation of the lower oesophageal sphincter" ], "a": 1, "e": "In the involuntary pharyngeal phase, the larynx is pulled up and forward so the epiglottis folds back over the closed glottis, sealing the airway while the bolus passes into the oesophagus. The lower oesophageal sphincter relaxing occurs later and does not protect the airway.", "topicId": "mouth-saliva-and-swallowing", "topic": "Mouth, saliva & swallowing" }, { "q": "The 'alkaline tide' (a transient rise in venous blood pH after a meal) results from gastric parietal cells:", "options": [ "Exporting bicarbonate into the blood as they secrete H⁺ into the lumen", "Absorbing hydrogen ions from the gastric lumen into the blood", "Secreting bicarbonate directly into the gastric lumen", "Releasing gastrin into the portal circulation" ], "a": 0, "e": "Parietal cells generate H⁺ and HCO3⁻ from CO2 and water; H⁺ is pumped into the lumen while HCO3⁻ is exchanged for Cl⁻ into the blood, transiently raising venous pH (the alkaline tide). Bicarbonate is exported to blood, not secreted into the lumen by parietal cells.", "topicId": "stomach-and-gastric-secretion", "topic": "Stomach & gastric secretion" }, { "q": "Pancreatic trypsinogen is converted to active trypsin in the small intestine by:", "options": [ "Hydrochloric acid carried over from the stomach", "Enterokinase (enteropeptidase) on the duodenal brush border", "Secretin released from duodenal S cells", "Bile salts within micelles" ], "a": 1, "e": "Enterokinase (enteropeptidase), a brush-border enzyme of the duodenal enterocytes, cleaves trypsinogen to trypsin; trypsin then activates the other pancreatic zymogens. This protects the pancreas, since the enzymes are activated only after reaching the intestine.", "topicId": "pancreas-liver-and-bile", "topic": "Pancreas, liver & bile" }, { "q": "Most bile salts entering the small intestine are:", "options": [ "Excreted unchanged in the faeces", "Reabsorbed in the terminal ileum and returned to the liver via the portal vein", "Broken down into bilirubin in the colon", "Converted to cholesterol by intestinal bacteria" ], "a": 1, "e": "In the enterohepatic circulation, roughly 95% of bile salts are actively reabsorbed in the terminal ileum and carried back to the liver in portal blood for re-secretion, so only a small fraction is lost in faeces. Bilirubin, not bile salts, is the pigment derived from heme breakdown.", "topicId": "pancreas-liver-and-bile", "topic": "Pancreas, liver & bile" }, { "q": "Glucose is absorbed across the APICAL membrane of small-intestinal enterocytes by:", "options": [ "Secondary active transport coupled to sodium (SGLT1)", "Simple diffusion through the lipid bilayer", "Facilitated diffusion via GLUT5", "Primary active transport using ATP directly" ], "a": 0, "e": "Glucose (and galactose) enters the enterocyte against its gradient via the apical SGLT1 cotransporter, powered by the inward Na⁺ gradient maintained by the basolateral Na⁺/K⁺-ATPase. GLUT5 carries fructose, and glucose exits the basolateral side by facilitated diffusion through GLUT2.", "topicId": "small-intestine-digestion-and-absorption", "topic": "Small-intestine digestion & absorption" }, { "q": "Mass movements that propel colonic contents toward the rectum are often triggered after a meal by the:", "options": [ "Gastrocolic reflex", "Migrating motor complex", "Enterogastric reflex", "Defecation reflex" ], "a": 0, "e": "The gastrocolic reflex links distension of the stomach (and duodenum) to increased colonic motility, producing the strong mass movements that often follow eating. The enterogastric reflex instead slows gastric emptying.", "topicId": "large-intestine-and-water-balance", "topic": "Large intestine & water balance" } ], "resp": [ { "q": "A patient breathes through a long snorkel that adds 250 mL to the volume of the conducting airways. Compared with breathing without the snorkel at the same tidal volume and frequency, what is the direct effect on gas exchange?", "options": [ "Alveolar ventilation falls because a larger fraction