Take the NUMS Biology — Homeostasis, Support and Movement (Set 4): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer…
The first 5 questions of this test, with the correct answer and explanation.
Q1. Inulin is filtered but neither reabsorbed nor secreted. In a patient, urine inulin is 30 mg/mL, urine flow is 1.2 mL/min and plasma inulin is 0.3 mg/mL. What is the GFR?
- A. 36 mL/min
- B. 12 mL/min
- C. 120 mL/min ✓
- D. 300 mL/min
Answer: C. 120 mL/min
Explanation: GFR = (urine conc × urine flow) ÷ plasma conc = (30 × 1.2) ÷ 0.3 = 120 mL/min.
Q2. An adult filters about 180 L of filtrate per day and excretes 1.5 L of urine. Approximately what percentage of filtered water is reabsorbed?
- A. 75%
- B. 99% ✓
- C. 90%
- D. 50%
Answer: B. 99%
Explanation: (180 − 1.5) ÷ 180 × 100 ≈ 99.2%, mostly in the proximal tubule, loop of Henle and collecting duct.
Q3. Plasma glucose is 200 mg/100 mL and GFR is 100 mL/min. The tubular maximum for glucose is 150 mg/min. How much glucose appears in urine per minute?
- A. 200 mg
- B. 150 mg
- C. 0 mg
- D. 50 mg ✓
Answer: D. 50 mg
Explanation: Filtered = 200 mg/100 mL × 100 mL/min = 200 mg/min; reabsorbed at most 150 mg/min; the 50 mg/min excess is excreted.
Q4. A patient passes 15 L per day of very dilute urine that contains no glucose. Water intake is high and urine does not concentrate even after water deprivation. The most likely cause is
- A. deficiency or non-response to ADH ✓
- B. damaged glomeruli with protein loss
- C. excess aldosterone
- D. insulin deficiency
Answer: A. deficiency or non-response to ADH
Explanation: Diabetes insipidus: without functional ADH the collecting duct stays impermeable to water, causing large volumes of dilute urine; in diabetes mellitus the urine contains glucose.
Q5. Furosemide blocks Na⁺/K⁺/2Cl⁻ transport in the thick ascending limb of the loop of Henle. Which effect is expected?
- A. Medullary gradient decreases, so urine is more dilute and larger in volume ✓
- B. Medullary gradient increases, giving concentrated urine
- C. Urine volume falls
- D. Water reabsorption rises in the descending limb
Answer: A. Medullary gradient decreases, so urine is more dilute and larger in volume
Explanation: Salt pumping in the ascending limb builds the medullary osmotic gradient; blocking it reduces water reabsorption from the collecting duct, increasing urine flow (a diuretic).
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Q6. A patient with adrenal cortex failure (Addison's disease) is expected to show
- A. high blood sodium and high blood volume
- B. high blood sodium and low blood potassium
- C. low blood potassium only
- D. low blood sodium and raised blood potassium
Q7. A fall in blood pressure leads to renin release by the juxtaglomerular cells. Which sequence follows?
- A. Angiotensinogen → angiotensin → aldosterone release → more Na⁺ and water retention
- B. Angiotensin → ADH inhibition → more dilute urine and a further fall in blood volume
- C. Aldosterone → renin release → less Na⁺ reabsorption in the distal tubule and more urine
- D. Renin → insulin release → water retention by the collecting duct and a rise in blood volume
Q8. Constriction of the efferent arteriole (with afferent unchanged) causes
- A. blockage of the loop of Henle and the collecting duct
- B. an increase in glomerular capillary pressure and GFR
- C. a decrease in glomerular capillary pressure and GFR
- D. no change in either glomerular pressure or GFR
Q9. A patient's urine contains protein and red blood cells but no glucose. Which part is most likely damaged?
- A. The loop of Henle
- B. The collecting duct ADH receptors
- C. The proximal tubule glucose transporters
- D. The glomerular filtration barrier
Q10. Marine bony fish live in water more concentrated than their body fluids. Which set of adaptations applies?
- A. Absorb salts actively through the gills and excrete large volumes of dilute urine
- B. Drink seawater, excrete salt through the gills and produce little concentrated urine
- C. Drink no water, absorb salts through the gills and produce large volumes of dilute urine
- D. Drink seawater and produce large volumes of dilute urine to remove the excess water
Q11. Freshwater fish, in contrast to marine fish, mainly
- A. produce large volumes of dilute urine and absorb salts through the gills
- B. produce small volumes of concentrated urine and drink seawater to replace losses
- C. drink large amounts of water and excrete excess salt through the gills
- D. excrete salt through the gills and produce small volumes of concentrated urine
Q12. Birds and reptiles that lay shelled eggs excrete nitrogen mainly as uric acid. What is the main advantage?
- A. It is highly toxic, which kills pathogens in the egg and so protects the embryo
- B. It is nearly insoluble, so it needs little water and is stored harmlessly in the egg
- C. It is more soluble than urea, so it dissolves in the egg fluid and is carried away
- D. It needs more energy to make than urea, and the extra heat warms the developing egg
Q13. Core temperature rises during an infection when pyrogens reset the hypothalamic set point upwards. Early in the fever the person feels cold and shivers because
- A. sweating has been triggered and evaporation is cooling the skin below the original set point
- B. the body temperature is below the new set point, so heat-generating responses are activated
- C. the body temperature is above the new set point, so heat-loss responses such as vasodilation start
- D. thermoreceptors in the skin stop working during infection, so the brain cannot detect temperature
Q14. Which response occurs when a person moves from a warm room into a cold room?
