Neural Control and Coordination (NCERT Practice Paper)

Q1. The neural system provides an organized network of ______ for quick coordination.

Correct Answer: (b)
The neural system uses specific nerve pathways that connect directly from one point to another, allowing rapid transmission of signals. This point-to-point arrangement ensures that impulses reach precise target cells quickly. Unlike hormonal signalling, neural communication is fast and localised. Such an organisation is crucial for immediate responses like reflex actions.

Q2. Assertion: Ions are transported across the axonal membrane against the concentration gradient. Reason: This is achieved by the active transport of the sodium-potassium pump.

Correct Answer: (a)
The sodium-potassium pump is an active transport mechanism that moves Na⁺ out and K⁺ in, both against their concentration gradients. This process requires ATP and is essential for maintaining the resting potential. The reason correctly identifies the pump as the means of this active transport, thus explaining the assertion.

Q3. Regarding neuron types based on axon count:
(i) Multipolar are found in cerebral cortex.
(ii) Bipolar are found in retina.
(iii) Unipolar are found in embryos.

Correct Answer: (a)
Multipolar neurons are abundant in the cerebral cortex (i). Bipolar neurons are typical of the retina and olfactory epithelium (ii). Unipolar neurons are predominantly seen during embryonic development (iii). All are correct.

Q4. Which are correct regarding synaptic transmission?
(i) Action potential triggers vesicle movement.
(ii) Neurotransmitters bind to specific receptors.
(iii) Potential developed can be excitatory or inhibitory.

Correct Answer: (a)
An arriving action potential causes synaptic vesicles to move and fuse with the presynaptic membrane (i). Released neurotransmitters bind to receptors on the postsynaptic membrane (ii). This binding can generate excitatory or inhibitory postsynaptic potentials (iii). All are correct.

Q5. Match the following for Brain stem:

A. Mid brain	Brain stem part
B. Pons	Brain stem part
C. Medulla	Brain stem part

Correct Answer: (a)
The brainstem consists of the midbrain, pons, and medulla oblongata. All three are integral parts of the brainstem, so the option 'All correct' is right.

Q6. Match the following:

Process	Description
A. Depolarisation	(II) Polarity reversal

Correct Answer: (a)
Depolarisation is the reversal of membrane polarity (inside becomes positive). The other options describe different phenomena, so the match to 'polarity reversal' is correct.

Q7. Which type of synapse is rare in the human system?

Correct Answer: (b)
Electrical synapses are uncommon in humans; they are more prevalent in invertebrates and some lower vertebrates. They allow direct ionic current flow through gap junctions, providing faster transmission but less flexibility. Chemical synapses are the predominant type in the human nervous system, offering modulatory control and signal amplification.

Q8. During resting potential, the axonal membrane is comparatively more permeable to:

Correct Answer: (b)
At rest, the axonal membrane is more permeable to potassium ions (K⁺) than to sodium ions (Na⁺). This selective permeability, along with the concentration gradient, causes K⁺ to leak out, making the inside negative relative to the outside. Sodium ions are largely blocked from entering, contributing to the resting membrane potential of about -70 mV.

Q9. Which are correct for 'Schwann cells'?
(i) Envelope myelinated fibres.
(ii) Form myelin sheath around axon.
(iii) Present in non-myelinated fibres but don't form sheath.

Correct Answer: (a)
Schwann cells envelop myelinated axons and form the myelin sheath (i and ii). In non-myelinated fibres, Schwann cells are still present but do not wrap tightly to form a sheath (iii). All statements are correct.

Q10. Which is true regarding nerve impulse conduction?
(i) Local current flows on the inner surface from site A to B.
(ii) Repolarisation restores the resting potential.
(iii) K+ diffuses outside the membrane to restore resting potential.

Correct Answer: (a)
During conduction, local currents flow along the inner membrane surface from the active region to the adjacent inactive region (i). Repolarisation involves K⁺ efflux, which restores the negative resting potential (ii and iii). All statements are accurate.

Q11. Match the neuron types in Column-I with their locations in Column-II:

Column-I (Neuron)	Column-II (Location)
A. Multipolar	(I) Embryonic stage
B. Bipolar	(II) Cerebral cortex
C. Unipolar	(III) Retina of eye

Correct Answer: (a)
Multipolar neurons are abundant in the cerebral cortex (A–II). Bipolar neurons are specialised sensory cells found in the retina (B–III). Unipolar neurons are primarily seen in the embryonic stage (C–I). This matching correctly aligns each neuron type with its typical location.

Q12. Assertion: Chemical synapses use neurotransmitters for impulse transmission. Reason: Synaptic vesicles in the axon terminal release these chemicals into the synaptic cleft.

Correct Answer: (a)
Chemical synapses rely on neurotransmitters to carry signals across the synaptic cleft. These neurotransmitters are stored in synaptic vesicles and are released by exocytosis when an action potential arrives. The reason describes this release mechanism, which is the core of chemical transmission, so it correctly explains the assertion.

