NU 545 Advanced Pathophysiology Unit 2 Exam
2026/2027: Nervous System & Neuro-
Pathophysiology Study Guide with 250+ Verified
Questions, Correct Answers, and Detailed
Rationales – Latest Update, Just Released, Graded
A+
Chapter 1: Cellular and Molecular Neuroscience
Questions 1–25
1. Which component of the neuron is primarily responsible for the initiation of
the action potential?
A. Dendrite
B. Axon hillock
C. Node of Ranvier
D. Axon terminal
Correct Answer: B. Axon hillock
Rationale: The axon hillock is the region where the axon emerges from
the cell body (soma) and has the highest density of voltage-gated sodium
channels. It serves as the "trigger zone" where the summation of excitatory and
inhibitory postsynaptic potentials (EPSPs and IPSPs) is evaluated. If the summed
depolarization reaches threshold (approximately −55 mV), an action potential is
initiated and propagated down the axon. Dendrites primarily receive synaptic
inputs and conduct graded potentials toward the soma. Nodes of Ranvier are gaps
in the myelin sheath that facilitate saltatory conduction but do not initiate action
potentials. Axon terminals are responsible for neurotransmitter release, not
initiation.
,2. The resting membrane potential of a typical neuron is approximately −70 mV.
Which ion contributes most to the establishment of this resting potential?
A. Sodium (Na⁺)
B. Calcium (Ca²⁺)
C. Potassium (K⁺)
D. Chloride (Cl⁻)
Correct Answer: C. Potassium (K⁺)
Rationale: The resting membrane potential is primarily determined by the
concentration gradient of K⁺ across the membrane and the relative permeability
of the membrane to K⁺ at rest. The Na⁺/K⁺-ATPase pump maintains a high
intracellular K⁺ concentration and a high extracellular Na⁺ concentration. Because
the resting membrane is far more permeable to K⁺ than to Na⁺ (due to leak
channels), the membrane potential sits close to the equilibrium potential for K⁺
(approximately −90 mV), though it is slightly depolarized to −70 mV due to a small
contribution from Na⁺ leak. Na⁺, Ca²⁺, and Cl⁻ contribute to the resting potential
but are not the primary determinants.
3. Select all that apply. Which of the following are characteristics of an action
potential?
A. It is a graded response proportional to stimulus strength.
B. It follows the all-or-none principle.
C. It involves the opening of voltage-gated sodium channels.
D. It can summate temporally and spatially.
E. It is propagated without decrement along the axon.
Correct Answer: B, C, E
Rationale: Action potentials follow the all-or-none principle (B), meaning
that once threshold is reached, the amplitude and duration are constant
regardless of stimulus strength. They involve the rapid opening of voltage-gated
Na⁺ channels (C), leading to depolarization, followed by inactivation and opening
of voltage-gated K⁺ channels for repolarization. Action potentials propagate
without decrement (E) because they are actively regenerated at each point along
,the axon membrane. Graded responses (A) and summation (D) are characteristics
of postsynaptic potentials (EPSPs and IPSPs), not action potentials.
4. Which type of glial cell is primarily responsible for myelination in the central
nervous system?
A. Astrocyte
B. Oligodendrocyte
C. Schwann cell
D. Microglia
Correct Answer: B. Oligodendrocyte
Rationale: Oligodendrocytes are the myelinating cells of the central
nervous system (CNS). A single oligodendrocyte can myelinate multiple axon
segments. Schwann cells myelinate axons in the peripheral nervous system (PNS),
typically one segment per cell. Astrocytes provide metabolic support, regulate the
extracellular environment, contribute to the blood-brain barrier, and participate
in synaptic transmission. Microglia are the resident immune cells of the CNS and
mediate inflammatory responses.
5. A patient presents with a demyelinating lesion in the peripheral nervous
system. Which cell type is most likely affected?
