UTSC NROB61 Neurophysiology: Final Exam (Comprehensive)
- Questions with Correct Answers
50 questions
1. Mutations that disrupt channel function and cause disease are called:
A. Synaptopathies only
B. Channelopathies
C. Myopathies only
D. Gliopathies
Correct Answer: B. Channelopathies
Rationale: E.g., some epilepsies and long QT syndrome.
2. Why do K+ channels exclude the smaller Na+ ion?
A. Na+ is larger than K+
B. Na+ has a negative charge
C. Na+ binds ATP
D. Na+ cannot be stabilized by the filter's carbonyl oxygens after losing its water shell
Correct Answer: D. Na+ cannot be stabilized by the filter's carbonyl oxygens after losing its
water shell
Rationale: The energetic cost of dehydration is not compensated.
3. The resting membrane potential is closest to EK because:
A. The resting membrane is much more permeable to K+ than to Na+
B. K+ concentration is higher outside
C. The pump moves only K+
D. Na+ channels are always open
Correct Answer: A. The resting membrane is much more permeable to K+ than to Na+
Rationale: GHK weights permeability.
4. [Na+]out = 145 mM and [Na+]in = 15 mM at 37 C. ENa is about:
A. -61 mV
B. +89 mV
C. +61 mV
D. +30 mV
Correct Answer: C. +61 mV
Rationale: 61.5 x log10(145/15) = +60.6 mV.
5. Removal of Na+ channel inactivation (de-inactivation) requires:
A. Further depolarization
B. TTX
C. High extracellular K+
D. Repolarization of the membrane
Correct Answer: D. Repolarization of the membrane
Rationale: The h gate recovers at negative potentials.
6. Tetrodotoxin (TTX) blocks action potentials by:
A. Blocking K+ channels
B. Blocking the pump
C. Activating Cl- channels
D. Blocking voltage-gated Na+ channels
Correct Answer: D. Blocking voltage-gated Na+ channels
Rationale: From pufferfish.
, 7. In the equivalent circuit of a neuron, the lipid bilayer acts as a:
A. Resistor
B. Capacitor
C. Battery
D. Diode
Correct Answer: B. Capacitor
Rationale: It separates and stores charge.
8. In the equivalent circuit, ion channels act as:
A. Resistors (conductances)
B. Capacitors
C. Inductors
D. Switches with no resistance
Correct Answer: A. Resistors (conductances)
Rationale: They allow current to flow.
9. Lambda is proportional to:
A. sqrt(rm / ri)
B. rm x ri
C. ri / rm
D. Cm x Rm
Correct Answer: A. sqrt(rm / ri)
Rationale: Higher membrane resistance and lower axial resistance increase lambda.
10. Different peaks in a compound action potential reflect:
A. Fiber groups with different conduction velocities
B. Different neurotransmitters
C. Different ions
D. Noise
Correct Answer: A. Fiber groups with different conduction velocities
Rationale: A-alpha, A-delta, C fibers.
11. Temporal summation occurs when:
A. Inputs arrive at different sites
B. Only inhibitory inputs fire
C. The axon fires backward
D. Successive inputs at the same synapse arrive before earlier ones decay
Correct Answer: D. Successive inputs at the same synapse arrive before earlier ones decay
Rationale: Depends on the time constant.
12. Coincident EPSPs that together exceed threshold demonstrate that neurons act as:
A. Passive cables only
B. Batteries
C. Pumps
D. Coincidence detectors
Correct Answer: D. Coincidence detectors
Rationale: Timing matters.
- Questions with Correct Answers
50 questions
1. Mutations that disrupt channel function and cause disease are called:
A. Synaptopathies only
B. Channelopathies
C. Myopathies only
D. Gliopathies
Correct Answer: B. Channelopathies
Rationale: E.g., some epilepsies and long QT syndrome.
2. Why do K+ channels exclude the smaller Na+ ion?
A. Na+ is larger than K+
B. Na+ has a negative charge
C. Na+ binds ATP
D. Na+ cannot be stabilized by the filter's carbonyl oxygens after losing its water shell
Correct Answer: D. Na+ cannot be stabilized by the filter's carbonyl oxygens after losing its
water shell
Rationale: The energetic cost of dehydration is not compensated.
3. The resting membrane potential is closest to EK because:
A. The resting membrane is much more permeable to K+ than to Na+
B. K+ concentration is higher outside
C. The pump moves only K+
D. Na+ channels are always open
Correct Answer: A. The resting membrane is much more permeable to K+ than to Na+
Rationale: GHK weights permeability.
4. [Na+]out = 145 mM and [Na+]in = 15 mM at 37 C. ENa is about:
A. -61 mV
B. +89 mV
C. +61 mV
D. +30 mV
Correct Answer: C. +61 mV
Rationale: 61.5 x log10(145/15) = +60.6 mV.
5. Removal of Na+ channel inactivation (de-inactivation) requires:
A. Further depolarization
B. TTX
C. High extracellular K+
D. Repolarization of the membrane
Correct Answer: D. Repolarization of the membrane
Rationale: The h gate recovers at negative potentials.
6. Tetrodotoxin (TTX) blocks action potentials by:
A. Blocking K+ channels
B. Blocking the pump
C. Activating Cl- channels
D. Blocking voltage-gated Na+ channels
Correct Answer: D. Blocking voltage-gated Na+ channels
Rationale: From pufferfish.
, 7. In the equivalent circuit of a neuron, the lipid bilayer acts as a:
A. Resistor
B. Capacitor
C. Battery
D. Diode
Correct Answer: B. Capacitor
Rationale: It separates and stores charge.
8. In the equivalent circuit, ion channels act as:
A. Resistors (conductances)
B. Capacitors
C. Inductors
D. Switches with no resistance
Correct Answer: A. Resistors (conductances)
Rationale: They allow current to flow.
9. Lambda is proportional to:
A. sqrt(rm / ri)
B. rm x ri
C. ri / rm
D. Cm x Rm
Correct Answer: A. sqrt(rm / ri)
Rationale: Higher membrane resistance and lower axial resistance increase lambda.
10. Different peaks in a compound action potential reflect:
A. Fiber groups with different conduction velocities
B. Different neurotransmitters
C. Different ions
D. Noise
Correct Answer: A. Fiber groups with different conduction velocities
Rationale: A-alpha, A-delta, C fibers.
11. Temporal summation occurs when:
A. Inputs arrive at different sites
B. Only inhibitory inputs fire
C. The axon fires backward
D. Successive inputs at the same synapse arrive before earlier ones decay
Correct Answer: D. Successive inputs at the same synapse arrive before earlier ones decay
Rationale: Depends on the time constant.
12. Coincident EPSPs that together exceed threshold demonstrate that neurons act as:
A. Passive cables only
B. Batteries
C. Pumps
D. Coincidence detectors
Correct Answer: D. Coincidence detectors
Rationale: Timing matters.