Q13. Assertion: The cerebral cortex is referred to as the grey matter. Reason: It has a high concentration of neuron cell bodies which gives it a greyish appearance.

Correct Answer: (a)
The cerebral cortex indeed appears grey due to the densely packed neuronal cell bodies, dendrites, and unmyelinated fibres. This contrasts with the white matter underneath, which is rich in myelinated axons. The reason directly explains the greyish colour, making both statements true and causally linked.

Q14. Assertion: Resting axonal membrane is nearly impermeable to Na+. Reason: K+ diffuses outside the membrane during resting potential.

Correct Answer: (a)
Both statements are correct: the resting membrane has low Na⁺ permeability, and K⁺ does diffuse outward. However, the reason does not explain the low Na⁺ permeability; it describes a separate phenomenon (K⁺ efflux). The Na⁺ impermeability is due to the closure of voltage-gated Na⁺ channels, not because of K⁺ movement.

Q15. Regarding ion channels in neural membranes:
(i) They are selectively permeable.
(ii) They allow movement of different ions.
(iii) They are present on the axonal membrane.

Correct Answer: (a)
Ion channels are selectively permeable to specific ions (i). They allow the movement of Na⁺, K⁺, Cl⁻, etc., across the membrane (ii). They are embedded in the axonal membrane (iii). All are correct.

Q16. Assertion: Impulse transmission across an electrical synapse is always faster than across a chemical synapse. Reason: Electrical synapses are very common in the human body.

Correct Answer: (c)
Assertion is correct because electrical synapses allow direct ionic current flow and are faster than chemical synapses. However, the reason is incorrect because electrical synapses are rare in the human nervous system; chemical synapses are the predominant type. Therefore, while the assertion holds, the stated reason is false.

Q17. Correct statements for the cerebral cortex:
(i) Thrown into prominent folds.
(ii) Outer layer of cerebral hemispheres.
(iii) Contains motor and sensory areas.

Correct Answer: (a)
The cerebral cortex is the outer layer of the cerebral hemispheres and is highly folded (gyri and sulci) to increase surface area (i and ii). It contains distinct motor, sensory, and association areas (iii). All statements are correct.

Q18. The nerve fibres that transmit impulses from tissues/organs to the CNS are called:

Correct Answer: (b)
Afferent fibres carry sensory information from the periphery (skin, muscles, organs) towards the central nervous system. They are also known as sensory fibres. Efferent fibres, in contrast, carry motor commands away from the CNS to effectors. This directional flow is fundamental to the reflex arc and conscious sensation.

Q19. Assertion: Neurons are called excitable cells. Reason: Their membranes are in a polarised state.

Correct Answer: (a)
Neurons are excitable because they can generate and transmit electrical impulses, which is made possible by the polarised membrane (resting potential). The polarised state (inside negative relative to outside) creates a potential difference that can be disrupted by stimuli. Thus the reason accurately describes the basis of excitability.

Q20. Match the axonal transport pump:

Pump Name	Action
A. Sodium-potassium pump	(I) 3 Na+ out, 2 K+ in

Correct Answer: (a)
The sodium-potassium pump transports 3 Na⁺ out and 2 K⁺ in per ATP hydrolyzed. This is the correct stoichiometry, so the match is correct.

Q21. Which are true for midbrain and hindbrain?
(i) Cerebral aqueduct passes through midbrain.
(ii) Pons consists of fibre tracts.
(iii) Brain stem connects brain to spinal cord.

Correct Answer: (a)
The cerebral aqueduct runs through the midbrain (i). The pons contains transverse fibre tracts that connect different brain regions (ii). The brainstem (midbrain + pons + medulla) connects the brain to the spinal cord (iii). All statements are correct.

Q22. Assertion: Midbrain is characteristically small. Reason: It is located between the thalamus and pons.

Correct Answer: (a)
The midbrain is relatively small and is indeed situated between the thalamus (above) and pons (below). However, its location does not explain why it is small; size is a morphological feature, not determined by position. Both statements are true, but the reason does not account for the assertion.

Q23. Assertion: The PNS is divided into somatic and autonomic neural systems. Reason: Somatic neural system relays impulses to involuntary organs.

Correct Answer: (c)
The PNS indeed has a somatic division and an autonomic division. However, the somatic neural system controls voluntary skeletal muscles, not involuntary organs. Involuntary organs are under the autonomic system. Thus the assertion is correct, but the reason is false because it misattributes the function of the somatic system.

Q24. At a chemical synapse, the gap between the pre- and post-synaptic neurons is called:

Correct Answer: (c)
The synaptic cleft is the narrow fluid-filled space that separates the presynaptic membrane from the postsynaptic membrane. It is about 20-30 nm wide and allows neurotransmitters to diffuse across. This gap ensures that signals are transmitted chemically rather than electrically, enabling fine regulation of synaptic strength.

Q25. Assertion: Dendrites transmit impulses away from the cell body. Reason: Axons possess synaptic knobs.

