Nerve impulse MCQs With Answer

Nerve impulse MCQs With Answer are essential study tools for B. Pharm students preparing for pharmacology, physiology, and therapeutics exams. This concise, keyword-rich introduction focuses on nerve impulse concepts such as action potential, resting membrane potential, ion channels, saltatory conduction, refractory periods, synaptic transmission, and pharmacological modulators like local anesthetics and channel blockers. These MCQs emphasize clinical relevance and drug mechanisms that target neuronal excitability, making them ideal for deepening understanding and improving recall. Questions cover ionic bases, electrophysiology models, conduction properties, and drug interactions with channels and receptors. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which ion primarily determines the resting membrane potential in neurons?

• Calcium (Ca2+)
• Potassium (K+)
• Sodium (Na+)
• Chloride (Cl-)

Correct Answer: Potassium (K+)

Q2. The Nernst equation is used to calculate which of the following?

• Membrane capacitance
• Equilibrium potential for a single ion
• Total ionic current through the membrane
• Membrane time constant

Correct Answer: Equilibrium potential for a single ion

Q3. The rapid upstroke (phase 0) of a neuronal action potential is mainly due to:

• Opening of voltage-gated K+ channels
• Opening of voltage-gated Na+ channels
• Activation of Na+/K+ ATPase
• Increased Cl- conductance

Correct Answer: Opening of voltage-gated Na+ channels

Q4. The absolute refractory period of an action potential is primarily caused by:

• Delayed opening of K+ channels
• Inactivation of voltage-gated Na+ channels
• Activation of Na+/K+ pump
• Increased membrane capacitance

Correct Answer: Inactivation of voltage-gated Na+ channels

Q5. Saltatory conduction refers to action potential propagation that:

• Occurs continuously along unmyelinated axons
• Jumps between nodes of Ranvier in myelinated axons
• Depends on synaptic transmission between segments
• Is slower than conduction in unmyelinated fibers

Correct Answer: Jumps between nodes of Ranvier in myelinated axons

Q6. The primary role of the node of Ranvier is to:

• Insulate the axon electrically
• Store neurotransmitters
• Regenerate the action potential via high density of ion channels
• Decrease internodal capacitance

Correct Answer: Regenerate the action potential via high density of ion channels

Q7. Myelination increases conduction velocity chiefly by:

• Increasing membrane capacitance and decreasing resistance
• Increasing membrane resistance and decreasing capacitance
• Increasing internal resistance of the axon
• Enhancing neurotransmitter release at nodes

Correct Answer: Increasing membrane resistance and decreasing capacitance

Q8. The length constant (lambda) is increased by which change?

• Decreased membrane resistance
• Increased internal (axial) resistance
• Increased membrane resistance
• Increased membrane capacitance

Correct Answer: Increased membrane resistance

Q9. Local anesthetics produce analgesia primarily by:

• Blocking voltage-gated calcium channels
• Blocking voltage-gated potassium channels
• Blocking voltage-gated sodium channels
• Enhancing GABAergic transmission

Correct Answer: Blocking voltage-gated sodium channels

Q10. Tetrodotoxin (TTX) causes paralysis by binding to and blocking which channel?

• Voltage-gated K+ channels
• Voltage-gated Na+ channels
• Ligand-gated NMDA receptors
• Voltage-gated Ca2+ channels

Correct Answer: Voltage-gated Na+ channels

Q11. Hyperkalemia (elevated extracellular K+) on neuronal membranes typically causes:

• Hyperpolarization, making firing less likely
• Depolarization, making the resting potential less negative
• No change in membrane potential
• Increased chloride conductance

Correct Answer: Depolarization, making the resting potential less negative

Q12. During the relative refractory period, an action potential can be initiated if:

• No additional stimulus is applied
• A weaker than normal stimulus is applied
• A stronger than normal stimulus is applied
• Only hyperpolarizing current is applied

Correct Answer: A stronger than normal stimulus is applied

Q13. The Hodgkin-Huxley model provides a quantitative description of:

• Synaptic vesicle recycling
• Ionic currents and gating variables underlying the action potential
• Neurotransmitter receptor subtypes
• Long-term synaptic plasticity mechanisms

Correct Answer: Ionic currents and gating variables underlying the action potential

Q14. Demyelination of an axon would most likely cause which effect on conduction safety factor?

• Increase safety factor
• No change in safety factor
• Decrease safety factor
• Completely eliminate ionic currents

Correct Answer: Decrease safety factor

Q15. Voltage-gated K+ channels mainly contribute to which phase of the action potential?

• Depolarization phase
• Repolarization and afterhyperpolarization
• Resting membrane potential generation via pumps
• Fast sodium inactivation

Correct Answer: Repolarization and afterhyperpolarization

Q16. Which of the following is an advantage of saltatory conduction?

