Take the NUMS Biology — Nervous and Chemical Coordination, Immunity (Set 1): 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. The resting membrane potential of a neuron (about −70 mV) is mainly due to:
- A. Rapid influx of Na⁺ ions
- B. Greater permeability of the membrane to K⁺ than Na⁺, with the Na⁺/K⁺ pump maintaining gradients ✓
- C. Equal permeability to Na⁺ and K⁺
- D. Influx of Ca²⁺ ions into the axon
Answer: B. Greater permeability of the membrane to K⁺ than Na⁺, with the Na⁺/K⁺ pump maintaining gradients
Explanation: K⁺ leaks out through open leak channels leaving the inside negative; the pump maintains the concentration gradients.
Q2. During the depolarisation phase of an action potential:
- A. Voltage-gated K⁺ channels open and K⁺ leaves
- B. Cl⁻ ions flood into the axon
- C. The Na⁺/K⁺ pump stops working permanently
- D. Voltage-gated Na⁺ channels open and Na⁺ rushes into the axon ✓
Answer: D. Voltage-gated Na⁺ channels open and Na⁺ rushes into the axon
Explanation: At threshold, Na⁺ channels open; influx makes the inside positive (~+30 to +40 mV). K⁺ efflux causes repolarisation.
Q3. During the absolute refractory period, a neuron cannot fire another action potential. This ensures that:
- A. Impulses travel in both directions
- B. Neurotransmitter is not released
- C. Impulses travel in one direction only along the axon ✓
- D. The axon remains permanently depolarised
Answer: C. Impulses travel in one direction only along the axon
Explanation: The region just behind an action potential cannot be re-excited, so the impulse moves forward only and impulses stay discrete.
Q4. Impulses travel faster along myelinated neurons because:
- A. Myelin increases ion flow across the entire membrane
- B. Myelinated axons have no Na⁺ channels at the nodes
- C. Myelin speeds up neurotransmitter release
- D. The action potential jumps between nodes of Ranvier (saltatory conduction) ✓
Answer: D. The action potential jumps between nodes of Ranvier (saltatory conduction)
Explanation: Myelin insulates the axon; depolarisation occurs only at the nodes, so the impulse leaps from node to node.
Q5. In multiple sclerosis, the immune system destroys myelin in the CNS. The most direct effect on neurons is:
- A. Formation of new nodes of Ranvier
- B. Slowed or blocked conduction of nerve impulses ✓
- C. Increased neurotransmitter synthesis
- D. Faster conduction of impulses
Answer: B. Slowed or blocked conduction of nerve impulses
Explanation: Loss of myelin prevents saltatory conduction, slowing or blocking signals and causing weakness and sensory problems.
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Q6. A stimulus stronger than threshold is applied to a neuron. Compared with a threshold stimulus, it produces:
- A. No action potentials
- B. Larger action potentials
- C. Action potentials of the same size but at a higher frequency
- D. Action potentials that travel more slowly
Q7. At a cholinergic synapse, the arrival of an action potential at the presynaptic terminal causes:
- A. Efflux of K⁺, releasing acetylcholine
- B. Direct electrical flow to the next neuron
- C. Influx of Ca²⁺, which triggers exocytosis of acetylcholine
- D. Breakdown of acetylcholine by cholinesterase
Q8. Certain organophosphate insecticides inhibit acetylcholinesterase. What happens at affected synapses?
- A. Acetylcholine accumulates and the postsynaptic membrane is continuously stimulated
- B. Acetylcholine release stops completely
- C. Postsynaptic receptors are destroyed
- D. Impulses travel faster in the presynaptic neuron
Q9. Synapses ensure one-way transmission because:
- A. Postsynaptic neurons contain vesicles
- B. Neurotransmitter is released only from the presynaptic side and receptors are only on the postsynaptic side
- C. Synaptic clefts are filled with myelin
- D. Impulses travel in both directions along dendrites
Q10. A patient has damage to the cerebellum. Which symptom is most likely?
- A. Loss of balance and poorly coordinated movements
- B. Complete loss of memory
- C. Inability to regulate body temperature
- D. Loss of the sense of smell
Q11. Which part of the brain controls involuntary functions such as breathing rate and heart rate?
- A. Cerebellum
- B. Thalamus
- C. Cerebrum
- D. Medulla oblongata
Q12. Withdrawing the hand quickly from a hot plate before feeling pain involves a reflex arc. The correct pathway is:
- A. Receptor → sensory neuron → interneuron in spinal cord → motor neuron → effector
- B. Receptor → interneuron → sensory neuron → muscle
- C. Receptor → motor neuron → brain → sensory neuron → effector
- D. Effector → sensory neuron → spinal cord → receptor
Q13. Which effect is produced by stimulation of the sympathetic nervous system?