of each breath stays in dead space", "Alveolar ventilation rises because total dead space is now better ventilated", "Gas exchange is unaffected because the snorkel adds to the respiratory zone", "Pulmonary diffusing capacity falls because the alveolar membrane thickens" ], "a": 0, "e": "The snorkel enlarges the conducting (dead-space) volume, so more of each fixed tidal volume merely fills airways that do not exchange gas; alveolar ventilation (VA = (VT − VD) × f) therefore falls. The membrane thickness is unchanged, so diffusing capacity per se is not the issue.", "topicId": "functional-anatomy-and-zones", "topic": "Functional anatomy & zones" }, { "q": "If a stab wound opens the pleural cavity to the atmosphere on one side, what happens to that lung and why?", "options": [ "The lung collapses because intrapleural pressure rises to atmospheric, abolishing the transpulmonary pressure", "The lung over-inflates because atmospheric air is pushed directly into the alveoli", "The lung is unaffected because the diaphragm still generates negative alveolar pressure", "The lung collapses because surfactant is washed out by the entering air" ], "a": 0, "e": "The lung is held expanded by a positive transpulmonary pressure (Palv − Pip), which exists only because Pip is normally subatmospheric. Equalising Pip with atmospheric pressure makes transpulmonary pressure zero, so elastic recoil collapses the lung. Surfactant loss is not the mechanism.", "topicId": "mechanics-and-pressures", "topic": "Mechanics & pressures" }, { "q": "At the very start of a quiet inspiration, before any air has entered the lungs, which statement about alveolar pressure (Palv) is correct?", "options": [ "Palv becomes slightly negative (subatmospheric) because thoracic expansion increases alveolar volume", "Palv becomes slightly positive because the diaphragm compresses the alveoli", "Palv equals atmospheric pressure throughout inspiration", "Palv equals intrapleural pressure once the glottis opens" ], "a": 0, "e": "Diaphragm and external intercostal contraction expand the thorax and alveoli; by Boyle's law the increased alveolar volume drops Palv below atmospheric, creating the gradient that draws air in. Palv only equals atmospheric again at end-inspiration when flow stops.", "topicId": "mechanics-and-pressures", "topic": "Mechanics & pressures" }, { "q": "By the law of Laplace (P = 2T/r), why would small alveoli tend to empty into larger ones if surface tension (T) were the same in both?", "options": [ "Smaller alveoli generate a higher collapsing pressure for a given surface tension", "Larger alveoli generate a higher collapsing pressure because they hold more air", "Pressure is independent of radius, so the alveoli stay equal", "Smaller alveoli have lower surface tension and therefore higher pressure" ], "a": 0, "e": "For a constant T, pressure is inversely proportional to radius, so a small alveolus has a higher inward pressure and would empty into a larger one. Surfactant prevents this by lowering T more in smaller alveoli, equalising pressures and stabilising the lung.", "topicId": "surfactant-and-compliance", "topic": "Surfactant & compliance" }, { "q": "A patient with pulmonary fibrosis has stiff, scarred lungs. How is lung compliance changed and what is the consequence for breathing?", "options": [ "Compliance is decreased, so more work is required to inflate the lungs", "Compliance is increased, so the lungs inflate too easily and trap air", "Compliance is decreased, so the lungs recoil too weakly on expiration", "Compliance is unchanged because fibrosis affects only the airways" ], "a": 0, "e": "Fibrosis stiffens lung tissue, lowering compliance (ΔV/ΔP), so a larger pressure change is needed for a given volume change and the work of inspiration rises. Increased compliance with air trapping is the picture of emphysema, the opposite condition.", "topicId": "surfactant-and-compliance", "topic": "Surfactant & compliance" }, { "q": "Spirometry shows a markedly reduced FEV1/FVC ratio. Which pattern