Take the NUMS Biology — Nervous and Chemical Coordination, Immunity (Set 3): 30 multiple-choice questions (40 minutes) with instant scoring and a full…
The first 5 questions of this test, with the correct answer and explanation.
Q1. During the rising phase of an action potential, the membrane potential changes rapidly because:
- A. Na⁺/K⁺ pumps pump Na⁺ in
- B. Cl⁻ channels close
- C. voltage-gated Na⁺ channels open and Na⁺ enters the axon ✓
- D. K⁺ channels open and K⁺ enters
Answer: C. voltage-gated Na⁺ channels open and Na⁺ enters the axon
Explanation: Depolarisation results from rapid Na⁺ influx; repolarisation follows as K⁺ leaves.
Q2. A local anaesthetic such as lidocaine blocks voltage-gated Na⁺ channels. The most likely effect is:
- A. K⁺ cannot leave neurons
- B. the resting potential becomes more positive
- C. neurotransmitter is destroyed
- D. action potentials cannot be generated or propagated in the pain fibres ✓
Answer: D. action potentials cannot be generated or propagated in the pain fibres
Explanation: Without Na⁺ influx there is no depolarisation, so pain impulses are blocked.
Q3. Myelinated axons conduct impulses faster because the action potential:
- A. jumps from one node of Ranvier to the next ✓
- B. travels along the myelin
- C. needs no Na⁺ channels
- D. spreads in both directions equally
Answer: A. jumps from one node of Ranvier to the next
Explanation: Saltatory conduction restricts depolarisation to the nodes, saving time and energy.
Q4. If a neuron is stimulated by a sub-threshold stimulus, the result is:
- A. a local graded potential that does not trigger an action potential ✓
- B. an action potential of reduced amplitude
- C. a smaller action potential
- D. hyperpolarisation always
Answer: A. a local graded potential that does not trigger an action potential
Explanation: Action potentials follow the all-or-none law; sub-threshold depolarisation dies out.
Q5. During the refractory period a second stimulus cannot produce another action potential because:
- A. Na⁺ channels are inactivated ✓
- B. myelin blocks the node
- C. all Na⁺ is outside the cell
- D. K⁺ has been depleted
Answer: A. Na⁺ channels are inactivated
Explanation: Inactivated voltage-gated Na⁺ channels cannot reopen until the membrane repolarises.
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Q6. Botulinum toxin causes muscle paralysis by:
- A. stimulating acetylcholinesterase
- B. preventing acetylcholine release from motor neuron terminals
- C. destroying myosin
- D. blocking Na⁺ channels in muscle
Q7. Organophosphate insecticides inhibit acetylcholinesterase. A farmer exposed to them would show:
- A. decreased salivation
- B. slower heart rate only
- C. continuous stimulation of muscles and glands
- D. muscle weakness from lack of transmitter
Q8. Which neurotransmitter is deficient in the substantia nigra of Parkinson's patients?
- A. GABA
- B. Serotonin
- C. Acetylcholine
- D. Dopamine
Q9. Which statement about the synapse is correct?
- A. Transmission is one-way because only the presynaptic neuron releases neurotransmitter
- B. Synapses use only electrical transmission in humans
- C. Impulses travel equally well in both directions
- D. The synaptic cleft is filled with a myelin sheath
Q10. Which brain region maintains balance and coordinates fine voluntary movements?
- A. Medulla
- B. Cerebellum
- C. Cerebrum
- D. Hypothalamus
Q11. Damage to the left side of the cerebral cortex responsible for speech production (Broca's area) leads to:
- A. difficulty in forming words although comprehension is largely retained
- B. loss of balance
- C. loss of vision
- D. inability to regulate temperature
Q12. In the reflex arc of the knee jerk, the sequence is:
- A. receptor → sensory neuron → motor neuron → effector
- B. effector → receptor
- C. sensory neuron → brain → effector
- D. receptor → motor neuron → sensory neuron
Q13. The sympathetic nervous system causes all of the following EXCEPT:
- A. increased heart rate
- B. increased peristalsis
- C. dilated pupils
- D. bronchodilation
Q14. Rods differ from cones in that rods:
- A. use three types of pigment
- B. are concentrated in the fovea
- C. are more sensitive to dim light and do not detect colour
- D. give sharp visual acuity
Q15. In a person with a deficiency of vitamin A, which condition is the earliest to appear?
- A. Glaucoma
- B. Night blindness
- C. Cataract
- D. Colour blindness
Q16. Insulin and glucagon act as antagonists. After a carbohydrate-rich meal, which change occurs?
- A. Glucagon rises
- B. Adrenaline rises
- C. Glycogen breakdown increases
- D. Insulin rises and glucose is taken up by muscle and liver
Q17. A person with type 1 diabetes forgets to take insulin. Which would be expected?
- A. Low blood glucose with hunger
- B. High blood glucose with ketone production
- C. Increased glycogen storage in the liver
- D. Reduced thirst and urine output
Q18. A tumour of the adrenal medulla producing excess adrenaline would cause:
- A. low blood glucose
- B. a slow heart rate
- C. weight gain from retention
- D. palpitations, raised blood pressure and sweating
Q19. Cortisol, released from the adrenal cortex in prolonged stress, causes:
- A. muscle protein synthesis
- B. increased immune activity
- C. decreased blood glucose
- D. increased gluconeogenesis and suppressed inflammation
Q20. Deficiency of iodine in the diet leads to goitre because:
- A. less thyroxine is made, so TSH enlarges the gland
- B. too much thyroxine is made by the gland
- C. the pituitary gland stops growing
- D. TSH is no longer secreted by the pituitary
Q21. Which pair of hormones acts antagonistically in regulating blood calcium?
- A. Insulin and thyroxine
- B. FSH and LH
- C. Oxytocin and ADH
- D. Calcitonin and parathyroid hormone
Q22. Oxytocin is released from the:
- A. thyroid
- B. anterior pituitary
- C. adrenal cortex
- D. posterior pituitary
Q23. Excess growth hormone in an adult after the epiphyseal plates have closed causes:
- A. acromegaly
- B. cretinism
- C. dwarfism
- D. gigantism
Q24. Steroid hormones act differently from peptide hormones because steroids:
- A. bind receptors on the cell surface with cAMP as the only messenger
- B. are destroyed in the blood
- C. never reach the nucleus
- D. pass through the membrane and bind intracellular receptors to alter gene expression
Q25. A plant growing towards light shows positive phototropism because auxin:
- A. accumulates on the lit side
- B. accumulates on the shaded side, promoting elongation
- C. stops being synthesised in the tip
- D. is destroyed in the shaded cells
Q26. Ethylene is used commercially to:
- A. promote stem elongation in lettuce
- B. delay leaf fall
- C. prolong dormancy of seeds
- D. ripen fruit uniformly
Q27. In vaccination, memory cells ensure that on re-exposure to the pathogen:
- A. no antibodies are produced
- B. only innate immunity operates
- C. the response is slower than the primary
- D. a faster and stronger secondary response occurs
Q28. Which immunoglobulin crosses the placenta to give passive immunity to a fetus?
Q29. In an allergic reaction, histamine is released by:
- A. neutrophils
- B. plasma cells directly
- C. mast cells after allergen binds IgE
- D. platelets only
Q30. A transplant recipient is given cyclosporine, which suppresses T-cell activation. The aim is to prevent:
- A. viral replication
- B. antibody secretion by memory B cells only
- C. graft rejection
- D. blood clotting