- A. Increased peristalsis and salivation
- B. Constriction of bronchioles
- C. Dilation of pupils and increased heart rate
- D. Constriction of pupils and slower heart rate
Q14. Parkinson's disease is associated with the degeneration of neurons that produce:
- A. Dopamine
- B. Acetylcholine in the spinal cord
- C. Serotonin in the gut
- D. Insulin
Q15. Alzheimer's disease is characterised mainly by:
- A. Loss of balance due to cerebellar damage
- B. Progressive loss of memory due to plaques and tangles in the brain
- C. Sudden paralysis of one side of the body
- D. Seizures caused by excess myelin
Q16. Steroid hormones such as cortisol act on target cells by:
- A. Binding membrane receptors and activating cAMP only
- B. Opening Na⁺ channels directly
- C. Being broken down outside the cell
- D. Passing through the cell membrane and binding intracellular receptors that regulate gene expression
Q17. Adrenaline, a water-soluble hormone, increases glycogen breakdown in liver cells by:
- A. Binding a membrane receptor and activating cAMP as a second messenger
- B. Entering the nucleus directly to alter genes
- C. Dissolving the cell membrane
- D. Acting as an enzyme itself
Q18. After a carbohydrate-rich meal, blood glucose rises. The pancreas responds by:
- A. Releasing glucagon from α-cells to raise glucose further
- B. Stopping all hormone secretion
- C. Releasing insulin from β-cells, increasing glucose uptake and glycogen formation
- D. Releasing ADH
Q19. A child shows stunted growth and mental retardation due to deficiency of a hormone from birth. The hormone is most likely:
- A. Thyroxine
- B. Oxytocin
- C. Insulin
- D. Adrenaline
Q20. An adult with excess growth hormone after the growth plates have fused develops:
- A. Gigantism with very tall stature
- B. Cretinism
- C. Acromegaly, with enlarged hands, feet and jaw
- D. Dwarfism
Q21. Lack of iodine in the diet causes the thyroid gland to enlarge (goitre) because:
- A. Parathormone levels fall
- B. Excess thyroxine is produced
- C. Iodine directly causes cell division in the thyroid
- D. Low thyroxine reduces negative feedback, so excess TSH stimulates the thyroid to grow
Q22. Parathormone raises blood calcium levels. Which hormone has the opposite effect?
- A. Glucagon
- B. Calcitonin
- C. Thyroxine
- D. Aldosterone
Q23. Oxytocin release during childbirth is an example of positive feedback because:
- A. Uterine contractions stimulate more oxytocin release, which intensifies contractions
- B. It keeps contractions constant
- C. It inhibits prolactin secretion
- D. Oxytocin reduces contractions to a normal level
Q24. Plant hormone abscisic acid (ABA) is released during drought. Its main effect is to:
- A. Break seed dormancy
- B. Stimulate stem elongation
- C. Cause closure of stomata to reduce water loss
- D. Promote fruit ripening
Q25. A shoot bends towards light because auxin:
- A. Accumulates on the shaded side, causing those cells to elongate more
- B. Inhibits cell growth on both sides equally
- C. Accumulates on the lit side, causing those cells to elongate more
- D. Is destroyed on the shaded side
Q26. A person vaccinated against hepatitis B has antibodies on exposure. This type of immunity is:
- A. Artificially acquired active immunity
- B. Artificially acquired passive immunity
- C. Naturally acquired passive immunity
- D. Innate immunity
Q27. A newborn gets antibodies from the mother through the placenta and breast milk. This provides:
- A. Naturally acquired passive immunity that is short-lived
- B. Artificially acquired active immunity
- C. Cell-mediated immunity
- D. Lifelong active immunity
Q28. The secondary immune response is faster and stronger than the primary response because of:
- A. Memory cells produced during the first exposure
- B. Higher body temperature
- C. More red blood cells
- D. Antibiotics stored in the body
Q29. Which cells are mainly responsible for cell-mediated immunity and directly kill virus-infected cells?
- A. Cytotoxic T lymphocytes
- B. Plasma cells
- C. Erythrocytes
- D. Mast cells
Q30. An antibody molecule binds a specific antigen through its:
- A. Constant region of the heavy chain only
- B. Hinge region
- C. Disulphide bonds
- D. Variable regions at the tips of the heavy and light chains