does this most strongly indicate?", "options": [ "An obstructive disorder, because expiratory airflow is disproportionately limited", "A restrictive disorder, because total lung volume is reduced", "Normal lungs, because the ratio is unaffected by disease", "A restrictive disorder, because the airways are widened" ], "a": 0, "e": "In obstruction (e.g. asthma, COPD) airflow is limited, so the volume exhaled in the first second falls more than FVC, lowering the FEV1/FVC ratio. In restriction both FEV1 and FVC shrink roughly together, so the ratio is preserved or even high.", "topicId": "lung-volumes-and-spirometry", "topic": "Lung volumes & spirometry" }, { "q": "According to Henry's law, why does breathing 100% O₂ at one atmosphere add relatively little oxygen to the plasma compared with the amount carried by haemoglobin?", "options": [ "Oxygen has a low solubility, so even a high partial pressure dissolves only a small amount in plasma", "Oxygen has a high solubility, but plasma volume is too small to matter", "Henry's law applies only to CO₂, not to O₂", "Dissolved oxygen is proportional to temperature, not partial pressure" ], "a": 0, "e": "Henry's law states the amount of gas dissolved equals partial pressure × solubility. Because O₂ is poorly soluble in plasma, raising its partial pressure adds little dissolved O₂; the vast majority of oxygen is instead carried bound to haemoglobin.", "topicId": "gas-exchange-and-v-q", "topic": "Gas exchange & V/Q" }, { "q": "As blood passes through systemic capillaries and haemoglobin gives up oxygen, its ability to carry carbon dioxide increases. This relationship is best described as the:", "options": [ "Haldane effect, in which deoxygenation of haemoglobin enhances CO₂ carriage", "Bohr effect, in which deoxygenation of haemoglobin enhances CO₂ carriage", "Chloride shift, in which oxygenation of haemoglobin enhances CO₂ carriage", "Bicarbonate buffering, in which haemoglobin releases H⁺ to carry more O₂" ], "a": 0, "e": "The Haldane effect describes how deoxygenated haemoglobin binds H⁺ and forms carbamino compounds more readily, increasing CO₂ uptake in the tissues. The Bohr effect is the complementary phenomenon describing how CO₂/H⁺ promote O₂ unloading.", "topicId": "o-and-co-transport", "topic": "O₂ & CO₂ transport" } ], "renal": [ { "q": "Which renal blood vessels run alongside the long loops of Henle and are essential for preserving the medullary osmotic gradient?", "options": [ "The peritubular capillaries", "The vasa recta", "The afferent arterioles", "The interlobular arteries" ], "a": 1, "e": "The vasa recta are the hairpin capillaries that descend into the medulla beside the long loops of Henle of juxtamedullary nephrons; by acting as countercurrent exchangers they remove reabsorbed water and solute without washing out the gradient. Peritubular capillaries surround the cortical tubules and do not dip into the medulla.", "topicId": "the-nephron", "topic": "The nephron" }, { "q": "Given a glomerular capillary hydrostatic pressure of 60 mmHg, a Bowman's-space hydrostatic pressure of 15 mmHg, and a glomerular-capillary plasma colloid osmotic pressure of 30 mmHg (fluid in Bowman's space being protein-free), what is the net filtration pressure?", "options": [ "75 mmHg, favouring filtration", "45 mmHg, favouring filtration", "15 mmHg, favouring filtration", "15 mmHg, favouring reabsorption" ], "a": 2, "e": "Net filtration pressure = P(GC) − P(BS) − π(GC) = 60 − 15 − 30 = +15 mmHg favouring filtration. The colloid osmotic pressure opposes filtration and must be subtracted, so the answer is not 45; because protein is essentially absent from the filtrate, there is no Bowman's-space oncotic term to add.", "topicId": "glomerular-filtration", "topic": "Glomerular filtration" }, { "q": "The filtration fraction is best defined as the ratio of:", "options": [ "Glomerular filtration rate to renal plasma flow", "Renal plasma flow to renal blood flow", "Glomerular filtration rate to urine flow rate", "Filtered solute load to excreted solute