Correct Answer: (a)
The assertion is incorrect because dendrites conduct impulses towards the cell body, not away. The reason is true: axons do have synaptic knobs (terminal boutons) for neurotransmitter release. Therefore, the assertion is false while the reason is true, making this the correct pairing.

Q26. Assertion: The inner surface of the resting axonal membrane is negatively charged. Reason: The membrane is impermeable to negatively charged proteins in the axoplasm.

Correct Answer: (a)
During resting potential, the inside of the axon is negative relative to the outside. This is largely due to the presence of large, negatively charged proteins that cannot cross the membrane. These impermeable anions contribute significantly to the negative intracellular charge, making the reason a correct explanation.

Q27. The process through which two or more organs interact and complement the functions of one another is called:

Correct Answer: (b)
Coordination is the harmonised working of different organs to achieve a common goal. It ensures that various tissues and systems function together efficiently. This interaction is essential for maintaining a stable internal environment and responding to external changes. Without coordination, the body would not be able to carry out complex activities smoothly.

Q28. The 'brain stem' forms the connections between the brain and the:

Correct Answer: (b)
The brainstem (comprising midbrain, pons, and medulla) connects the cerebrum and cerebellum to the spinal cord. It serves as a conduit for ascending and descending fibre tracts, as well as the origin of most cranial nerves. It also houses nuclei that control basic life-sustaining functions.

Q29. Identify the correct statements for synapses:
(i) Electrical synapses allow direct current flow.
(ii) Chemical synapses use neurotransmitters.
(iii) Impulse transmission across chemical synapse is faster.

Correct Answer: (a)
Electrical synapses allow direct ionic current flow via gap junctions (i). Chemical synapses transmit signals using neurotransmitters (ii). However, chemical synapses are slower than electrical synapses, so (iii) is false. Thus only (i) and (ii) are correct.

Q30. Regarding the generation of nerve impulse, which is correct?
(i) Na+ moves inside upon stimulus.
(ii) Polarity is reversed at the site of stimulus.
(iii) Rise in Na+ permeability is extremely short-lived.

Correct Answer: (a)
Stimulation opens Na⁺ channels, causing influx (i). This influx reverses the membrane polarity (depolarisation) at the active site (ii). The increase in Na⁺ permeability is brief because the channels quickly inactivate (iii). All statements are correct.

Q31. Assertion: Coordination is essential to maintain homeostasis. Reason: It is the process through which organs interact and complement each other.

Correct Answer: (a)
Coordination ensures that different organs work together harmoniously, which is exactly what maintains a stable internal environment (homeostasis). The reason correctly explains how coordination achieves this by integrating organ functions. Without such interaction, physiological parameters would fluctuate and disrupt homeostasis.

Q32. The junction between two neurons is called a:

Correct Answer: (a)
A synapse is the specialised junction where a neuron communicates with another neuron or an effector cell. It allows the transfer of information via electrical or chemical signals. The synaptic cleft separates the pre- and postsynaptic membranes. Neurotransmitters are released at chemical synapses to bridge this gap and continue the signal.

Q33. Match the limb components of the brain:

Term	Component
A. Limbic system	(I) Amygdala
B. Limbic system	(II) Hippocampus

Correct Answer: (a)
The limbic system includes both the amygdala and hippocampus, along with other structures like the hypothalamus. Both components are correct parts of the limbic system, so the answer 'Both are correct' is accurate.

Q34. Identify the correct statements about the hypothalamus:
(i) It lies at the base of the thalamus.
(ii) It contains centres for thermoregulation.
(iii) It secretes hypothalamic hormones.

Correct Answer: (a)
The hypothalamus is situated below the thalamus (i). It has centres that regulate body temperature, hunger, thirst, and other homeostatic functions (ii). It also produces releasing and inhibiting hormones that control the pituitary gland (iii). All statements are true.

Q35. Match the neurotransmitter storage and release:

Term	Fact
A. Synaptic vesicles	(I) Contain neurotransmitters
B. Synaptic knob	(II) Bulb-like structure at axon end
C. Receptors	(III) Binding sites on post-synaptic membrane

Correct Answer: (a)
Synaptic vesicles store neurotransmitters (I). Synaptic knob is the swollen axon terminal (II). Receptors are proteins on the postsynaptic membrane that bind neurotransmitters (III). These are correctly matched.

Q36. Match the cranial meninges from outermost to innermost:

Layer Name	Position
A. Dura mater	(I) Middle
B. Arachnoid	(II) Innermost
C. Pia mater	(III) Outermost

Correct Answer: (a)
The cranial meninges are arranged from outermost to innermost as: dura mater (III), arachnoid (I), and pia mater (II). The dura is tough and fibrous, the arachnoid is delicate and web-like, and the pia is thin and adheres to the brain surface. This sequence is correctly matched in option A.

