NCERT-Based Explanation
The electrogenic Na⁺/K⁺ pump actively transports 3 Na⁺ ions out of the cell for every 2 K⁺ ions into the cell. This unequal ion movement, combined with differential membrane permeability, generates and maintains a resting membrane potential (electrical polarity) across plasma membranes of living cells.

Pedagogical Value
Encourages students to extrapolate the concept of membrane polarisation—which NCERT primarily discusses in the context of neurons—to general cell biology, reinforcing that resting membrane potential is a universal characteristic of living animal cells.

NCERT-Based Explanation
In neurophysiology, “resting” refers specifically to the state in which a neuron is not conducting an electrical impulse, not to metabolic dormancy. As a living cell, a resting neuron continuously performs metabolic processes—such as driving Na⁺/K⁺ pumps—to maintain cellular homeostasis and membrane potential.
Pedagogical Value
Tests reading precision and prevents students from confusing neurophysiological “rest” (absence of action potentials) with metabolic inactivity.

NCERT-Based Explanation
The Assertion is true. NCERT highlights the presence of Nissl granules in the cell body and dendrites of neurons, which function primarily in protein synthesis.
The Reason is true. Nissl granules are structural aggregations of Rough Endoplasmic Reticulum (RER) and free ribosomes.
Since ribosomes and RER are the cellular organelles responsible for protein synthesis, the Reason correctly explains the Assertion.
Pedagogical Value
This question bridges neuronal cellular anatomy (Nissl bodies) with fundamental cell biology concepts (RER and ribosome function in protein synthesis).

NCERT-Based Explanation
NCERT states that the gaps between two adjacent myelin sheaths are called nodes of Ranvier. The assertion is false because the gaps are not between two adjacent neuron’s myelin sheaths; they are between two adjacent myelin sheaths of the same myelinated nerve fibre (axon).
The reason is also false because the nodes of Ranvier, not the neurons, are named after the French anatomist Louis-Antoine Ranvier.

Pedagogical Value
This question contains two subtle wording traps. The first tests whether students recognise that nodes of Ranvier are gaps between adjacent myelin sheaths along a single myelinated axon, not between the myelin sheaths of adjacent neurons. The second checks whether students notice that the eponym Ranvier refers to the nodes, not the neurons. It rewards careful reading and precise interpretation of anatomical terminology.

NCERT-Based Explanation
The Assertion is false. NCERT states that Nissl’s granules are present in the cytoplasm of the cell body (cyton) and dendrites, not inside the nucleus.
The Reason is true. The cyton (cell body) contains cytoplasm along with typical cellular organelles and a well-defined nucleus.
Pedagogical Value
This question addresses a subcellular location misconception. It tests whether students distinguish between different regions of the cell body (cytoplasm versus nucleus), preventing them from incorrectly placing cytoplasmic granular bodies inside the nucleus.

NCERT-Based Explanation
According to NCERT, ionic gradients across the resting membrane are maintained by the active transport of ions by the sodium-potassium pump, which transports 3 Na⁺ outwards for 2 K⁺ into the cell. While both statements are scientifically true, generating the concentration gradient is the functional outcome of ion transport, not its causal explanation.
Pedagogical Value
Trains students to distinguish cause from effect in biological mechanisms, ensuring they recognise that ion pumping creates the concentration gradient rather than the gradient causing the pumping action.

NCERT-Based Explanation
NCERT states that Nissl’s granules are present in the cyton and dendrites but are absent from the axon. Within the cyton, the nucleus does not contain Nissl’s granules because protein synthesis (translation) occurs in the cytoplasm, not inside the nucleus. Therefore, Nissl’s granules are not present in all compartments of the cyton. Hence, both the assertion and the reason are true, and the reason correctly explains the assertion.

Pedagogical Value
NCERT mentions the presence of Nissl’s granules in the cyton but does not explicitly discuss their intracellular distribution. This question encourages students to connect the role of Nissl’s granules in protein synthesis with the fact that translation occurs only in the cytoplasm, enabling them to infer why Nissl’s granules are absent from the nucleus. It promotes conceptual reasoning beyond direct textbook statements while remaining consistent with NCERT principles.

NCERT-Based Explanation
The Assertion is true. A nerve plexus is a network of intersecting nerve fibres (axons) through which nerve impulses travel across different parts of the body.
The Reason is false. A plexus does not contain only neurons; it consists primarily of nerve fibres (axons) along with supporting connective tissue, blood vessels, and neuroglial cells.
Pedagogical Value
This question tests whether students distinguish between entire neurons and nerve plexuses, reinforcing that a plexus is a structural network of nerve fibres, blood vessels, and connective tissue rather than merely an isolated group of neuronal cell bodies.

NCERT-Based Explanation
According to NCERT, when a neuron is not conducting an impulse (resting), the axonal membrane is comparatively more permeable to potassium ions (K⁺) and nearly impermeable to sodium ions (Na⁺). It is not completely impermeable to all ions. Furthermore, maintaining the resting membrane potential requires continuous active transport via the Na⁺/K⁺ pump, consuming significant ATP.

Pedagogical Value
Exposes absolute wording (“impermeable to ions”) by testing precision regarding differential membrane permeability (K⁺ vs Na⁺) while dispelling the misconception that a resting neuron uses minimal energy.