load" ], "a": 0, "e": "Filtration fraction = GFR / renal plasma flow, normally about 0.20, meaning roughly one-fifth of the plasma entering the glomeruli is filtered into Bowman's space. The ratio of plasma flow to blood flow simply reflects the haematocrit and is not the filtration fraction.", "topicId": "glomerular-filtration", "topic": "Glomerular filtration" }, { "q": "Compared with the glomerular capillaries, the peritubular capillaries strongly favour bulk reabsorption of fluid because they have a:", "options": [ "Low hydrostatic pressure and a high plasma colloid osmotic pressure", "High hydrostatic pressure and a low plasma colloid osmotic pressure", "High hydrostatic pressure and a high plasma colloid osmotic pressure", "Low hydrostatic pressure and a low plasma colloid osmotic pressure" ], "a": 0, "e": "After filtration, the blood entering the peritubular capillaries has lost protein-free fluid, so its colloid osmotic pressure is high, while its hydrostatic pressure is low (downstream of the efferent arteriole). Both forces therefore drive reabsorbed fluid from the interstitium into the capillary, the opposite of the high-hydrostatic, filtration-favouring glomerular capillaries.", "topicId": "tubular-reabsorption-and-secretion", "topic": "Tubular reabsorption & secretion" }, { "q": "A reabsorbed solute shows a transport maximum (Tm). This means that once the plasma concentration is high enough, the rate of reabsorption:", "options": [ "Continues to rise in direct proportion to plasma concentration", "Plateaus because the membrane transporters are saturated", "Falls to zero because the transporters are inhibited", "Is limited only by the glomerular filtration rate" ], "a": 1, "e": "A transport maximum reflects saturation of a finite number of carrier proteins; beyond the Tm, additional filtered solute cannot be reabsorbed and is excreted, so reabsorption plateaus. It does not continue rising in proportion to plasma concentration, which is the hallmark of a non-saturable (e.g., diffusion-limited) process.", "topicId": "tubular-reabsorption-and-secretion", "topic": "Tubular reabsorption & secretion" }, { "q": "A well-hydrated person drinks a large volume of water. As plasma osmolarity falls, the expected renal response is:", "options": [ "Increased ADH secretion and a small volume of concentrated urine", "Decreased ADH secretion and a large volume of dilute urine", "Increased aldosterone secretion and increased Na⁺ retention", "Decreased glomerular filtration rate and decreased urine flow" ], "a": 1, "e": "A fall in plasma osmolarity is sensed by hypothalamic osmoreceptors and suppresses ADH release; with little ADH, the collecting ducts remain water-impermeable, so the dilute fluid leaving the ascending limb is excreted as a large volume of hypo-osmotic urine. Aldosterone responds to Na⁺/volume and angiotensin II, not to a pure water load.", "topicId": "salt-and-water-balance", "topic": "Salt & water balance" }, { "q": "Following a significant haemorrhage, ADH secretion increases even though plasma osmolarity may be normal. The receptors primarily responsible for this increase are the:", "options": [ "Hypothalamic osmoreceptors", "Cardiovascular baroreceptors", "Renal macula densa cells", "Carotid-body chemoreceptors" ], "a": 1, "e": "A large fall in blood volume or pressure reduces firing of arterial and cardiopulmonary baroreceptors, which reflexively stimulates ADH release to promote water retention. Osmoreceptors drive ADH in response to osmolarity changes, not to the volume loss of haemorrhage; chemoreceptors sense blood gases.", "topicId": "salt-and-water-balance", "topic": "Salt & water balance" }, { "q": "Which property of the thick ascending limb of the loop of Henle is essential for establishing the medullary osmotic gradient?", "options": [ "It is highly permeable to water but does not transport NaCl", "It actively reabsorbs NaCl but is impermeable to water", "It reabsorbs water and NaCl in equal proportions", "It secretes NaCl into the lumen while