Q37. The 'corpora quadrigemina' are four round swellings located in the:

Correct Answer: (b)
The corpora quadrigemina are four rounded elevations on the dorsal aspect of the midbrain. They consist of two superior colliculi (involved in visual reflexes) and two inferior colliculi (involved in auditory reflexes). These structures are important for orienting movements in response to visual and auditory stimuli.

Q38. The sodium-potassium pump transports ______ Na+ outwards for ______ K+ into the cell.

Correct Answer: (b)
The sodium-potassium pump actively moves 3 sodium ions out of the cell and 2 potassium ions into the cell, against their concentration gradients. This process consumes ATP and is crucial for maintaining the resting potential. It helps keep the intracellular environment high in K⁺ and low in Na⁺, which is essential for generating action potentials.

Q39. Match the following:

Part	Nature
A. Synaptic cleft	(I) Fluid-filled space

Correct Answer: (a)
The synaptic cleft is a fluid-filled gap between neurons at a chemical synapse. It is not bony or air-filled, so the match is correct.

Q40. The autonomic neural system is further classified into:

Correct Answer: (c)
The autonomic nervous system (ANS) regulates involuntary functions and is divided into sympathetic and parasympathetic divisions. The sympathetic system prepares the body for fight-or-flight responses, while the parasympathetic system promotes rest-and-digest activities. Both divisions work antagonistically to maintain homeostasis. The somatic system, in contrast, controls voluntary muscles.

Q41. Nissl’s granules are found in which part of the neuron?

Correct Answer: (c)
Nissl's granules are rough endoplasmic reticulum aggregates present in the cell body (soma) and dendrites, but absent in the axon and synaptic knob. They are involved in protein synthesis, which is essential for neuronal function and maintenance. Their presence is a characteristic feature of neurons and helps distinguish them from other cells.

Q42. Assertion: Limbic system is called the 'emotional brain'. Reason: It is involved in motivation and expression of emotional reactions.

Correct Answer: (a)
The limbic system is widely known as the emotional brain because it plays a key role in processing emotions, motivation, and memory. The reason accurately states its involvement in motivation and emotional expression, which directly supports why it earns that nickname.

Q43. Match the nerve pairs:

Type	Pairs
A. Cranial nerves	(I) 10 pairs

Correct Answer: (b)
In humans, there are 12 pairs of cranial nerves. The option 'A–12 pairs' is correct because the 10 pairs mentioned is not accurate for humans. Cranial nerves are numbered I to XII and emerge directly from the brain.

Q44. Identify correct statements for the brain protection:
(i) Skull protects the brain.
(ii) Dura mater is the outermost layer.
(iii) Pia mater is in contact with brain tissue.

Correct Answer: (a)
The brain is protected by the skull (cranium) (i). The meninges consist of dura mater (outer), arachnoid (middle), and pia mater (inner) that directly contacts the brain (ii and iii). All are correct.

Q45. Match the Following:

A. Cerebrum	Forebrain
B. Thalamus	Forebrain
C. Hypothalamus	Forebrain

Correct Answer: (a)
The cerebrum, thalamus, and hypothalamus are all parts of the forebrain. This classification is correct for all three structures, so 'All correct' is the appropriate choice.

Q46. The electrical potential difference across the plasma membrane at the site of excitation is called:

Correct Answer: (b)
An action potential is the rapid, transient change in membrane potential that occurs when a neuron is excited. It involves depolarisation followed by repolarisation. This electrical signal travels along the axon and is the basis of nerve impulse transmission. The resting potential is the baseline voltage, while depolarisation and repolarisation are phases of the action potential.

Q47. Match the stimulus response speed:

Synapse Type	Speed
A. Electrical	(I) Faster
B. Chemical	(II) Slower

Correct Answer: (a)
Electrical synapses allow direct ionic current flow and are faster (I). Chemical synapses require neurotransmitter release and diffusion, making them slower (II). This speed difference is correctly matched.

Q48. Match electrical potential terms:

State	Term
A. Potential across resting membrane	(I) Resting potential
B. Potential across excited membrane	(II) Action potential

Correct Answer: (a)
Resting membrane potential is the steady voltage across an unstimulated neuron (I). The potential during excitation is the action potential (II). This matching correctly distinguishes the two states.

Q49. Assertion: Myelinated nerve fibres are found in spinal and cranial nerves. Reason: These fibres are enveloped with Schwann cells which form a myelin sheath.

Correct Answer: (a)
Many spinal and cranial nerves are myelinated, and this myelin is produced by Schwann cells in the PNS. The myelin sheath insulates the axon and speeds up impulse conduction. The reason correctly describes the cellular mechanism, thus explaining the assertion.

Q50. Which of the following is correct?
(i) Alfonso Corti was an Italian anatomist.
(ii) Organ of Corti is in the cochlea.
(iii) Hair cells convert sound to nerve impulses.

Correct Answer: (a)
Alfonso Corti was indeed an Italian anatomist who described the organ of Corti (i). The organ of Corti is located in the cochlea of the inner ear (ii). Its hair cells transduce mechanical sound vibrations into nerve impulses (iii). All statements are correct.

