NSCI 225 QUIZZES | QUESTIONS AND ANSWERS |
LATEST UPDATE | WITH COMPLETE SOLUTION
course of perceptual experience
Environmental stimulus --> stimulus on receptor --> transduction --> processing --
> perception --> recognition --> action
NSCI 225: Foundational Neuroscience Quiz (Sample Format)
Question 1: The Action Potential - Beyond the Graph
During a laboratory experiment, you place electrodes inside and outside a squid
giant axon. You measure the resting membrane potential at -70 mV. Upon
sufficient stimulation, the membrane potential rapidly rises to +40 mV and then
falls, overshooting slightly below -70 mV before returning to baseline.
Which of the following manipulations would MOST SPECIFICALLY prevent
the repolarization phase of the action potential, and why?
a) Increasing the extracellular concentration of potassium (K⁺) ions.
b) Applying a toxin that blocks voltage-gated sodium (Na⁺) channels.
c) Applying tetraethylammonium (TEA), a blocker of voltage-gated potassium (K⁺)
channels.
d) Decreasing the extracellular concentration of sodium (Na⁺) ions.
Correct Answer: c
Rationale: This tests precise mechanistic knowledge. The repolarization phase is
driven primarily by the outward flow of K⁺ ions through voltage-gated potassium
channels. Blocking these channels with TEA (c) would prevent this outward
,current, halting repolarization. (a) Altering extracellular K⁺ affects the resting
potential and the equilibrium potential for K⁺, making it harder to repolarize to
the correct level, but does not directly block the repolarization mechanism. (b)
Blocking Na⁺ channels prevents depolarization/initiation altogether. (d) Reducing
extracellular Na⁺ lowers the equilibrium potential for Na⁺, decreasing the peak of
the action potential, but does not specifically block repolarization.
Question 2: Synaptic Integration Logic
A postsynaptic neuron has a resting membrane potential of -65 mV. The threshold
for triggering an action potential at its axon initial segment is -55 mV. It receives
nearly simultaneous input from three synapses:
• Synapse A (Excitatory): Produces an EPSP of +5 mV.
• Synapse B (Excitatory): Produces an EPSP of +8 mV.
• Synapse C (Inhibitory): Produces an IPSP of -4 mV.
Assuming simple linear summation, what is the resulting membrane potential at
the integration zone, and will an action potential be initiated?
a) -56 mV; No
b) -56 mV; Yes
c) -72 mV; No
d) -52 mV; Yes
Correct Answer: a
Rationale: This tests basic arithmetic of synaptic summation. Start at -65 mV. Add
the changes: +5 (A) +8 (B) -4 (C) = +9 mV net change. -65 mV + 9 mV = -56 mV.
This value (-56 mV) is more negative (hyperpolarized relative to) the threshold of
-55 mV. Therefore, it does not reach threshold. Key Distraction: Option (d) results
from an arithmetic error (-65+17 = -48, not -52) or misadding the potentials.
Question 3: Neurotransmitter Systems & Pharmacology
Parkinson's disease is characterized by the degeneration of dopaminergic neurons
in the substantia nigra pars compacta. The standard pharmacological treatment is
L-DOPA, a precursor to dopamine.
Why is L-DOPA administered instead of direct dopamine, and what is a major
long-term side effect of this treatment?
,a) Dopamine cannot be synthesized in the brain; L-DOPA can. A major side effect
is cardiac arrhythmia due to peripheral dopamine effects.
b) Dopamine cannot cross the blood-brain barrier (BBB); L-DOPA can via amino
acid transporters. A major side effect is dyskinesias (involuntary movements) due
to fluctuating dopamine levels and receptor sensitization.
c) L-DOPA has a greater affinity for dopamine receptors than dopamine itself. A
major side effect is psychosis due to overstimulation of mesolimbic pathways.
d) Direct dopamine would be broken down too quickly in the bloodstream. A
major side effect is hypertensive crisis due to interaction with certain foods.
Correct Answer: b
Rationale: This integrates anatomy, physiology, and clinical pharmacology.
The blood-brain barrier is the key concept. Dopamine is a polar molecule that
cannot diffuse across the BBB. L-DOPA uses active transport. The long-term
motor side effect of pulsatile dopamine replacement is debilitating dyskinesias, a
core challenge in Parkinson's management. (a) is incorrect because
dopamine is synthesized in the brain (from L-DOPA). (c) is incorrect; L-DOPA has
no receptor affinity itself—it's a precursor. (d) describes a concern with
monoamine oxidase inhibitors (MAOIs), not the primary mechanism or most
common long-term motor side effect of L-DOPA.