• Decreased conduction velocity
• Higher energy consumption
• Faster conduction with lower energy cost
• Continuous regeneration that uses more ATP

Correct Answer: Faster conduction with lower energy cost

Q17. A compound action potential recorded from a peripheral nerve represents:

• The ionic current through a single neuron
• The summed action potentials of many axons in the nerve
• Only the conduction in motor fibers
• A measure of synaptic potentials at the neuromuscular junction

Correct Answer: The summed action potentials of many axons in the nerve

Q18. Myelin in the peripheral nervous system is produced by which cells?

• Microglia
• Oligodendrocytes
• Schwann cells
• Astrocytes

Correct Answer: Schwann cells

Q19. Neuronal threshold refers to the membrane potential at which:

• The neuron becomes refractory permanently
• An action potential is triggered due to net inward current
• Sodium channels close and potassium channels open
• Synaptic vesicles are released

Correct Answer: An action potential is triggered due to net inward current

Q20. Accommodation in a nerve fiber is best described as:

• Increased excitability during rapid stimulation
• Progressive decrease in excitability with sustained subthreshold depolarization
• Immediate firing in response to any depolarizing pulse
• Failure of Na+/K+ pump

Correct Answer: Progressive decrease in excitability with sustained subthreshold depolarization

Q21. Lidocaine exhibits use-dependent block of sodium channels because it:

• Binds preferentially to closed channels
• Binds preferentially to open or inactivated channels
• Increases channel conductance
• Blocks potassium channels instead

Correct Answer: Binds preferentially to open or inactivated channels

Q22. An excitatory postsynaptic potential (EPSP) is typically produced by increased conductance to which ion?

• Chloride (Cl-)
• Potassium (K+)
• Sodium (Na+)
• Calcium pump activity

Correct Answer: Sodium (Na+)

Q23. An inhibitory postsynaptic potential (IPSP) commonly results from increased permeability to:

• Sodium (Na+)
• Potassium (K+) or chloride (Cl-)
• Glucose
• Sodium-potassium pump activation only

Correct Answer: Potassium (K+) or chloride (Cl-)

Q24. NMDA-type glutamate receptors differ from AMPA receptors because NMDA receptors:

• Are purely ligand-gated with no voltage dependence
• Require both ligand binding and depolarization to remove Mg2+ block and are permeable to Ca2+
• Are selective only for K+
• Are inhibitory receptors producing IPSPs

Correct Answer: Require both ligand binding and depolarization to remove Mg2+ block and are permeable to Ca2+

Q25. The Na+/K+ ATPase contributes to nerve function by:

• Generating action potentials directly
• Maintaining Na+ and K+ concentration gradients using ATP
• Allowing passive diffusion of ions
• Creating gap junctions between neurons

Correct Answer: Maintaining Na+ and K+ concentration gradients using ATP

Q26. Increasing membrane capacitance in an axon will:

• Speed up the rate of voltage change
• Slow the rate of voltage change
• Have no effect on membrane dynamics
• Reduce internal resistance only

Correct Answer: Slow the rate of voltage change

Q27. The membrane time constant (tau) is defined as:

• Membrane resistance divided by membrane capacitance
• Membrane capacitance divided by membrane resistance
• Membrane resistance multiplied by membrane capacitance
• Internal resistance multiplied by axon length

Correct Answer: Membrane resistance multiplied by membrane capacitance

Q28. Which statement best describes the “all-or-none” principle of action potentials?

• Action potential amplitude increases with stronger stimulus
• Action potentials occur only in motor neurons
• Once threshold is reached, an action potential of fixed amplitude is produced
• Action potentials summate linearly to produce a larger spike

Correct Answer: Once threshold is reached, an action potential of fixed amplitude is produced

Q29. The voltage-clamp technique is primarily used to:

• Measure membrane capacitance only
• Record ionic currents while holding membrane potential constant
• Visualize single ion channels directly
• Measure neurotransmitter concentrations

Correct Answer: Record ionic currents while holding membrane potential constant

Q30. The patch-clamp technique is especially valuable because it can:

• Measure whole-brain electrical activity noninvasively
• Record currents from single ion channels with high resolution
• Replace the need for voltage clamp
• Image ion channel structure directly

Correct Answer: Record currents from single ion channels with high resolution

Q31. Botulinum toxin causes flaccid paralysis by:

• Blocking voltage-gated Na+ channels
• Cleaving SNARE proteins and preventing acetylcholine release
• Inhibiting the Na+/K+ pump
• Activating GABA receptors

Correct Answer: Cleaving SNARE proteins and preventing acetylcholine release

Q32. The synaptic delay at a chemical synapse is mainly due to:

• Axonal conduction time only
• Diffusion of neurotransmitter across the synaptic cleft and vesicle fusion processes
• The time for postsynaptic action potential generation exclusively
• Reuptake of neurotransmitter into the presynaptic terminal

Correct Answer: Diffusion of neurotransmitter across the synaptic cleft and vesicle fusion processes

Q33. Fast ionotropic synaptic transmission is mediated by:

• G-protein coupled receptors
• Ion channel-linked receptors such as AMPA receptors
• Intracellular second messengers only
• Changes in gene transcription

Correct Answer: Ion channel-linked receptors such as AMPA receptors

Q34. Metabotropic receptors typically produce their effects by:

• Directly forming ion channels that open instantaneously
• Activating G-proteins and second messenger cascades
• Blocking axonal conduction physically
• Causing immediate membrane depolarization only

Correct Answer: Activating G-proteins and second messenger cascades

Q35. Conduction velocity is generally higher in axons that are:

• Small diameter and unmyelinated
• Large diameter and myelinated
• Small diameter and myelinated
• Large diameter and unmyelinated

Correct Answer: Large diameter and myelinated

Q36. Multiple sclerosis primarily affects which of the following?