reabsorbing water" ], "a": 1, "e": "The thick ascending limb actively pumps NaCl out of the lumen yet is impermeable to water, so it dilutes the tubular fluid while depositing solute in the medullary interstitium — the single effect that the countercurrent multiplier magnifies. If it were water-permeable, water would follow the salt and no gradient could form.", "topicId": "medullary-gradient-and-concentration", "topic": "Medullary gradient & concentration" }, { "q": "In addition to NaCl, which solute contributes substantially to the high osmolarity of the inner medullary interstitium during antidiuresis?", "options": [ "Glucose", "Urea", "Bicarbonate", "Albumin" ], "a": 1, "e": "Under high ADH, the inner medullary collecting duct becomes permeable to urea, allowing urea to accumulate in the interstitium where it adds roughly half of the medullary osmolarity that concentrates the urine. Glucose and bicarbonate are reabsorbed earlier and do not accumulate in the medulla; albumin is not filtered in appreciable amounts.", "topicId": "medullary-gradient-and-concentration", "topic": "Medullary gradient & concentration" }, { "q": "When the kidney must add NEW bicarbonate to the blood to correct an acid load, it does so primarily by:", "options": [ "Filtering additional bicarbonate at the glomerulus", "Excreting H⁺ buffered as titratable acid and ammonium in the urine", "Reabsorbing the bicarbonate that was filtered at the glomerulus", "Increasing the secretion of potassium into the tubular lumen" ], "a": 1, "e": "Reabsorbing filtered bicarbonate only conserves existing bicarbonate; to generate new bicarbonate the tubule must secrete H⁺ that is excreted bound to urinary buffers — phosphate (titratable acid) and ammonia (as ammonium) — with one new HCO₃⁻ returned to the blood for each H⁺ excreted in this form. Simply reabsorbing filtered HCO₃⁻ adds no new base.", "topicId": "k-and-acid-base-balance", "topic": "K⁺ & acid–base balance" }, { "q": "In uncontrolled diabetes mellitus, plasma glucose exceeds the renal threshold and unreabsorbed glucose remains in the tubule. The resulting large urine volume is best explained by:", "options": [ "Glucose stimulating ADH secretion from the collecting duct", "Unreabsorbed glucose osmotically retaining water in the tubular lumen", "Increased aldosterone causing excess Na⁺ and water excretion", "A direct increase in glomerular filtration rate caused by glucose" ], "a": 1, "e": "Once the glucose transporters are saturated, the glucose remaining in the lumen is an effective osmole that holds water in the tubule and reduces water reabsorption, producing an osmotic diuresis with polyuria. ADH and aldosterone are not stimulated by luminal glucose, and the polyuria is a tubular osmotic effect rather than a rise in GFR.", "topicId": "glucose-handling-and-diabetes", "topic": "Glucose handling & diabetes" } ], "endo": [ { "q": "A water-soluble peptide hormone binds a receptor on the surface of its target cell. The most common way this binding alters cell activity is by:", "options": [ "Diffusing into the nucleus to directly bind hormone-response elements on DNA", "Activating a membrane receptor that generates intracellular second messengers such as cAMP", "Being transported into the cytoplasm to bind a steroid-type receptor", "Entering the mitochondria to increase ATP synthesis directly" ], "a": 1, "e": "Peptide hormones are lipid-insoluble and cannot cross the plasma membrane, so they bind surface receptors that trigger second-messenger cascades (e.g., cAMP) or open ion channels. Direct binding to nuclear DNA-response elements is the mechanism of lipid-soluble steroid and thyroid hormones, not peptides.", "topicId": "hormone-classes-and-action", "topic": "Hormone classes & action" }, { "q": "When a target tissue is chronically exposed to a high concentration of a hormone, its responsiveness often decreases over time. This is most directly explained by:", "options": [ "An increase in the number of receptors (up-regulation)", "A decrease in the number