Question 4: Brain Anatomy & Function Correlation
A patient presents with the following symptoms: severe short-term memory
deficits, inability to form new conscious memories (anterograde amnesia), and
mild retrograde amnesia for events preceding the injury. MRI shows bilateral
damage.
Which brain structure is MOST likely damaged?
a) Prefrontal cortex
b) Cerebellum
c) Hippocampus
d) Amygdala
Correct Answer: c
Rationale: This tests classic clinical-anatomical correlation. The hippocampus and
surrounding medial temporal lobe structures are essential for
the consolidation of new declarative (explicit) memories. Bilateral hippocampal
, damage (as in the famous case of H.M.) leads to profound anterograde
amnesia and temporally graded retrograde amnesia. (a) Prefrontal cortex
damage affects executive function, working memory, and personality, not pure
memory consolidation. (b) Cerebellum damage affects motor coordination and
procedural learning. (d) Amygdala damage affects emotional processing and fear
conditioning.
Question 5: The Visual Pathway - From Eye to Cortex
Light hits the nasal retina of the left eye. The signal is transmitted via retinal
ganglion cells.
Through which structure and to which primary visual cortex hemisphere will this
information ultimately be processed for conscious perception?
a) Left optic tract; Right primary visual cortex
b) Left optic tract; Left primary visual cortex
c) Optic chiasm (crossing); Right primary visual cortex
d) Optic chiasm (crossing); Left primary visual cortex
Correct Answer: c
Rationale: This tests knowledge of the retinofugal projection. A key
rule: Information from the nasal retina crosses at the optic chiasm. Light from
the left visual field (which hits the nasal retina of the left eye and the temporal
retina of the right eye) is processed by the right hemisphere. Pathway: Left nasal
retina → Left optic nerve → Crosses at optic chiasm → Right optic tract → Right
lateral geniculate nucleus (LGN) → Right optic radiations → Right primary visual
cortex (V1). (a) and (b) incorrectly route the crossed information into the left
optic tract. (d) correctly identifies crossing but sends it to the incorrect
hemisphere.
1. What is the dark adaptation curve?
Answer:
The dark adaptation curve shows how visual sensitivity improves over time in
darkness as photoreceptors adapt.
LATEST UPDATE | WITH COMPLETE SOLUTION
course of perceptual experience
Environmental stimulus --> stimulus on receptor --> transduction --> processing --
> perception --> recognition --> action
NSCI 225: Foundational Neuroscience Quiz (Sample Format)
Question 1: The Action Potential - Beyond the Graph
During a laboratory experiment, you place electrodes inside and outside a squid
giant axon. You measure the resting membrane potential at -70 mV. Upon
sufficient stimulation, the membrane potential rapidly rises to +40 mV and then
falls, overshooting slightly below -70 mV before returning to baseline.
Which of the following manipulations would MOST SPECIFICALLY prevent
the repolarization phase of the action potential, and why?
a) Increasing the extracellular concentration of potassium (K⁺) ions.
b) Applying a toxin that blocks voltage-gated sodium (Na⁺) channels.
c) Applying tetraethylammonium (TEA), a blocker of voltage-gated potassium (K⁺)
channels.
d) Decreasing the extracellular concentration of sodium (Na⁺) ions.
Correct Answer: c
Rationale: This tests precise mechanistic knowledge. The repolarization phase is
driven primarily by the outward flow of K⁺ ions through voltage-gated potassium
channels. Blocking these channels with TEA (c) would prevent this outward
,current, halting repolarization. (a) Altering extracellular K⁺ affects the resting
potential and the equilibrium potential for K⁺, making it harder to repolarize to
the correct level, but does not directly block the repolarization mechanism. (b)
Blocking Na⁺ channels prevents depolarization/initiation altogether. (d) Reducing
extracellular Na⁺ lowers the equilibrium potential for Na⁺, decreasing the peak of
the action potential, but does not specifically block repolarization.
Question 2: Synaptic Integration Logic
A postsynaptic neuron has a resting membrane potential of -65 mV. The threshold
for triggering an action potential at its axon initial segment is -55 mV. It receives
nearly simultaneous input from three synapses:
• Synapse A (Excitatory): Produces an EPSP of +5 mV.
• Synapse B (Excitatory): Produces an EPSP of +8 mV.
• Synapse C (Inhibitory): Produces an IPSP of -4 mV.
