,1. Which of the following is the primary functional unit of the nervous system?
A) Glial cell
B) Neuron
C) Axon
D) Dendrite
Correct Answer: Neuron
Rationale: The neuron is the fundamental excitable cell responsible for transmitting electrical
and chemical signals throughout the nervous system. Glial cells provide support and protection
for neurons but do not generate or conduct impulses. Axons and dendrites are specialized
processes of the neuron itself .
2. The part of the neuron that receives incoming signals from other cells is the:
A) Axon
B) Axon terminal
C) Dendrite
D) Myelin sheath
Correct Answer: Dendrite
Rationale: Dendrites are highly branched extensions of the neuron that act as the primary
receivers of synaptic input from other neurons. The axon conducts impulses away from the cell
body, while the myelin sheath is an insulating layer that speeds conduction .
3. Which ion is primarily responsible for the depolarization phase of an action potential?
A) Potassium (K⁺)
,B) Sodium (Na⁺)
C) Calcium (Ca²⁺)
D) Chloride (Cl⁻)
Correct Answer: Sodium (Na⁺)
Rationale: During depolarization, voltage-gated sodium channels open, allowing a rapid influx of
Na⁺ ions into the neuron, making the inside of the membrane positive relative to the outside.
Potassium efflux is responsible for repolarization. Calcium plays a role in neurotransmitter
release, and chloride contributes to hyperpolarization .
4. The period during which a neuron cannot generate another action potential regardless of
stimulus strength is the:
A) Relative refractory period
B) Absolute refractory period
C) Resting membrane potential
D) Graded potential
Correct Answer: Absolute refractory period
Rationale: During the absolute refractory period, voltage-gated sodium channels are inactivated
and cannot reopen, making it impossible to initiate another action potential. This period
ensures unidirectional propagation and limits the frequency of action potentials. The relative
refractory period allows generation with a stronger-than-normal stimulus .
5. What is the primary function of the myelin sheath?
A) To produce neurotransmitters
B) To increase the speed of impulse conduction
, C) To generate action potentials
D) To provide nutrients to the neuron
Correct Answer: To increase the speed of impulse conduction
Rationale: The myelin sheath is a fatty insulating layer that wraps around axons, allowing for
saltatory conduction where the action potential "jumps" between Nodes of Ranvier. This
dramatically increases conduction velocity compared to unmyelinated fibers. Myelin is
produced by oligodendrocytes in the CNS and Schwann cells in the PNS .
6. Which neuroglial cell is responsible for forming myelin sheaths in the central nervous system?
A) Schwann cell
B) Astrocyte
C) Oligodendrocyte
D) Microglia
Correct Answer: Oligodendrocyte
Rationale: Oligodendrocytes are the myelinating cells of the central nervous system, with each
cell capable of myelinating multiple axons. Schwann cells perform the same function in the
peripheral nervous system but myelinate only a single axon segment. Astrocytes provide
structural support and regulate the blood-brain barrier .
7. The gap between two communicating neurons where neurotransmitters are released is called
the:
A) Myelin gap
B) Synaptic cleft
C) Node of Ranvier
A) Glial cell
B) Neuron
C) Axon
D) Dendrite
Correct Answer: Neuron
Rationale: The neuron is the fundamental excitable cell responsible for transmitting electrical
and chemical signals throughout the nervous system. Glial cells provide support and protection
for neurons but do not generate or conduct impulses. Axons and dendrites are specialized
processes of the neuron itself .
2. The part of the neuron that receives incoming signals from other cells is the:
A) Axon
B) Axon terminal
C) Dendrite
D) Myelin sheath
Correct Answer: Dendrite
Rationale: Dendrites are highly branched extensions of the neuron that act as the primary
receivers of synaptic input from other neurons. The axon conducts impulses away from the cell
body, while the myelin sheath is an insulating layer that speeds conduction .
3. Which ion is primarily responsible for the depolarization phase of an action potential?
A) Potassium (K⁺)
,B) Sodium (Na⁺)
C) Calcium (Ca²⁺)
D) Chloride (Cl⁻)
Correct Answer: Sodium (Na⁺)
Rationale: During depolarization, voltage-gated sodium channels open, allowing a rapid influx of
Na⁺ ions into the neuron, making the inside of the membrane positive relative to the outside.
Potassium efflux is responsible for repolarization. Calcium plays a role in neurotransmitter
release, and chloride contributes to hyperpolarization .
4. The period during which a neuron cannot generate another action potential regardless of
stimulus strength is the:
A) Relative refractory period
B) Absolute refractory period
C) Resting membrane potential
D) Graded potential
Correct Answer: Absolute refractory period
Rationale: During the absolute refractory period, voltage-gated sodium channels are inactivated
and cannot reopen, making it impossible to initiate another action potential. This period
ensures unidirectional propagation and limits the frequency of action potentials. The relative
refractory period allows generation with a stronger-than-normal stimulus .
5. What is the primary function of the myelin sheath?
A) To produce neurotransmitters
B) To increase the speed of impulse conduction
, C) To generate action potentials
D) To provide nutrients to the neuron
Correct Answer: To increase the speed of impulse conduction
Rationale: The myelin sheath is a fatty insulating layer that wraps around axons, allowing for
saltatory conduction where the action potential "jumps" between Nodes of Ranvier. This
dramatically increases conduction velocity compared to unmyelinated fibers. Myelin is
produced by oligodendrocytes in the CNS and Schwann cells in the PNS .
6. Which neuroglial cell is responsible for forming myelin sheaths in the central nervous system?
A) Schwann cell
B) Astrocyte
C) Oligodendrocyte
D) Microglia
Correct Answer: Oligodendrocyte
Rationale: Oligodendrocytes are the myelinating cells of the central nervous system, with each
cell capable of myelinating multiple axons. Schwann cells perform the same function in the
peripheral nervous system but myelinate only a single axon segment. Astrocytes provide
structural support and regulate the blood-brain barrier .
7. The gap between two communicating neurons where neurotransmitters are released is called
the:
A) Myelin gap
B) Synaptic cleft
C) Node of Ranvier