of receptors (down-regulation)", "Conversion of the hormone into a more potent metabolite", "Increased plasma binding-protein concentration" ], "a": 1, "e": "Persistently elevated hormone levels typically cause down-regulation — a reduction in the number of target-cell receptors — which lowers the cell's responsiveness. Up-regulation is the opposite response, usually seen when hormone levels are chronically low.", "topicId": "hormone-classes-and-action", "topic": "Hormone classes & action" }, { "q": "Thyroid-stimulating hormone (TSH), ACTH, and the gonadotropins (FSH/LH) are all examples of tropic hormones because they:", "options": [ "Are stored in and released from the posterior pituitary", "Act mainly on other endocrine glands to control their secretion", "Are lipid-soluble and act through intracellular receptors", "Are secreted directly by the hypothalamus into the systemic blood" ], "a": 1, "e": "A tropic hormone is one whose major target is another endocrine gland, whose hormone output it controls (e.g., TSH stimulates the thyroid). These are all anterior-pituitary peptide hormones acting through surface receptors, not posterior-pituitary or lipid-soluble hormones.", "topicId": "hypothalamus-and-pituitary", "topic": "Hypothalamus & pituitary" }, { "q": "Adequate dietary intake of which element is ESSENTIAL for the synthesis of thyroid hormones (T3 and T4)?", "options": [ "Iron", "Calcium", "Iodine", "Magnesium" ], "a": 2, "e": "T3 and T4 are made by iodinating tyrosine residues on thyroglobulin, so iodine is an indispensable raw material; severe dietary iodine deficiency impairs hormone synthesis and can cause goitre. Iron, calcium, and magnesium are not incorporated into the thyroid hormone molecule.", "topicId": "thyroid-gland", "topic": "Thyroid gland" }, { "q": "During acute stress, the adrenal MEDULLA contributes to the response primarily by secreting:", "options": [ "Cortisol and aldosterone into the blood", "Epinephrine (and some norepinephrine) into the blood", "Antidiuretic hormone and oxytocin", "Thyroid hormone and parathyroid hormone" ], "a": 1, "e": "The adrenal medulla behaves like a modified sympathetic ganglion: on sympathetic stimulation its chromaffin cells release epinephrine (mainly) and norepinephrine into the circulation. Cortisol and aldosterone are products of the adrenal cortex, not the medulla.", "topicId": "adrenal-gland-and-stress", "topic": "Adrenal gland & stress" }, { "q": "Several hours after a meal, plasma glucose begins to fall. The pancreatic hormone secreted in response, and its main action, is:", "options": [ "Insulin, which stimulates hepatic glycogen breakdown", "Glucagon, which stimulates hepatic glycogenolysis and gluconeogenesis", "Insulin, which stimulates gluconeogenesis in the liver", "Glucagon, which stimulates glucose uptake into muscle and fat" ], "a": 1, "e": "Falling glucose stimulates pancreatic alpha cells to release glucagon, which acts mainly on the liver to break down glycogen and make new glucose, restoring blood glucose. Insulin secretion falls (not rises) in this state, and glucagon does not promote tissue glucose uptake — that is an insulin action.", "topicId": "pancreas-and-glucose", "topic": "Pancreas & glucose" }, { "q": "A patient has low plasma thyroid hormone together with a HIGH plasma TSH. This pattern is most consistent with:", "options": [ "A primary defect in the thyroid gland itself", "A defect in the anterior pituitary's secretion of TSH", "Excess negative feedback from high cortisol", "Overproduction of thyroid hormone by a tumour" ], "a": 0, "e": "If the thyroid gland itself fails (primary hypothyroidism), thyroid hormone is low and the resulting loss of negative feedback drives TSH high. A pituitary (secondary) defect would produce low thyroid hormone with low or inappropriately normal TSH, not elevated TSH.", "topicId": "endocrine-disorders", "topic": "Endocrine disorders" }, { "q": "Type 1 diabetes mellitus is best characterised as a disorder resulting from:", "options": [ "Excessive secretion