Assuming simple linear summation, what is the resulting membrane potential at
the integration zone, and will an action potential be initiated?
a) -56 mV; No
b) -56 mV; Yes
c) -72 mV; No
d) -52 mV; Yes
Correct Answer: a
Rationale: This tests basic arithmetic of synaptic summation. Start at -65 mV. Add
the changes: +5 (A) +8 (B) -4 (C) = +9 mV net change. -65 mV + 9 mV = -56 mV.
This value (-56 mV) is more negative (hyperpolarized relative to) the threshold of
-55 mV. Therefore, it does not reach threshold. Key Distraction: Option (d) results
from an arithmetic error (-65+17 = -48, not -52) or misadding the potentials.
Question 3: Neurotransmitter Systems & Pharmacology
Parkinson's disease is characterized by the degeneration of dopaminergic neurons
in the substantia nigra pars compacta. The standard pharmacological treatment is
L-DOPA, a precursor to dopamine.
Why is L-DOPA administered instead of direct dopamine, and what is a major
long-term side effect of this treatment?
,a) Dopamine cannot be synthesized in the brain; L-DOPA can. A major side effect
is cardiac arrhythmia due to peripheral dopamine effects.
b) Dopamine cannot cross the blood-brain barrier (BBB); L-DOPA can via amino
acid transporters. A major side effect is dyskinesias (involuntary movements) due
to fluctuating dopamine levels and receptor sensitization.
c) L-DOPA has a greater affinity for dopamine receptors than dopamine itself. A
major side effect is psychosis due to overstimulation of mesolimbic pathways.
d) Direct dopamine would be broken down too quickly in the bloodstream. A
major side effect is hypertensive crisis due to interaction with certain foods.
Correct Answer: b
Rationale: This integrates anatomy, physiology, and clinical pharmacology.
The blood-brain barrier is the key concept. Dopamine is a polar molecule that
cannot diffuse across the BBB. L-DOPA uses active transport. The long-term
motor side effect of pulsatile dopamine replacement is debilitating dyskinesias, a
core challenge in Parkinson's management. (a) is incorrect because
dopamine is synthesized in the brain (from L-DOPA). (c) is incorrect; L-DOPA has
no receptor affinity itself—it's a precursor. (d) describes a concern with
monoamine oxidase inhibitors (MAOIs), not the primary mechanism or most
common long-term motor side effect of L-DOPA.
Question 4: Brain Anatomy & Function Correlation
A patient presents with the following symptoms: severe short-term memory
deficits, inability to form new conscious memories (anterograde amnesia), and
mild retrograde amnesia for events preceding the injury. MRI shows bilateral
damage.
Which brain structure is MOST likely damaged?
a) Prefrontal cortex
b) Cerebellum
c) Hippocampus
d) Amygdala
Correct Answer: c
Rationale: This tests classic clinical-anatomical correlation. The hippocampus and
surrounding medial temporal lobe structures are essential for
the consolidation of new declarative (explicit) memories. Bilateral hippocampal
, damage (as in the famous case of H.M.) leads to profound anterograde
amnesia and temporally graded retrograde amnesia. (a) Prefrontal cortex
damage affects executive function, working memory, and personality, not pure
memory consolidation. (b) Cerebellum damage affects motor coordination and
procedural learning. (d) Amygdala damage affects emotional processing and fear
conditioning.
Question 5: The Visual Pathway - From Eye to Cortex
Light hits the nasal retina of the left eye. The signal is transmitted via retinal
ganglion cells.
Through which structure and to which primary visual cortex hemisphere will this
information ultimately be processed for conscious perception?
a) Left optic tract; Right primary visual cortex
b) Left optic tract; Left primary visual cortex
c) Optic chiasm (crossing); Right primary visual cortex
d) Optic chiasm (crossing); Left primary visual cortex
Correct Answer: c
Rationale: This tests knowledge of the retinofugal projection. A key
rule: Information from the nasal retina crosses at the optic chiasm. Light from
the left visual field (which hits the nasal retina of the left eye and the temporal
retina of the right eye) is processed by the right hemisphere. Pathway: Left nasal
retina → Left optic nerve → Crosses at optic chiasm → Right optic tract → Right
lateral geniculate nucleus (LGN) → Right optic radiations → Right primary visual
cortex (V1). (a) and (b) incorrectly route the crossed information into the left
optic tract. (d) correctly identifies crossing but sends it to the incorrect
hemisphere.
1. What is the dark adaptation curve?
Answer:
The dark adaptation curve shows how visual sensitivity improves over time in
darkness as photoreceptors adapt.