A. Oligodendrocyte
B. Astrocyte
C. Schwann cell
D. Ependymal cell
Correct Answer: C. Schwann cell
Rationale: Schwann cells are the myelinating cells of the peripheral
nervous system (PNS). Demyelinating conditions affecting the PNS, such as
Guillain-Barré syndrome, involve damage to Schwann cells or their myelin
sheaths. Oligodendrocytes myelinate CNS axons; their damage is seen in multiple
, sclerosis and other CNS demyelinating diseases. Astrocytes and ependymal cells
are CNS glia and do not myelinate peripheral nerves.
6. Which of the following best describes the role of the Na⁺/K⁺-ATPase pump in
neuronal function?
A. It generates the action potential.
B. It maintains the resting membrane potential by transporting 3 Na⁺ out and 2 K⁺
in.
C. It transports 2 Na⁺ out and 3 K⁺ in, contributing to hyperpolarization.
D. It is only active during the absolute refractory period.
Correct Answer: B. It maintains the resting membrane potential by
transporting 3 Na⁺ out and 2 K⁺ in.
Rationale: The Na⁺/K⁺-ATPase pump uses ATP to transport three Na⁺ ions
out of the cell and two K⁺ ions into the cell, against their respective concentration
gradients. This electrogenic pump contributes to the negative resting membrane
potential and maintains the ionic gradients necessary for excitability. It operates
continuously, not only during the refractory period, and does not generate the
action potential itself (though it restores ionic gradients after firing).
7. Select all that apply. Which of the following are functions of astrocytes?
A. Formation of the blood-brain barrier
B. Myelination of CNS axons
C. Regulation of extracellular potassium concentration
D. Phagocytosis of pathogens
E. Provision of metabolic substrates to neurons
Correct Answer: A, C, E
Rationale: Astrocytes contribute to the blood-brain barrier (A) by inducing
tight junction formation in endothelial cells and ensheathing capillaries. They
regulate extracellular K⁺ concentration (C) by buffering excess K⁺ released during
neuronal activity, which is critical for maintaining excitability. They also provide
2026/2027: Nervous System & Neuro-
Pathophysiology Study Guide with 250+ Verified
Questions, Correct Answers, and Detailed
Rationales – Latest Update, Just Released, Graded
A+
Chapter 1: Cellular and Molecular Neuroscience
Questions 1–25
1. Which component of the neuron is primarily responsible for the initiation of
the action potential?
A. Dendrite
B. Axon hillock
C. Node of Ranvier
D. Axon terminal
Correct Answer: B. Axon hillock
Rationale: The axon hillock is the region where the axon emerges from
the cell body (soma) and has the highest density of voltage-gated sodium
channels. It serves as the "trigger zone" where the summation of excitatory and
inhibitory postsynaptic potentials (EPSPs and IPSPs) is evaluated. If the summed
depolarization reaches threshold (approximately −55 mV), an action potential is
initiated and propagated down the axon. Dendrites primarily receive synaptic
inputs and conduct graded potentials toward the soma. Nodes of Ranvier are gaps
in the myelin sheath that facilitate saltatory conduction but do not initiate action
potentials. Axon terminals are responsible for neurotransmitter release, not
initiation.
,2. The resting membrane potential of a typical neuron is approximately −70 mV.
Which ion contributes most to the establishment of this resting potential?
A. Sodium (Na⁺)
B. Calcium (Ca²⁺)
C. Potassium (K⁺)
D. Chloride (Cl⁻)
Correct Answer: C. Potassium (K⁺)
Rationale: The resting membrane potential is primarily determined by the
concentration gradient of K⁺ across the membrane and the relative permeability
of the membrane to K⁺ at rest. The Na⁺/K⁺-ATPase pump maintains a high
intracellular K⁺ concentration and a high extracellular Na⁺ concentration. Because
the resting membrane is far more permeable to K⁺ than to Na⁺ (due to leak
channels), the membrane potential sits close to the equilibrium potential for K⁺
(approximately −90 mV), though it is slightly depolarized to −70 mV due to a small
contribution from Na⁺ leak. Na⁺, Ca²⁺, and Cl⁻ contribute to the resting potential
but are not the primary determinants.