NCERT-Based Explanation
The Assertion is true. Excitation requires a resting membrane potential (polarization) that can be altered in response to a stimulus.
The Reason is true. Direct NCERT statement: “Neurons are excitable cells because their membranes are in a polarised state.”
Since resting membrane polarization is the fundamental physiological prerequisite for generating an action potential (excitability), the Reason correctly explains the Assertion.
Pedagogical Value
Connects resting membrane potential (polarization) directly to the physiological concept of cellular excitability in neurons.

NCERT-Based Explanation
The Assertion is true. NCERT states that myelinated nerve fibres are enveloped with Schwann cells, and unmyelinated nerve fibres are also enclosed by a Schwann cell (without forming a myelin sheath).
The Reason is false. NCERT explicitly states that unmyelinated nerve fibres enclosed by Schwann cells are “commonly found in autonomous and the somatic neural systems.” Thus, these neurons do possess Schwann cells.
Pedagogical Value
Reinforces that autonomic and somatic unmyelinated neurons are supported by Schwann cells, dispelling the myth that Schwann cells are exclusive to myelinated axons.

NCERT-Based Explanation
The Assertion is false. Anatomically, “proximal” means closer to the point of origin. The proximal end of an axon is attached directly to the cell body (at the axon hillock), whereas the distal end extends far away from the cell body.
The Reason is false. The proximal end connects to the cyton; it is the distal end (axon terminals/knobs) that forms synapses with target cells or subsequent neurons.
Pedagogical Value
This question reinforces standard anatomical directional terms (“proximal” vs “distal”) in the context of neuronal morphology.

NCERT-Based Explanation
The Assertion is true. Direct NCERT statement: Dendrites transmit impulses towards the cell body (cyton).
The Reason is false. Nerve impulses propagate along the axonal membrane (axolemma), not “in” the myelin sheath. The myelin sheath serves as an insulating fatty layer around the axon that allows saltatory conduction across nodes of Ranvier, but it is not the conducting medium itself.
Pedagogical Value
This question tests whether students distinguish between conducting structures (dendrites/axons) and insulating protective structures (myelin sheath).

NCERT-Based Explanation
According to NCERT, the resting axonal membrane is impermeable to negatively charged proteins present in the axoplasm. However, large macromolecules such as proteins cannot freely diffuse across the lipid bilayer regardless of charge, making the Reason statement scientifically false.
Pedagogical Value
Traps students who assume logical symmetry (negatively charged vs positively charged) rather than evaluating actual membrane transport principles and exact NCERT details.

NCERT-Based Explanation
The Assertion is false. NCERT explicitly states that an unmyelinated nerve fibre is enclosed by a Schwann cell (which does not form a concentric myelin sheath around the axon).
The Reason is true. Schwann cells are neuroglial (glial) cells of the peripheral nervous system.
Pedagogical Value
Addresses the common misconception that unmyelinated neurons lack Schwann cells or glial support entirely. It reinforces that unmyelinated fibres are still enclosed by Schwann cells, but lack a wrapped myelin sheath.

NCERT-Based Explanation
The Assertion is true as a biological fact. The entire nervous system—including all central and peripheral neurons—is derived from embryonic ectoderm (neural tube and neural crest).
The Reason is false. “Neuro-endodermal cavity” is a non-existent biological term. Endoderm does not give rise to neural tissue.
Pedagogical Value
This question prevents students from being misled by fabricated technical terms (“neuro-endodermal cavity”) and reinforces embryological germ layer tissue origins.

NCERT-Based Explanation
The Assertion is false. NCERT states that the visceral nervous system transmits impulses both from the CNS to the viscera (efferent/motor) and from the viscera to the CNS (afferent/sensory), making transmission bidirectional overall.
The Reason is false. Transmission is not restricted to moving from viscera to CNS; efferent visceral fibers carry regulatory signals from the CNS to visceral organs and smooth muscles.
Pedagogical Value
This question tests whether students understand that autonomic/visceral regulation requires a two-way loop (sensory input to CNS and motor output from CNS) rather than unidirectional flow.

NCERT-Based Explanation
The Assertion is false. NCERT explicitly states that unmyelinated nerve fibres are enclosed by a Schwann cell.
The Reason is true. Direct NCERT statement: Unmyelinated nerve fibres are “commonly found in autonomous and the somatic neural systems.”
Pedagogical Value
Tests whether students confuse the absence of a myelin sheath with the absence of Schwann cells in autonomic and somatic unmyelinated neurons.

NCERT-Based Explanation
The Assertion is false. Neurotransmitters are released across the synaptic cleft and act locally on the postsynaptic membrane; they are not carried throughout the body by the circulatory system like classical hormones.
The Reason is true. Neuroendocrine (neurosecretory) cells are specialized neurons that synthesize and release chemical signals directly into the bloodstream.
Pedagogical Value
This question tests whether students can distinguish between local synaptic transmission and systemic endocrine signaling, preventing them from conflating the delivery mechanisms of neurotransmitters and hormones.

NCERT-Based Explanation
The Assertion is true. Direct NCERT statement: “The myelinated nerve fibres are enveloped with Schwann cells, which form a myelin sheath around the axon.”
The Reason is true. Myelin acts as an insulating layer that prevents ion leakage along the axon, facilitating saltatory conduction and thereby increasing impulse conduction speed and efficiency.
Because the lipid-rich insulating nature of myelin provides rapid conduction, the Reason correctly explains the functional significance of the myelin sheath formed around the axon.
Pedagogical Value
Connects the structural feature of Schwann cell-derived myelination with its physiological role in rapid electrical insulation and saltatory conduction.