of insulin by pancreatic beta cells", "Destruction of pancreatic beta cells leading to insulin deficiency", "Reduced target-tissue responsiveness despite high insulin levels", "Overproduction of glucagon by an adrenal tumour" ], "a": 1, "e": "Type 1 diabetes arises from destruction of the insulin-secreting beta cells of the pancreas, producing an absolute lack of insulin and hyperglycaemia. Reduced tissue responsiveness with adequate or high insulin describes type 2 diabetes, a different mechanism.", "topicId": "endocrine-disorders", "topic": "Endocrine disorders" } ], "repro": [ { "q": "The blood-testis barrier, which isolates developing germ cells in the adluminal compartment from blood-borne substances and the immune system, is formed by:", "options": [ "Tight junctions between adjacent Sertoli cells", "Gap junctions between Leydig cells", "The basement membrane surrounding the seminiferous tubule", "Tight junctions between adjacent spermatogonia" ], "a": 0, "e": "Tight junctions joining neighbouring Sertoli cells create the blood-testis barrier, protecting meiotic and post-meiotic germ cells (which express novel antigens) from immune attack. The basement membrane and Leydig cells do not form this barrier, and spermatogonia lie outside it in the basal compartment.", "topicId": "male-reproduction-and-spermatogenesis", "topic": "Male reproduction & spermatogenesis" }, { "q": "During the secretory phase of the uterine cycle, the endometrium develops coiled glands rich in glycogen secretions in preparation for implantation. This change is driven primarily by:", "options": [ "Progesterone secreted by the corpus luteum", "Estrogen secreted by the developing antral follicles", "The mid-cycle surge of luteinizing hormone", "Follicle-stimulating hormone from the anterior pituitary" ], "a": 0, "e": "After ovulation, progesterone from the corpus luteum converts the estrogen-primed proliferative endometrium into a secretory one, with tortuous glands secreting glycogen to support a possible embryo. Estrogen drives the earlier proliferative (growth) phase, not the secretory transformation.", "topicId": "female-cycle-and-menstruation", "topic": "Female cycle & menstruation" }, { "q": "In a non-fertile cycle, the corpus luteum regresses about 10–14 days after ovulation. The immediate hormonal cause of this regression is:", "options": [ "Withdrawal of luteinizing hormone support in the absence of hCG", "A second surge of follicle-stimulating hormone", "Rising inhibin secreted by granulosa cells", "A sharp rise in human chorionic gonadotropin" ], "a": 0, "e": "The corpus luteum depends on continued LH support; when no pregnancy occurs there is no hCG to take over, and the corpus luteum degenerates as LH levels fall, causing progesterone and estrogen to drop. hCG would instead rescue the corpus luteum, and FSH/inhibin do not sustain it.", "topicId": "control-of-ovarian-function", "topic": "Control of ovarian function" }, { "q": "In a breastfeeding mother, the suckling stimulus sustains high secretion of a hormone that both maintains milk production and suppresses the ovarian cycle (lactational amenorrhea). This hormone is:", "options": [ "Prolactin", "Oxytocin", "Estrogen", "Human chorionic gonadotropin" ], "a": 0, "e": "Suckling maintains elevated prolactin, which drives continued milk synthesis and also inhibits hypothalamic GnRH, suppressing FSH/LH and thereby ovulation (lactational amenorrhea). Oxytocin causes only milk ejection, not milk synthesis or cycle suppression.", "topicId": "parturition-and-lactation", "topic": "Parturition & lactation" } ] }; const QB = window.QUESTIONS || (window.QUESTIONS = {}); let added = 0; for (const m of Object.keys(GEN)) { QB[m] = QB[m] || []; const seen = new Set(QB[m].map(q => norm(q.q))); for (const q of GEN[m]) { const k = norm(q.q); if (!k || seen.has(k)) continue; seen.add(k); QB[m].push({ q:q.q, options:q.options, a:q.a, e:q.e, src:"course", gen:true, topic:q.topic, topicId:q.topicId }); added++; } } window.__physlGenCount = added; })();