3. Select all that apply. Which of the following are characteristics of an action
potential?
A. It is a graded response proportional to stimulus strength.
B. It follows the all-or-none principle.
C. It involves the opening of voltage-gated sodium channels.
D. It can summate temporally and spatially.
E. It is propagated without decrement along the axon.
Correct Answer: B, C, E
Rationale: Action potentials follow the all-or-none principle (B), meaning
that once threshold is reached, the amplitude and duration are constant
regardless of stimulus strength. They involve the rapid opening of voltage-gated
Na⁺ channels (C), leading to depolarization, followed by inactivation and opening
of voltage-gated K⁺ channels for repolarization. Action potentials propagate
without decrement (E) because they are actively regenerated at each point along
,the axon membrane. Graded responses (A) and summation (D) are characteristics
of postsynaptic potentials (EPSPs and IPSPs), not action potentials.
4. Which type of glial cell is primarily responsible for myelination in the central
nervous system?
A. Astrocyte
B. Oligodendrocyte
C. Schwann cell
D. Microglia
Correct Answer: B. Oligodendrocyte
Rationale: Oligodendrocytes are the myelinating cells of the central
nervous system (CNS). A single oligodendrocyte can myelinate multiple axon
segments. Schwann cells myelinate axons in the peripheral nervous system (PNS),
typically one segment per cell. Astrocytes provide metabolic support, regulate the
extracellular environment, contribute to the blood-brain barrier, and participate
in synaptic transmission. Microglia are the resident immune cells of the CNS and
mediate inflammatory responses.
5. A patient presents with a demyelinating lesion in the peripheral nervous
system. Which cell type is most likely affected?
A. Oligodendrocyte
B. Astrocyte
C. Schwann cell
D. Ependymal cell
Correct Answer: C. Schwann cell
Rationale: Schwann cells are the myelinating cells of the peripheral
nervous system (PNS). Demyelinating conditions affecting the PNS, such as
Guillain-Barré syndrome, involve damage to Schwann cells or their myelin
sheaths. Oligodendrocytes myelinate CNS axons; their damage is seen in multiple
, sclerosis and other CNS demyelinating diseases. Astrocytes and ependymal cells
are CNS glia and do not myelinate peripheral nerves.
6. Which of the following best describes the role of the Na⁺/K⁺-ATPase pump in
neuronal function?
A. It generates the action potential.
B. It maintains the resting membrane potential by transporting 3 Na⁺ out and 2 K⁺
in.
C. It transports 2 Na⁺ out and 3 K⁺ in, contributing to hyperpolarization.
D. It is only active during the absolute refractory period.
Correct Answer: B. It maintains the resting membrane potential by
transporting 3 Na⁺ out and 2 K⁺ in.
Rationale: The Na⁺/K⁺-ATPase pump uses ATP to transport three Na⁺ ions
out of the cell and two K⁺ ions into the cell, against their respective concentration
gradients. This electrogenic pump contributes to the negative resting membrane
potential and maintains the ionic gradients necessary for excitability. It operates
continuously, not only during the refractory period, and does not generate the
action potential itself (though it restores ionic gradients after firing).
7. Select all that apply. Which of the following are functions of astrocytes?
A. Formation of the blood-brain barrier
B. Myelination of CNS axons
C. Regulation of extracellular potassium concentration
D. Phagocytosis of pathogens
E. Provision of metabolic substrates to neurons
Correct Answer: A, C, E
Rationale: Astrocytes contribute to the blood-brain barrier (A) by inducing
tight junction formation in endothelial cells and ensheathing capillaries. They
regulate extracellular K⁺ concentration (C) by buffering excess K⁺ released during
neuronal activity, which is critical for maintaining excitability. They also provide