• Peripheral nerve Schwann cell myelin
• Central nervous system oligodendrocyte myelin
• Neuromuscular junction acetylcholine receptors
• Voltage-gated sodium channels exclusively

Correct Answer: Central nervous system oligodendrocyte myelin

Q37. The absolute refractory period limits the maximum:

• Amplitude of action potentials
• Duration of synaptic vesicle release
• Firing frequency of a neuron
• Size of the axon

Correct Answer: Firing frequency of a neuron

Q38. Afterhyperpolarization following an action potential is mainly mediated by:

• Fast inward sodium currents
• Increased potassium conductance
• Chloride influx through NMDA receptors
• Immediate activation of Na+/K+ pump alone

Correct Answer: Increased potassium conductance

Q39. Fast inactivation of voltage-gated sodium channels during an action potential is due to:

• Closure of the activation gate
• Opening of an inactivation gate that blocks the pore
• Permanent channel degradation
• Immediate potassium channel opening only

Correct Answer: Opening of an inactivation gate that blocks the pore

Q40. Which fiber type conducts action potentials fastest?

• Small unmyelinated fibers (C fibers)
• Small myelinated sensory fibers
• Large myelinated motor fibers (A-alpha)
• Large unmyelinated fibers

Correct Answer: Large myelinated motor fibers (A-alpha)

Q41. Potassium channel selectivity for K+ ions is primarily achieved by:

• ATP binding to the channel pore
• A selectivity filter that coordinates dehydrated K+ ions
• Blocking Na+ by internal Mg2+
• Voltage-sensing S4 segments only

Correct Answer: A selectivity filter that coordinates dehydrated K+ ions

Q42. Use-dependent block of sodium channels by antiarrhythmic drugs means the drug:

• Preferentially binds to resting closed channels
• Preferentially binds to channels during repetitive activation
• Only binds to potassium channels
• Enhances sodium currents during high-frequency firing

Correct Answer: Preferentially binds to channels during repetitive activation

Q43. Inhibition of presynaptic voltage-gated Ca2+ channels will primarily cause:

• Increased neurotransmitter release
• Decreased neurotransmitter release
• No effect on synaptic transmission
• Enhanced postsynaptic receptor sensitivity

Correct Answer: Decreased neurotransmitter release

Q44. Nodes of Ranvier are enriched in which channels to enable saltatory conduction?

• Ligand-gated Cl- channels
• Voltage-gated Na+ channels
• Voltage-gated Ca2+ channels only
• High density of Na+/K+ pumps exclusively

Correct Answer: Voltage-gated Na+ channels

Q45. Which toxin is well-known for blocking neuronal voltage-gated sodium channels?

• Tetrodotoxin (TTX)
• Curare
• Strychnine
• Atropine

Correct Answer: Tetrodotoxin (TTX)

Q46. Excitatory synapses typically produce which change in the postsynaptic membrane?

• Hyperpolarization via Cl- influx
• Depolarization by increasing Na+ conductance
• Permanent membrane depolarization
• Immediate axonal branching

Correct Answer: Depolarization by increasing Na+ conductance

Q47. In peripheral nerve conduction studies, demyelination is expected to cause:

• Decreased latency and increased amplitude
• Increased latency and possible conduction block
• No change in conduction velocity
• Only changes in synaptic delay

Correct Answer: Increased latency and possible conduction block

Q48. The safety factor for conduction is best defined as:

• The ratio of axon diameter to myelin thickness
• The margin of current available to depolarize the next node to threshold
• The absolute refractory period duration
• The amount of neurotransmitter released per impulse

Correct Answer: The margin of current available to depolarize the next node to threshold

Q49. The alpha subunit of voltage-gated sodium channels is important because it:

• Forms the ion-conducting pore and gating machinery
• Is purely regulatory with no pore function
• Is only present in cardiac tissue
• Is responsible for vesicle docking at synapses

Correct Answer: Forms the ion-conducting pore and gating machinery

Q50. A common pharmacological target for many antiepileptic drugs is which mechanism?

• Enhancement of voltage-gated sodium channel activity
• Blocking GABAergic transmission
• Inhibition of voltage-gated sodium channels or enhancement of GABAergic inhibition
• Activation of NMDA receptors to increase excitability

Correct Answer: Inhibition of voltage-gated sodium channels or enhancement of GABAergic inhibition

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com