- A. Decreased heat production and increased heat loss
- B. Vasodilation of skin arterioles and sweating
- C. Decreased metabolic rate and relaxed muscles
- D. Vasoconstriction of skin arterioles, shivering and release of thyroxine
Q15. Oxygen consumption of animal X rises as the environmental temperature falls below 20 °C, but oxygen consumption of animal Y falls as the environmental temperature falls. Which is the correct interpretation?
- A. Both are endotherms
- B. Both are ectotherms
- C. X is an ectotherm and Y an endotherm
- D. X is an endotherm and Y an ectotherm
Q16. Which is an example of positive feedback?
- A. Insulin release lowering blood glucose, which then switches off further insulin secretion
- B. ADH release when plasma becomes concentrated, which restores the water potential of blood
- C. Oxytocin-induced uterine contractions stimulating more oxytocin release during labour
- D. Sweating after a rise in body temperature, which lowers it back towards the set point
Q17. A sarcomere is 2.2 μm long when relaxed and its A band is 1.6 μm. When the muscle contracts so that the sarcomere is 1.8 μm, what is the I band and A band?
- A. I band 0.6 μm; A band 1.6 μm
- B. I band 0.2 μm; A band 1.2 μm
- C. I band 0.2 μm; A band remains 1.6 μm
- D. I band 0.6 μm; A band 1.2 μm
Q18. Shortly after death, muscles become stiff (rigor mortis). The cause is
- A. lack of ATP, so myosin heads cannot detach from actin
- B. excess ATP binding to actin
- C. breakdown of the actin filaments
- D. calcium being pumped out of the sarcoplasmic reticulum
Q19. In a muscle fibre, which event directly allows myosin to bind to actin?
- A. Acetylcholine binds to actin, exposing the myosin-binding sites on the filament
- B. Troponin binds to myosin heads, pulling the myosin onto the actin filament
- C. ATP binds to tropomyosin, moving it off the myosin-binding sites on actin
- D. Calcium binds troponin, moving tropomyosin off the myosin-binding sites
Q20. Botulinum toxin blocks acetylcholine release at neuromuscular junctions. Which result is expected?
- A. Flaccid paralysis, because the muscle fibre is not depolarised
- B. Continuous contraction, because calcium is released
- C. Spastic paralysis, because acetylcholine accumulates
- D. Increased muscle tone
Q21. A sprinter's muscle contracts forcefully for 8 seconds. Which immediate source regenerates ATP fastest in this time?
- A. Glycogen in the liver
- B. Aerobic oxidation of fat
- C. Creatine phosphate
- D. Protein breakdown
Q22. A tissue consists of spindle-shaped cells with a single central nucleus, lacking striations, and contracts slowly and involuntarily. It is most likely found in
- A. the diaphragm
- B. the wall of the intestine
- C. the biceps muscle
- D. the heart wall
Q23. Which pair of structures is correctly matched?
- A. Tendon and ligament: both connect muscle to muscle
- B. Ligament: connects muscle to bone; tendon: lines joint cavities
- C. Tendon: connects muscle to bone; ligament: connects bone to bone
- D. Tendon: connects bone to bone; ligament: connects muscle to bone
Q24. Children in a region with little sunlight and a diet low in vitamin D show bowed legs. This condition and its cause are
- A. osteoporosis, with excess bone resorption after menopause
- B. arthritis, with immune attack on synovium
- C. rickets, with inadequate calcium absorption and bone mineralisation
- D. gout, with uric acid deposits
Q25. Why does damaged hyaline cartilage heal very slowly compared with bone?
- A. It is richly supplied with nerves, so pain stops the joint from being used
- B. It is made of mineralised calcium phosphate, which is brittle and cannot be repaired
- C. It has no blood supply, so nutrients reach the chondrocytes only by diffusion
- D. It contains no living cells, so no new matrix can be made after injury
Q26. The adult human axial skeleton includes the skull (22 bones), ear ossicles (6), hyoid (1), vertebral column (26) and the thoracic cage (25). How many bones form it?
Q27. Strings in celery stalks are strong and flexible and the cells at the corners have thickened walls of cellulose and pectin but remain alive. These cells are
- A. tracheids
- B. collenchyma
- C. sclerenchyma fibres
- D. parenchyma
Q28. A herbaceous plant wilts on a hot afternoon but recovers after watering. Why does it recover?
- A. Cells regain turgor, restoring the pressure that supports non-woody tissues
- B. Xylem vessels are converted into sclerenchyma, which stiffens the stem within minutes
- C. Stomata open to take in more water from the air, which refills the cells
- D. Lignin is rapidly synthesised in the stem, restoring rigidity to the wilted tissues
Q29. Turning the head to say 'no' occurs at a joint between the atlas and axis vertebrae. What type of joint is it?
- A. Hinge joint
- B. Ball-and-socket joint
- C. Pivot joint
- D. Gliding joint
Q30. During forearm flexion, which description of the muscles is correct?
- A. Biceps relaxes as the antagonist while the triceps contracts as the prime mover
- B. Biceps contracts as the prime mover while triceps relaxes as its antagonist
- C. Biceps lengthens as the prime mover while triceps shortens as the antagonist
- D. Both muscles contract equally as synergists to hold the elbow joint steady