Q51. Which part of the brain is the major coordinating centre for sensory and motor signaling?

Correct Answer: (b)
The thalamus is a large relay station located in the diencephalon. It processes and relays sensory information (except smell) to the appropriate cortical areas and also plays a role in motor control. It acts as a gateway, filtering and modulating signals before they reach the cerebral cortex.

Q52. The gaps between two adjacent myelin sheaths are called:

Correct Answer: (b)
Nodes of Ranvier are regular gaps in the myelin sheath along a myelinated axon. They expose the axonal membrane to the extracellular fluid, enabling saltatory conduction. This arrangement speeds up impulse transmission by allowing the signal to 'jump' from node to node. The myelin sheath itself is formed by Schwann cells in the PNS.

Q53. Assertion: Action potential is also termed as a nerve impulse. Reason: It is the electrical potential difference across the plasma membrane at a site of stimulus.

Correct Answer: (a)
An action potential is indeed the nerve impulse; it is a brief reversal of membrane potential that propagates along the axon. The reason correctly defines it as the potential difference at the stimulated site. Therefore, the reason provides a valid definition of the action potential, thereby supporting the assertion.

Q54. The hemispheres of the cerebrum are connected by a tract of nerve fibres called:

Correct Answer: (c)
The corpus callosum is a broad band of myelinated nerve fibres that connects the left and right cerebral hemispheres. It allows interhemispheric communication, enabling integration of sensory, motor, and cognitive functions. Without it, the two halves of the brain would operate independently.

Q55. Assertion: Visceral nervous system is a part of PNS. Reason: It carries impulses to and from the viscera.

Correct Answer: (a)
The visceral nervous system, often synonymous with the autonomic nervous system, is indeed a component of the peripheral nervous system. Its function is to innervate internal organs (viscera). The reason describes this function, thereby supporting its classification as part of the PNS.

Q56. Match the structure in Column-I with its description in Column-II:

Column-I	Column-II
A. Axoneme	(I) Infoldings of cell membrane
B. Mesosome	(II) Core of cilia/flagella
C. Synapse	(III) Junction between neurons

Correct Answer: (a)
Axoneme is the microtubular core of cilia and flagella (II). Mesosomes are infoldings of the plasma membrane in bacteria (I). Synapse is the junction between two neurons (III). These definitions are correctly paired.

Q57. Match the ionic events with the membrane state:

Column-I	Column-II
A. Na+ influx	(I) Polarisation
B. Na+/K+ pump	(II) Repolarisation
C. K+ efflux	(III) Depolarisation

Correct Answer: (a)
Na⁺ influx causes depolarisation (III). The Na⁺/K⁺ pump maintains polarisation (I) by restoring ion gradients. K⁺ efflux leads to repolarisation (II). This matching correctly links each ion movement to its effect on membrane potential.

Q58. Assertion: Neurotransmitters are released upon the arrival of action potential at the axon terminal. Reason: They are stored in synaptic vesicles.

Correct Answer: (a)
When an action potential reaches the presynaptic terminal, it triggers the fusion of synaptic vesicles with the membrane, releasing neurotransmitters. The vesicles are the storage sites for these chemicals, so the reason explains how they become available for release. Thus, the reason correctly explains the assertion.

Q59. Assertion: Corpus callosum is a tract of nerve fibres. Reason: It connects the left and right cerebral hemispheres.

Correct Answer: (a)
The corpus callosum is indeed a large bundle of myelinated fibres that connects the two hemispheres. The reason correctly identifies its function, which is precisely what makes it a 'tract'—a collection of fibres linking brain regions. Therefore, the reason explains the assertion.

Q60. Match the meninges depth:

A. Dura mater	Outer
B. Arachnoid	Middle
C. Pia mater	Inner

Correct Answer: (a)
The dura mater is the outermost, arachnoid is the middle, and pia mater is the innermost layer of the meninges. All three statements are correct.

Q61. Match the scientist with his discovery:

Scientist	Discovery
A. Robert Brown	(I) Nucleus
B. Alfonso Corti	(II) Organ of Corti

Correct Answer: (a)
Robert Brown discovered the nucleus (I). Alfonso Corti described the organ of Corti in the inner ear (II). These historical contributions are accurately matched.

Q62. Neurons with one axon and two or more dendrites are called:

Correct Answer: (c)
Multipolar neurons have a single axon and multiple dendrites, allowing them to receive inputs from many sources. They are the most common type in the human nervous system, especially in the cerebral cortex and spinal cord. Unipolar neurons have only one process, while bipolar have one axon and one dendrite. This structural diversity supports different functional roles in neural circuits.

