Aim to answer every question before checking. Missed questions point you to the sections you need most.
1. (10.1) Homeostasis is best defined as:
D. Homeostasis holds physiologic variables (temperature, pH, glucose, osmolarity) near a setpoint despite external changes, usually via negative-feedback loops.
2. (10.1) Which example best illustrates negative feedback?
A. Negative feedback opposes change to return the system to setpoint. B and C are classic positive-feedback loops.
3. (10.2) The functional unit of the kidney is the:
C. Each kidney has about a million nephrons, the minimal unit that filters, reabsorbs, and secretes to form urine.
4. (10.2) Blood enters the glomerulus via the:
B. Afferent → glomerulus → efferent. The glomerulus is unique in sitting between two arterioles rather than an arteriole and a venule, which sustains high filtration pressure.
5. (10.3) Glomerular filtration is driven primarily by:
D. Net filtration =
Pgc minus (
Pbc + π_gc). Arteriolar tone (afferent and efferent) tunes
Pgc and therefore GFR.
6. (10.3) Normal glomerular filtrate differs from plasma because it:
A. The filtration barrier (fenestrae, basement membrane, podocyte slit diaphragm) keeps large proteins and cells in the blood. Proteinuria signals damage to this barrier.
7. (10.4) Most glucose, amino acids, and bicarbonate are reabsorbed in the:
C. The PCT has extensive microvilli and reclaims essentially all filtered glucose (via SGLT2), amino acids, and about 85% of bicarbonate.
8. (10.4) Water reabsorption in the proximal convoluted tubule:
B. The PCT is always permeable to water via AQP1. Solute reabsorption sets up the gradient and water follows.
9. (10.5) The countercurrent multiplier system in the loop of Henle establishes:
A. The interstitial gradient rises from about 300 mOsm at the cortex to about 1200 mOsm deep in the medulla, allowing water to leave the collecting duct when ADH is present.
10. (10.5) The descending limb of the loop of Henle is permeable to:
D. The thin descending limb concentrates tubular fluid by letting water exit into the hypertonic medulla. The ascending limb is the mirror image: solute out, water stays.
11. (10.6) ADH (vasopressin) acts on the collecting duct to:
B. ADH binds V2 receptors and triggers AQP2 insertion on the luminal side of principal cells. Water flows out of the duct into the hypertonic interstitium, concentrating urine.
12. (10.6) In the absence of ADH:
C. Without ADH, AQP2 stays in vesicles, water cannot leave the duct, and large volumes of dilute urine are excreted (as in diabetes insipidus).
13. (10.7) Aldosterone acts on the distal nephron to:
A. Aldosterone upregulates ENaC, ROMK, and the Na⁺/K⁺-ATPase in principal cells, causing Na⁺ (and thus water) retention while increasing K⁺ excretion.
14. (10.7) Atrial natriuretic peptide (ANP) is secreted in response to:
D. ANP opposes RAAS: it dilates the afferent arteriole, inhibits renin/aldosterone, and drives natriuresis, lowering blood volume and pressure.
15. (10.8) The rate-limiting enzyme released from the juxtaglomerular apparatus in response to low BP is:
C. JG cells sense low perfusion and sympathetic signals, releasing renin. ACE (in pulmonary endothelium) then converts ANG I to ANG II.
16. (10.8) Angiotensin II:
B. ANG II is a potent pressor. It also preferentially constricts the efferent arteriole to preserve GFR when renal perfusion is marginal.
17. (10.9) The Henderson-Hasselbalch equation for the blood buffer system shows that:
D. The lungs adjust ventilation fast; the kidneys adjust HCO₃⁻ slowly. Together they keep plasma pH near 7.4.
18. (10.9) Metabolic acidosis is compensated acutely by:
A. Kussmaul breathing in DKA is a classic example: rapid, deep breathing lowers PCO₂ and partially corrects the pH.
19. (10.10) The hypothalamus acts as the body's thermostat by:
B. The preoptic area senses blood temperature; the posterior hypothalamus triggers heat conservation; the anterior triggers heat loss.
20. (10.10) Shivering thermogenesis raises body temperature by:
C. Shivering converts chemical energy to heat rather than useful work. Brown adipose tissue (mainly in infants) adds non-shivering thermogenesis via UCP1 uncoupling.
21. (10.11) A hypertonic extracellular environment relative to the cell causes:
A. Water moves toward higher osmolarity. RBCs shrink in hypertonic saline and swell (and lyse) in hypotonic solutions.
22. (10.11) ADH release is triggered by:
D. Hypothalamic osmoreceptors detect hyperosmolarity; baroreceptors detect hypovolemia. Either triggers ADH release to conserve water.
23. (10.12) The primary nitrogenous waste in humans is:
C. Urea is water-soluble and far less toxic than ammonia. Terrestrial mammals can afford the water to excrete it.
24. (10.12) Uric acid is the primary nitrogenous waste in:
B. Uric acid minimizes water loss and is especially useful for egg-laying animals (waste can be stored inside the shell without toxicity).
