10. How many pairs of spinal nerves normally arise from the human spinal cord?
[WBCS Preliminary (2019)]
- (A) 12 pairs
- (B) 31 pairs
- (C) 31 single nerves
- (D) 12 single nerves
Answer: (B) 31 pairs
Explanation: The 31 pairs comprise eight cervical, twelve thoracic, five lumbar, five sacral and one coccygeal pair. Spinal nerves are mixed nerves after their dorsal sensory and ventral motor roots join. They link the spinal cord with muscles, skin and viscera.
9. How many pairs of cranial nerves are present in a typical human?
[RPSC Senior Teacher Grade II, Science (18 Feb 2019)]
- (A) 6 pairs
- (B) 12 pairs
- (C) 24 pairs
- (D) 20 pairs
Answer: (B) 12 pairs
Explanation: There are twelve pairs of cranial nerves. Some are predominantly sensory, such as the optic nerve; others are motor or mixed. The vagus nerve is especially important for parasympathetic functions in the thoracic and abdominal organs.
8. The nicotinic acetylcholine receptor at a chemical synapse belongs to which class?
[CSIR-UGC NET Life Sciences (15 Dec 2019)]
- (A) Ligand-gated cation channel
- (B) Ligand-gated anion channel
- (C) Voltage-gated cation channel
- (D) Voltage-gated anion channel
Answer: (A) Ligand-gated cation channel
Explanation: The nicotinic acetylcholine receptor opens when acetylcholine binds, allowing mainly positive ions to cross its membrane pore. It is therefore a ligand-gated cation channel. At skeletal neuromuscular junctions, its activation produces end-plate depolarisation leading toward muscle excitation.
7. Which sets contain correctly identified neurotransmitters:
(a) acetylcholine and GABA,
(b) dopamine and noradrenaline,
(c) lysine and histamine,
(d) pyruvate and acetyl-CoA?
[MPSC Subordinate Services Preliminary (2019)]
- (A) (a) only
- (B) (c) only
- (C) (a) and (b)
- (D) (c) and (d)
Answer: (C) (a) and (b)
Explanation: Acetylcholine, GABA, dopamine and noradrenaline are established neurotransmitters. Lysine is chiefly an amino acid rather than a classical transmitter, so its pairing with histamine is unsuitable here. Pyruvate and acetyl-CoA are metabolic intermediates, not standard synaptic neurotransmitter pairs.
6. Which of the following represents the correct simplified circuit of a reflex arc?
[UPSC NDA, General Ability Test (9 Sep 2018)]
- (A) Effector → sensory neuron → spinal cord → motor neuron → receptor
- (B) Receptor → sensory neuron → spinal cord → motor neuron → effector
- (C) Receptor → sensory neuron → brain → motor neuron → effector
- (D) Sensory neuron → receptor → brain → effector → motor neuron
Answer: (B) Receptor → sensory neuron → spinal cord → motor neuron → effector
Explanation: The receptor detects a stimulus, the sensory neuron conveys it to spinal circuitry, and a motor neuron activates an effector. Although additional interneurons are frequent, this simplified order is correct. Such circuits permit a rapid involuntary response before conscious evaluation.
5. Which organ’s functional tissue lacks pain receptors and would not itself feel a needle prick?
[UPPSC Civil Services Preliminary (2017)]
- (A) Skin
- (B) Brain
- (C) Heart
- (D) Eye
Answer: (B) Brain
Explanation: Brain parenchyma itself lacks pain-sensitive nociceptors, even though the brain processes pain information arriving from elsewhere. The scalp, meninges and some blood vessels are pain-sensitive, which explains how headaches can occur despite the insensitivity of brain tissue.
4. Which functions can the human brain perform: thinking, regulation of heartbeat, and maintenance of body balance?
[UPPSC Civil Services Preliminary, GS I (2016)]
- (A) Thinking only
- (B) Heartbeat regulation only
- (C) Balance only
- (D) All three functions
Answer: (D) All three functions
Explanation: Higher cerebral regions support thinking, brainstem centres influence cardiovascular activity, and cerebellar pathways coordinate balance. These functions are distributed across different anatomical areas. Consequently the brain handles conscious cognition as well as involuntary physiological regulation and motor coordination.
3. During embryonic development, the retina arises as an outgrowth of which brain region?
[RPSC RAS Preliminary (2015 re-examination of 2013)]
- (A) Mesencephalon
- (B) Diencephalon
- (C) Telencephalon
- (D) Pons
Answer: (B) Diencephalon
Explanation: The neural retina develops from the optic vesicle, which grows out of the embryonic diencephalon. The optic nerve is likewise related developmentally to central nervous tissue. This is why the retina is considered a specialised neural structure rather than an ordinary peripheral receptor sheet.
2. Which part of the human brain is chiefly linked with memory and higher intellectual functions?
[CGPSC Preliminary, General Studies (2013)]
- (A) Medulla oblongata
- (B) Cerebrum
- (C) Brain cavity
- (D) Cerebellum
Answer: (B) Cerebrum
Explanation: The cerebrum, including the cerebral cortex and associated networks, is central to learning, memory, reasoning and conscious perception. The hippocampus is particularly important for forming many kinds of new memories. The cerebellum chiefly coordinates movement and also contributes to some cognitive processes.
1. Which region of the human brain acts as a major control centre for swallowing and vomiting?
[UPSC Civil Services Preliminary, General Studies (2007)]
- (A) Cerebellum
- (B) Cerebrum
- (C) Medulla oblongata
- (D) Pons
Answer: (C) Medulla oblongata
Explanation: The medulla oblongata houses brainstem circuits that coordinate swallowing, vomiting and other protective reflexes. It also contributes to vital breathing and cardiovascular regulation. The cerebellum chiefly refines motor coordination, whereas the cerebrum supports higher conscious functions.
Prepared for competitive exam revision. The original wording and independently verified answer keys should be consulted for formal exam appeals.