Q63. Match the following divisions of PNS:

Column-I	Column-II
A. Somatic neural system	(I) Involuntary organs / smooth muscles
B. Autonomic neural system	(II) Skeletal muscles
C. Visceral neural system	(III) Travel to/from viscera

Correct Answer: (a)
Somatic system controls skeletal muscles (II). Autonomic system regulates involuntary organs and smooth muscles (I). Visceral system carries impulses to/from viscera (III). This matches the functional divisions of the peripheral nervous system.

Q64. Which division of the human neural system includes the brain and the spinal cord?

Correct Answer: (d)
The central nervous system (CNS) is the main processing centre and consists of the brain and spinal cord. It integrates incoming information and generates outgoing commands. The PNS (peripheral nervous system) lies outside the CNS. The CNS is protected by bony structures and meninges, and it is the site of higher functions like thinking and memory.

Q65. Identify the correct phylum/group being described?
(i) They detect, receive and transmit stimuli.
(ii) They are highly specialized cells.
(iii) They make up the neural system.

Correct Answer: (a)
Neurons are specialised cells that detect, receive, and transmit stimuli. They form the structural and functional units of the nervous system. The description matches neurons perfectly.

Q66. Assertion: Brain acts as the 'command and control system'. Reason: It controls voluntary movements and the functioning of vital involuntary organs.

Correct Answer: (a)
The brain integrates and coordinates all body activities, both voluntary (e.g., skeletal muscle movements) and involuntary (e.g., heartbeat, breathing). This dual role makes it the central command centre. The reason highlights these two aspects, providing a comprehensive justification for the assertion.

Q67. Select correct statements about the autonomic neural system:
(i) Transmits impulses to involuntary organs.
(ii) Classified into sympathetic and parasympathetic systems.
(iii) Regulates skeletal muscles.

Correct Answer: (a)
The autonomic system innervates involuntary organs (i) and is divided into sympathetic and parasympathetic (ii). It does not control skeletal muscles; that is the role of the somatic system, so (iii) is false. Therefore (i) and (ii) are correct.

Q68. The part of the brain that controls body temperature and the urge for eating is:

Correct Answer: (c)
The hypothalamus is a small but critical region below the thalamus. It contains homeostatic centres that regulate body temperature, hunger, thirst, sleep, and endocrine functions. It also influences emotional behaviour and connects the nervous system to the endocrine system via the pituitary gland.

Q69. Identify correct features of 'Resting Potential':
(i) Inner surface is negatively charged.
(ii) Axoplasm has high K+.
(iii) Outer surface is positively charged.

Correct Answer: (a)
At resting potential, the inside of the membrane is negative relative to the outside (i). The axoplasm contains a high concentration of K⁺ (ii), while the extracellular fluid has more Na⁺. The outside is positively charged (iii). All features are correct.

Q70. Match the nerve fibre with its feature:

Column-I	Column-II
A. Myelinated	(I) Schwann cells present, no sheath
B. Non-myelinated	(II) Schwann cells present, with sheath

Correct Answer: (a)
Myelinated fibres have Schwann cells that wrap around the axon to form a myelin sheath (II). Non-myelinated fibres have Schwann cells but no myelin sheath (I). This distinction is correctly paired.

Q71. Which region of the brain controls respiration and cardiovascular reflexes?

Correct Answer: (c)
The medulla oblongata is the lowest part of the brainstem and contains vital autonomic centres. It regulates respiratory rate, heart rate, blood pressure, and other involuntary functions such as swallowing and vomiting. Damage to the medulla can be life-threatening due to loss of these essential reflexes.

Q72. Assertion: Dura mater is the innermost layer of the cranial meninges. Reason: It is in contact with the brain tissue.

Correct Answer: (a)
The assertion is false because the dura mater is the outermost meningeal layer, not the innermost. The reason is also false because the pia mater is the layer that directly contacts the brain tissue. Therefore, both statements are incorrect.

Q73. Select correct statements for 'white matter':
(i) Constitutes the inner part of cerebral hemisphere.
(ii) Contains myelinated nerve fibres.
(iii) Has an opaque white appearance.

Correct Answer: (a)
White matter lies deep to the cortex and is composed of myelinated axons (i and ii). Its white colour is due to the myelin sheath (iii). All statements are correct.

Q74. Assertion: Unipolar neurons are usually found in the embryonic stage. Reason: They consist of a cell body with one axon and one dendrite.

Correct Answer: (c)
The assertion is true: unipolar neurons are predominantly seen during embryonic development. However, the reason is false because unipolar neurons have a single process that branches into an axon and a dendrite, but they do not have separate axon and dendrite like bipolar cells. The description given fits bipolar neurons, not unipolar. Hence the reason does not correctly characterise unipolar neurons.

Q75. Regarding the cerebellum:
(i) Part of hindbrain.
(ii) Convoluted surface.
(iii) Located in the forebrain.

Correct Answer: (a)
The cerebellum is a hindbrain structure (i) and has a highly folded cortex (ii). It is not part of the forebrain, so (iii) is false. Thus only (i) and (ii) are correct.

Q76. Which part of the brain has a very convoluted surface to provide space for more neurons?

