All answers verified against Ganong's Physiology, Guyton & Hall, and Junqueira's Histology.

11. (A) There is net reabsorption of the substance in the tubules. Clearance below the inulin (GFR) value means less of the substance appears in urine than was filtered — the "missing" amount was reabsorbed by the tubules. (If it were secreted, clearance would exceed GFR.)

12. (C) Dyslexia, attention deficit disorder. Word-level decoding difficulty with normal/above-average intelligence, spelling errors and inaccurate reading is classic developmental dyslexia. Per Ganong's Physiology: "Dyslexia is the most common and prevalent of all known learning disabilities. It often coexists with attention deficit disorder" (Ganong's Review of Medical Physiology, 26e).

13. (C) Insulin. Insulin granule translocation and exocytosis from pancreatic β-cells depends on an intact microtubular cytoskeleton. Colchicine (a microtubule inhibitor) blocks insulin secretion by disrupting granule movement to the plasma membrane (Goodman & Gilman's Pharmacological Basis of Therapeutics).

14. (A) LH. Ovulation is triggered by the mid-cycle LH surge (itself driven by the preceding estrogen-induced positive feedback and GnRH pulses). GnRH restores the pulsatile LH release needed for ovulation in hypothalamic (functional hypothalamic) amenorrhea from exercise/undernutrition.

15. (D) Rotating the head to the right. For the right horizontal canal, ampullopetal (utricle-directed) endolymph flow bends stereocilia toward the kinocilium, causing depolarization/excitation. Head rotation to the right produces exactly this flow in the right horizontal canal. (Bending away from the kinocilium or hyperpolarization — options A and C — are inhibitory, not excitatory.)

16. (C) 2.0%. FENa = (UNa × PCr) / (PNa × UCr) × 100 = (33 × 7.5) / (135 × 90) × 100 = 247.5 / 12,150 × 100 ≈ 2.0% (This FENa >1% with these labs actually indicates intrinsic/acute tubular injury pattern — consistent with NSAID-induced acute kidney injury — but the calculated value itself is ~2.0%.)

17. (D) Projection of fibers from neighboring sensory areas into the right-hand area of his left primary somatosensory cortex. The right hand was amputated, so its cortical representation is in the left (contralateral) primary somatosensory cortex. Deafferentation leads adjacent sensory representations (e.g., face) to send collateral projections into the vacated hand territory — the classic cortical remapping basis of phantom limb pain (Kandel's Principles of Neural Science, Fig. 20-14). Answer must specify the left hemisphere, not the right.

18. (B) Vasopressin (ADH). Dehydration raises plasma osmolality, which is sensed by hypothalamic osmoreceptors and stimulates vasopressin release from the posterior pituitary, promoting water reabsorption and reducing urine output. Insulin, aldosterone, and cortisol are not primarily osmolality-driven.

19. (C) Maintenance of the blood-testis barrier. Tight junctions between adjacent Sertoli cells form the blood-testis barrier, protecting developing germ cells from immune attack and maintaining the specialized luminal microenvironment (Junqueira's Basic Histology). FSH is secreted by the pituitary (not into the tubular lumen by Sertoli cells), and testosterone is synthesized by Leydig cells, not Sertoli cells.

20. (B) Flexor withdrawal reflex. The flexor (nociceptive withdrawal) reflex is a polysynaptic spinal reflex; its circuitry also drives the crossed-extensor response, exciting extensor motor neurons in the contralateral limb to maintain postural support while the stimulated limb withdraws (Guyton & Hall, "Crossed Extensor Reflex," accompanying the flexor withdrawal reflex). The stretch reflex and Golgi tendon (inverse myotatic) reflex are monosynaptic/oligosynaptic and ipsilateral; "subliminal occlusion" is not a spinal reflex type.

All confirmed against the library. Here are the answers for Questions 1-10 (Physiology Paper II, Set A):

1. (B) Diabetes insipidus. After adequate saline correction, persistent hypernatremia with polyuria and inappropriately low urine sodium/osmolality indicates the kidney cannot concentrate urine — i.e., an ongoing defect in ADH action or secretion (diabetes insipidus), not simple dehydration. Diabetes mellitus and renal failure don't fit this water-handling defect, and hyperaldosteronism would cause sodium retention with hypokalemia, not this picture.

2. (D) Epinephrine. Epinephrine (a β2-agonist) stimulates Na⁺/K⁺-ATPase, driving potassium into cells and lowering extracellular K⁺ — the same mechanism used clinically (nebulized albuterol) for acute hyperkalemia. Atropine, lactic acid, and glucagon don't produce this intracellular K⁺ shift.

3. (B) Cutting the dorsal roots. Decerebrate rigidity results from unopposed vestibulospinal/reticulospinal facilitation of gamma motor neurons, which sensitizes muscle spindles (the "gamma loop"). Sectioning the dorsal roots removes the spindle afferent input to alpha motor neurons, abolishing the excess extensor tone — a classic finding confirmed in Ganong's Physiology ("cutting dorsal roots to a limb in decerebrate cats immediately eliminated the hyperactivity of extensor muscles").

4. (C) Endolymph volume and pressure. Episodic vertigo with fluctuating hearing loss, aural fullness, and low-pitched tinnitus is classic Meniere's disease, caused by endolymphatic hydrops — increased volume and pressure of endolymph in the membranous labyrinth.

5. (C) Occipital. Per Guyton & Hall's Fixation Movements of the Eyes: the posterior "involuntary" occipital cortical eye fields automatically lock the eyes onto a target (voluntary/involuntary fixation mechanism), distinct from the frontal eye fields, which control voluntary saccadic scanning.

6. (C) Olfactory. The olfactory system has the narrowest range of intensity discrimination among the sensory systems — far smaller than vision or hearing, which can discriminate over enormous intensity ranges.

7. (B) Increased sodium reabsorption by the distal nephron. Liddle syndrome is caused by gain-of-function mutations in the β or γ subunits of the epithelial sodium channel (ENaC) in the distal nephron/collecting duct, causing constitutively increased Na⁺ reabsorption — producing hypertension, volume expansion (suppressing renin/aldosterone), and hypokalemia. It's corrected by ENaC blockers like amiloride, not aldosterone antagonists.

8. (D) A peripheral neuropathy. Combined loss of pain/temperature (spinothalamic), vibration/proprioception (dorsal column), and weakness all within a single limb, with no involvement elsewhere, points to a peripheral nerve/mononeuropathy process rather than a CNS lesion — a CNS (cord or lemniscal) lesion would produce a dissociated pattern (e.g., contralateral pain/temp loss vs. ipsilateral proprioceptive/motor loss), not uniform loss of all modalities in one limb.

9. (A) The mode of administration fails to reproduce the normal pulsatile secretion of the natural hormone. This describes GnRH-like pituitary-axis hormones: continuous (non-pulsatile) exposure causes receptor internalization/desensitization of target cells, whereas pulsatile secretion is required to maintain receptor sensitivity and biological effect — confirmed across Harrison's, Katzung's, and Medical Physiology texts.

10. (C) 20 mL/min. Clearance = (Urine concentration × Urine flow) / Plasma concentration = (100 mg/dL × 2 mL/min) / 10 mg/dL = 200/10 = 20 mL/min (matches the handwritten calculation on the paper).