UTSC NROB61 Neurophysiology: Exam 1 - Questions with
Correct Answers
50 questions
1. Invertebrate preparations such as the leech are useful because:
A. Neurons are large and individually identifiable
B. They have no synapses
C. They lack ion channels
D. They have no behavior
Correct Answer: A. Neurons are large and individually identifiable
Rationale: The same neuron can be found in every animal.
2. The overshoot of an action potential is the portion where:
A. Vm is below rest
B. Na+ channels are inactivated only
C. Vm is positive
D. Vm equals EK
Correct Answer: C. Vm is positive
Rationale: The inside briefly becomes positive.
3. Which structure increases the speed of axonal conduction?
A. Dendritic spines
B. Myelin
C. Golgi apparatus
D. Microglia
Correct Answer: B. Myelin
Rationale: Myelin allows saltatory conduction.
4. Labeled-line coding means that:
A. All sensations travel in one fiber
B. The pathway activated determines the perceived modality
C. Firing rate encodes modality
D. Neurons change modality with learning
Correct Answer: B. The pathway activated determines the perceived modality
Rationale: E.g., activating an optic nerve fiber is perceived as light.
5. A gigaohm seal is important because it:
A. Increases membrane capacitance
B. Opens channels
C. Depolarizes the cell
D. Reduces noise and isolates the patch electrically
Correct Answer: D. Reduces noise and isolates the patch electrically
Rationale: Leak current is minimal.
6. Cyclic nucleotide-gated (CNG) channels are important in:
A. Photoreceptors and olfactory neurons
B. Skeletal muscle contraction only
C. Myelination
D. Synaptic vesicle fusion
Correct Answer: A. Photoreceptors and olfactory neurons
Rationale: cGMP gates the rod channel.
, 7. In which patch configuration is the cytoplasmic face of the membrane exposed to the bath?
A. Outside-out
B. Inside-out
C. Cell-attached
D. Whole-cell
Correct Answer: B. Inside-out
Rationale: Useful for applying second messengers.
8. The selectivity filter of K+ channels contains the signature sequence:
A. DEKA
B. EEEE
C. TVGYG
D. GGGG
Correct Answer: C. TVGYG
Rationale: Carbonyl oxygens mimic K+ hydration shell.
9. [Ca2+]out = 2 mM and [Ca2+]in = 0.0001 mM at 37 C. ECa is about:
A. +264 mV
B. +132 mV
C. -132 mV
D. +61 mV
Correct Answer: B. +132 mV
Rationale: 30.75 x log10(20,000) = 132 mV.
10. Only a tiny number of ions need to cross the membrane to set the resting potential because:
A. Ions are very large
B. Ion channels are rare
C. The pump stores charge
D. The membrane capacitance is small relative to cell volume
Correct Answer: D. The membrane capacitance is small relative to cell volume
Rationale: Bulk concentrations barely change.
11. If the Na+/K+ pump is blocked with ouabain, the resting potential will:
A. Immediately collapse to 0 mV
B. Slowly depolarize as gradients run down
C. Hyperpolarize
D. Stay the same forever
Correct Answer: B. Slowly depolarize as gradients run down
Rationale: Gradients dissipate over minutes to hours.
12. [Cl-]out = 110 mM and [Cl-]in = 10 mM at 37 C. ECl is about:
A. +64 mV
B. -89 mV
C. 0 mV
D. -64 mV
Correct Answer: D. -64 mV
Rationale: For z = -1, E = -61.5 x log10(110/10).
Correct Answers
50 questions
1. Invertebrate preparations such as the leech are useful because:
A. Neurons are large and individually identifiable
B. They have no synapses
C. They lack ion channels
D. They have no behavior
Correct Answer: A. Neurons are large and individually identifiable
Rationale: The same neuron can be found in every animal.
2. The overshoot of an action potential is the portion where:
A. Vm is below rest
B. Na+ channels are inactivated only
C. Vm is positive
D. Vm equals EK
Correct Answer: C. Vm is positive
Rationale: The inside briefly becomes positive.
3. Which structure increases the speed of axonal conduction?
A. Dendritic spines
B. Myelin
C. Golgi apparatus
D. Microglia
Correct Answer: B. Myelin
Rationale: Myelin allows saltatory conduction.
4. Labeled-line coding means that:
A. All sensations travel in one fiber
B. The pathway activated determines the perceived modality
C. Firing rate encodes modality
D. Neurons change modality with learning
Correct Answer: B. The pathway activated determines the perceived modality
Rationale: E.g., activating an optic nerve fiber is perceived as light.
5. A gigaohm seal is important because it:
A. Increases membrane capacitance
B. Opens channels
C. Depolarizes the cell
D. Reduces noise and isolates the patch electrically
Correct Answer: D. Reduces noise and isolates the patch electrically
Rationale: Leak current is minimal.
6. Cyclic nucleotide-gated (CNG) channels are important in:
A. Photoreceptors and olfactory neurons
B. Skeletal muscle contraction only
C. Myelination
D. Synaptic vesicle fusion
Correct Answer: A. Photoreceptors and olfactory neurons
Rationale: cGMP gates the rod channel.
, 7. In which patch configuration is the cytoplasmic face of the membrane exposed to the bath?
A. Outside-out
B. Inside-out
C. Cell-attached
D. Whole-cell
Correct Answer: B. Inside-out
Rationale: Useful for applying second messengers.
8. The selectivity filter of K+ channels contains the signature sequence:
A. DEKA
B. EEEE
C. TVGYG
D. GGGG
Correct Answer: C. TVGYG
Rationale: Carbonyl oxygens mimic K+ hydration shell.
9. [Ca2+]out = 2 mM and [Ca2+]in = 0.0001 mM at 37 C. ECa is about:
A. +264 mV
B. +132 mV
C. -132 mV
D. +61 mV
Correct Answer: B. +132 mV
Rationale: 30.75 x log10(20,000) = 132 mV.
10. Only a tiny number of ions need to cross the membrane to set the resting potential because:
A. Ions are very large
B. Ion channels are rare
C. The pump stores charge
D. The membrane capacitance is small relative to cell volume
Correct Answer: D. The membrane capacitance is small relative to cell volume
Rationale: Bulk concentrations barely change.
11. If the Na+/K+ pump is blocked with ouabain, the resting potential will:
A. Immediately collapse to 0 mV
B. Slowly depolarize as gradients run down
C. Hyperpolarize
D. Stay the same forever
Correct Answer: B. Slowly depolarize as gradients run down
Rationale: Gradients dissipate over minutes to hours.
12. [Cl-]out = 110 mM and [Cl-]in = 10 mM at 37 C. ECl is about:
A. +64 mV
B. -89 mV
C. 0 mV
D. -64 mV
Correct Answer: D. -64 mV
Rationale: For z = -1, E = -61.5 x log10(110/10).