Correct Answer: (c)
The cerebellum has a highly folded cortex with numerous gyri and sulci, increasing its surface area to accommodate a large number of neurons. This extensive folding is essential for its role in coordinating fine motor movements, balance, and posture. The convolutions allow a large number of Purkinje cells to be packed into a relatively small volume.

Q77. Which of the following is correct regarding 'Association areas'?
(i) They are in the cerebral cortex.
(ii) They are neither clearly sensory nor motor.
(iii) They handle memory and communication.

Correct Answer: (a)
Association areas are regions of the cerebral cortex that are not strictly sensory or motor (i and ii). They integrate information from multiple modalities and are involved in memory, language, and communication (iii). All statements are true.

Q78. Match the Following:

Column-I	Column-II
A. Grey matter	(I) Greyish appearance due to cell bodies
B. White matter	(II) White appearance due to myelin
C. Association areas	(III) Intersensory associations/memory

Correct Answer: (a)
Grey matter contains neuronal cell bodies giving a greyish tint (I). White matter is myelinated, hence white (II). Association areas are involved in higher functions like memory and intersensory integration (III). The matching is correct.

Q79. Match the cell body components:

Neuron part	Contains
A. Cell body	Organelles and Nissl's granules

Correct Answer: (a)
The neuronal cell body (soma) contains the nucleus, organelles, and Nissl's granules (rough ER). Therefore, the statement 'A is correct' accurately describes its contents.

Q80. Assertion: The cerebellum provides additional space for many more neurons. Reason: It has a very convoluted surface.

Correct Answer: (a)
The cerebellar cortex is highly folded, increasing its surface area significantly. This folding allows a greater number of neurons (especially Purkinje cells) to be packed into the available volume, enhancing its computational capacity. The reason directly explains the structural basis for the assertion.

Q81. Regarding the resting state of a neuron, which statements are correct?
(i) The membrane is nearly impermeable to Na+.
(ii) The membrane is comparatively more permeable to K+.
(iii) The axoplasm contains high concentration of K+.

Correct Answer: (a)
At rest, the axonal membrane is much less permeable to Na⁺ than to K⁺. The permeability to K⁺ is higher, and the intracellular fluid (axoplasm) has a high K⁺ concentration. All three statements are accurate descriptions of the resting neuron.

Q82. Which of the following describes the grey matter correctly?
(i) It is found in the cerebral cortex.
(ii) It appears grey due to neuron cell bodies.
(iii) It contains association areas.

Correct Answer: (a)
Grey matter is present in the cerebral cortex (i) and its colour comes from densely packed neuronal cell bodies (ii). The association areas, which integrate information, are also part of the cortex (iii). All statements are true.

Q83. The very thin middle layer of the cranial meninges is:

Correct Answer: (c)
The arachnoid mater is the delicate, web-like middle layer of the meninges. It lies between the tough dura mater (outer) and the pia mater (inner). The subarachnoid space beneath it contains cerebrospinal fluid, which cushions the brain. The arachnoid is avascular and does not directly contact the brain tissue.

Q84. Match the Following:

Component	Description
A. Cerebral aqueduct	(I) Canal passing through midbrain
B. Diencephalon	(II) Unpaired part of forebrain
C. Brain box	(III) Cranium

Correct Answer: (a)
Cerebral aqueduct is a canal in the midbrain (I). Diencephalon is the unpaired part of forebrain (II). Brain box is the cranium (III). These definitions are correctly matched.

Q85. Assertion: White matter appears white due to myelin sheath. Reason: The inner part of the cerebral hemisphere contains myelinated nerve fibres.

Correct Answer: (a)
The white colour of white matter comes from the lipid-rich myelin sheaths surrounding axons. The inner region of the cerebral hemispheres is indeed composed of myelinated fibre tracts. Thus, the reason correctly explains why that area appears white, linking structure and appearance.

Q86. Assertion: Hypothalamus is involved in the regulation of sexual behaviour. Reason: It forms a part of the limbic system along with the amygdala and hippocampus.

Correct Answer: (a)
The hypothalamus is indeed part of the limbic system, which is responsible for emotions, motivation, and sexual behaviour. The reason correctly states its anatomical association with other limbic structures, which together coordinate these functions. Thus the reason explains how the hypothalamus influences sexual behaviour.

Q87. Regarding the CNS and PNS:
(i) CNS is the site of information processing.
(ii) PNS consists of all nerves associated with CNS.
(iii) PNS includes cranial and spinal nerves.

Correct Answer: (a)
The CNS (brain and spinal cord) processes and integrates information (i). The PNS includes all nerves that connect the CNS to the rest of the body (ii), and these include cranial and spinal nerves (iii). All statements are correct.

Q88. Which statements about the limbic system are true?
(i) It includes the amygdala and hippocampus.
(ii) It interacts with the hypothalamus.
(iii) It is involved in the expression of fear and motivation.

