UTSC NROB61 Neurophysiology: Practice Test 2 (Units 8-13) -
Questions with Correct Answers
50 questions
1. Neuromuscular junctions are reliable because:
A. Quantal content is high, giving a large safety factor
B. Release probability is near zero
C. They use electrical synapses
D. Only one vesicle is released
Correct Answer: A. Quantal content is high, giving a large safety factor
Rationale: The EPP exceeds threshold.
2. The immediate trigger for synaptic vesicle fusion is:
A. Na+ entry
B. K+ efflux
C. Cl- entry
D. Ca2+ entry through voltage-gated Ca2+ channels
Correct Answer: D. Ca2+ entry through voltage-gated Ca2+ channels
Rationale: Ca2+ binds synaptotagmin.
3. Under low-Ca2+ conditions, EPP amplitudes cluster at integer multiples of:
A. The AP amplitude
B. The resting potential
C. The mEPP amplitude
D. 1 mV exactly
Correct Answer: C. The mEPP amplitude
Rationale: This defines quantal release.
4. In low Ca2+, 100 stimuli produce 37 failures. Using Poisson statistics, quantal content m is
about:
A. 0.37
B. 2.7
C. 1
D. 37
Correct Answer: C. 1
Rationale: m = ln(100/37) = 0.99.
5. A key function of electrical synapses is:
A. Long-term memory storage only
B. Inhibition only
C. Synchronizing the activity of coupled neurons
D. Amplifying signals
Correct Answer: C. Synchronizing the activity of coupled neurons
Rationale: E.g., inferior olive.
6. Curare blocks neuromuscular transmission by:
A. Competitively blocking nicotinic ACh receptors
B. Blocking ACh release
C. Inhibiting acetylcholinesterase
D. Blocking Ca2+ channels
Correct Answer: A. Competitively blocking nicotinic ACh receptors
Rationale: Used historically in hunting.
, 7. Electrical synapses differ from chemical synapses because they:
A. Use neurotransmitters
B. Are always one-way
C. Pass current directly through gap junctions with almost no delay
D. Amplify signals
Correct Answer: C. Pass current directly through gap junctions with almost no delay
Rationale: Connexin channels.
8. Release probability is raised by increasing:
A. Extracellular Mg2+
B. TTX
C. Extracellular Ca2+
D. Cl- concentration
Correct Answer: C. Extracellular Ca2+
Rationale: Mg2+ competes with Ca2+.
9. Asynchronous release differs from synchronous release because it:
A. Occurs within 1 ms
B. Requires no Ca2+
C. Uses gap junctions
D. Continues for tens to hundreds of milliseconds after the AP
Correct Answer: D. Continues for tens to hundreds of milliseconds after the AP
Rationale: Different Ca2+ sensors.
10. Bicuculline blocks:
A. NMDA receptors
B. GABA-A receptors
C. Glycine receptors
D. Nicotinic receptors
Correct Answer: B. GABA-A receptors
Rationale: Used to induce disinhibition.
11. Strychnine poisoning causes convulsions because it blocks:
A. AMPA receptors
B. Na+ channels
C. Acetylcholinesterase
D. Glycine receptors
Correct Answer: D. Glycine receptors
Rationale: Loss of spinal inhibition.
12. A synaptic current reverses at -70 mV in a neuron with threshold -50 mV. The synapse is:
A. Excitatory
B. Neither
C. Inhibitory
D. Electrical
Correct Answer: C. Inhibitory
Rationale: It pulls Vm away from threshold.
Questions with Correct Answers
50 questions
1. Neuromuscular junctions are reliable because:
A. Quantal content is high, giving a large safety factor
B. Release probability is near zero
C. They use electrical synapses
D. Only one vesicle is released
Correct Answer: A. Quantal content is high, giving a large safety factor
Rationale: The EPP exceeds threshold.
2. The immediate trigger for synaptic vesicle fusion is:
A. Na+ entry
B. K+ efflux
C. Cl- entry
D. Ca2+ entry through voltage-gated Ca2+ channels
Correct Answer: D. Ca2+ entry through voltage-gated Ca2+ channels
Rationale: Ca2+ binds synaptotagmin.
3. Under low-Ca2+ conditions, EPP amplitudes cluster at integer multiples of:
A. The AP amplitude
B. The resting potential
C. The mEPP amplitude
D. 1 mV exactly
Correct Answer: C. The mEPP amplitude
Rationale: This defines quantal release.
4. In low Ca2+, 100 stimuli produce 37 failures. Using Poisson statistics, quantal content m is
about:
A. 0.37
B. 2.7
C. 1
D. 37
Correct Answer: C. 1
Rationale: m = ln(100/37) = 0.99.
5. A key function of electrical synapses is:
A. Long-term memory storage only
B. Inhibition only
C. Synchronizing the activity of coupled neurons
D. Amplifying signals
Correct Answer: C. Synchronizing the activity of coupled neurons
Rationale: E.g., inferior olive.
6. Curare blocks neuromuscular transmission by:
A. Competitively blocking nicotinic ACh receptors
B. Blocking ACh release
C. Inhibiting acetylcholinesterase
D. Blocking Ca2+ channels
Correct Answer: A. Competitively blocking nicotinic ACh receptors
Rationale: Used historically in hunting.
, 7. Electrical synapses differ from chemical synapses because they:
A. Use neurotransmitters
B. Are always one-way
C. Pass current directly through gap junctions with almost no delay
D. Amplify signals
Correct Answer: C. Pass current directly through gap junctions with almost no delay
Rationale: Connexin channels.
8. Release probability is raised by increasing:
A. Extracellular Mg2+
B. TTX
C. Extracellular Ca2+
D. Cl- concentration
Correct Answer: C. Extracellular Ca2+
Rationale: Mg2+ competes with Ca2+.
9. Asynchronous release differs from synchronous release because it:
A. Occurs within 1 ms
B. Requires no Ca2+
C. Uses gap junctions
D. Continues for tens to hundreds of milliseconds after the AP
Correct Answer: D. Continues for tens to hundreds of milliseconds after the AP
Rationale: Different Ca2+ sensors.
10. Bicuculline blocks:
A. NMDA receptors
B. GABA-A receptors
C. Glycine receptors
D. Nicotinic receptors
Correct Answer: B. GABA-A receptors
Rationale: Used to induce disinhibition.
11. Strychnine poisoning causes convulsions because it blocks:
A. AMPA receptors
B. Na+ channels
C. Acetylcholinesterase
D. Glycine receptors
Correct Answer: D. Glycine receptors
Rationale: Loss of spinal inhibition.
12. A synaptic current reverses at -70 mV in a neuron with threshold -50 mV. The synapse is:
A. Excitatory
B. Neither
C. Inhibitory
D. Electrical
Correct Answer: C. Inhibitory
Rationale: It pulls Vm away from threshold.