Correct Answer: (a)
The limbic system comprises the amygdala, hippocampus, and other structures (i). It has strong connections with the hypothalamus (ii). It plays a key role in emotional responses such as fear and motivation (iii). All are correct.

Q89. In Hydra, the neural organization is composed of:

Correct Answer: (b)
Hydra has a diffuse nerve net rather than a centralised brain or ganglia. This network of interconnected neurons spreads throughout the body and enables simple responses to stimuli. It lacks specialised nerve cords or a true CNS. This primitive organisation is sufficient for its basic movements and feeding behaviour.

Q90. Identify correct statements for a neuron structure:
(i) Dendrites transmit impulses towards the cell body.
(ii) Axon terminates in a synaptic knob.
(iii) Dendrites contain Nissl's granules.

Correct Answer: (a)
Dendrites carry signals toward the soma (i). The axon ends in synaptic knobs (boutons) that release neurotransmitters (ii). Nissl's granules are present in the cell body and dendrites, but not in the axon (iii). Thus all three statements are correct.

Q91. Which of the following is/are true for the medulla oblongata?
(i) It is connected to the spinal cord.
(ii) It controls respiration.
(iii) it controls cardiovascular reflexes.

Correct Answer: (a)
The medulla oblongata is continuous with the spinal cord (i). It houses the respiratory centre (ii) and cardiovascular centres that regulate heart rate and blood pressure (iii). Thus, all three statements are correct.

Q92. Regarding 'Action Potential':
(i) Membrane becomes permeable to Na+.
(ii) Polarity is reversed at the site.
(iii) Impulse is generated.

Correct Answer: (a)
During action potential, Na⁺ permeability increases dramatically (i), causing depolarisation and polarity reversal (ii). This transient change constitutes the nerve impulse (iii). All statements are correct.

Q93. Assertion: The medulla oblongata is an essential part of the brain stem. Reason: It contains centres for vital functions like respiration and gastric secretions.

Correct Answer: (a)
The medulla is indeed a critical component of the brainstem. Its role in regulating respiration, cardiovascular activity, and gastric reflexes makes it indispensable for survival. The reason provides a valid justification for why the medulla is essential, as these functions are vital.

Q94. Match the following brain parts with their functions:

Column-I	Column-II
A. Hypothalamus	(I) Respiration, gastric secretions
B. Cerebellum	(II) Precision and convoluted surface
C. Medulla	(III) Body temperature, hunger
D. Thalamus	(IV) Sensory and motor signaling

Correct Answer: (a)
Hypothalamus regulates body temperature and hunger (III). Cerebellum is associated with precision and has a convoluted surface (II). Medulla controls respiration and gastric reflexes (I). Thalamus relays sensory and motor signals (IV). This functional mapping is accurate.

Q95. Match sensory organs:

Sense	Organ
A. Vision	Eyes
B. Hearing	Ear (Tympanum)

Correct Answer: (a)
Vision is mediated by the eyes, and hearing is mediated by the ears (with the tympanum being part of the middle ear). Both sensory organ associations are correct.

Q96. Match the brain region with its constituents:

Column-I	Column-II
A. Forebrain	(I) Corpora quadrigemina
B. Midbrain	(II) Cerebrum, Thalamus
C. Hindbrain	(III) Pons, Cerebellum, Medulla

Correct Answer: (a)
Forebrain consists of cerebrum and thalamus (II). Midbrain contains corpora quadrigemina (I). Hindbrain includes pons, cerebellum, and medulla (III). This correctly classifies the major brain regions.

Q97. Match the Following:

Column-I	Column-II
A. K+ permeability	(I) Resting potential
B. Na+ permeability	(II) Action potential

Correct Answer: (a)
During resting potential, K⁺ permeability is high (I). During action potential, Na⁺ permeability increases dramatically (II). This functional relationship is correctly paired.

Q98. Assertion: The medulla oblongata is connected to the spinal cord. Reason: It contains centres for cardiovascular reflexes.

Correct Answer: (a)
Both the assertion and the reason are true: the medulla is continuous with the spinal cord, and it does contain cardiovascular centres. However, the reason does not explain the connection; it describes a separate function. The anatomical connection is due to its position in the brainstem, not because of its reflex centres.

Q99. Bipolar neurons are commonly found in the:

Correct Answer: (c)
Bipolar neurons have one axon and one dendrite and are specialised for sensory functions. They are typically found in the retina of the eye, where they transmit visual signals from photoreceptors to ganglion cells. They also occur in the olfactory epithelium and inner ear. Their bipolar shape allows direct relay of sensory information.

Q100. A stimulus causes a rapid influx of which ion into the cell, leading to depolarization?

Correct Answer: (c)
When a neuron is stimulated, voltage-gated sodium channels open, allowing a rapid influx of Na⁺ ions. This sudden positive charge entry reduces the membrane potential, causing depolarisation. If the threshold is reached, an action potential is initiated. The inward Na⁺ current is the primary event that triggers the rising phase of the action potential.