40. What is the usual direction of impulse transmission through the main parts of a neuron?
[SSC CHSL Tier I (30 Nov 2025, Shift 2)]
- (A) Dendrite → cell body → axon
- (B) Axon → dendrite → cell body
- (C) Cell body → dendrite → receptor
- (D) Synaptic cleft → muscle → dendrite
Answer: (A) Dendrite → cell body → axon
Explanation: Dendrites commonly receive synaptic input, the cell body integrates information, and an action potential travels along the axon toward its terminals. At chemical synapses, neurotransmitter release permits signalling onward. This arrangement explains functional polarity in a typical neuron.
39. Which brain structure ensures precise voluntary movements while maintaining posture and balance?
[SSC CHSL Tier I (27 Nov 2025, Shift 2)]
- (A) Cerebrum
- (B) Cerebellum
- (C) Medulla
- (D) Hypothalamus
Answer: (B) Cerebellum
Explanation: The cerebellum compares intended movements with sensory feedback and refines timing, force and coordination. Its activity supports gait, posture and equilibrium. It does not simply initiate conscious thought; those higher functions are associated more strongly with the cerebral cortex.
38. Consider these structures:
I. Heart;
II. Spinal cord.
Which belongs to the central nervous system?
[SSC CHSL Tier I (14 Nov 2025, Shift 3)]
- (A) Only I
- (B) Only II
- (C) Both I and II
- (D) Neither I nor II
Answer: (B) Only II
Explanation: The central nervous system comprises the brain and spinal cord. The spinal cord relays nerve impulses and processes many reflexes. The heart is a muscular organ of the circulatory system, although nerves of the autonomic system influence its rhythm.
37. Which brain region contains the main biological clock controlling circadian rhythms?
[SSC CGL Tier I (15 Sep 2025, Shift 3)]
- (A) Cerebellum
- (B) Hypothalamus
- (C) Medulla oblongata
- (D) Thalamus
Answer: (B) Hypothalamus
Explanation: The suprachiasmatic nucleus of the hypothalamus is the master circadian pacemaker. It receives light-related information through retinal pathways and helps synchronise sleep, hormones and other daily rhythms. The cerebellum is more concerned with coordination, while the medulla regulates essential autonomic functions.
36. Which is the correct conventional division of the human brain?
[UPSC CDS II, General Knowledge (14 Sep 2025)]
- (A) Forefront, standard and hindbrain
- (B) Forebrain, median and rear brain
- (C) Forebrain, midbrain and hindbrain
- (D) Precursor, mean and hindbrain
Answer: (C) Forebrain, midbrain and hindbrain
Explanation: For general biology, the human brain is grouped into forebrain, midbrain and hindbrain. The forebrain supports complex processing and homeostasis; the midbrain is involved in sensory and motor pathways; the hindbrain includes cerebellum, pons and medulla.
35. Which group of activities is most characteristically controlled by the hindbrain?
[UPSC NDA II, General Ability Test (14 Sep 2025)]
- (A) Involuntary responses such as salivation and vomiting
- (B) Conscious interpretation of every sensory impulse
- (C) Initiation of all deliberate thought
- (D) Awareness of hunger and satiety alone
Answer: (A) Involuntary responses such as salivation and vomiting
Explanation: The hindbrain contains the medulla, pons and cerebellum. Medullary centres control essential automatic reflexes such as vomiting and aspects of salivation and blood-pressure regulation. Balance is coordinated by the cerebellum, whereas hunger and satiety depend strongly on hypothalamic circuits.
34. Which amino acid is a biochemical precursor of the neurotransmitter serotonin?
[SSC CGL 2024 Tier II (20 Jan 2025)]
- (A) Tryptophan
- (B) Isoleucine
- (C) Valine
- (D) Methionine
Answer: (A) Tryptophan
Explanation: Serotonin, also called 5-hydroxytryptamine, is synthesised from the essential amino acid tryptophan. The pathway involves hydroxylation followed by decarboxylation. Serotonin participates in mood, appetite and sleep-related signalling, although those processes also depend on multiple other transmitters.
33. Cranial and spinal nerves together mainly form which nervous-system division?
[RRB Technician Grade III (28 Dec 2024, Shift 3)]
- (A) Peripheral nervous system
- (B) Central nervous system
- (C) Endocrine system
- (D) Digestive nervous system
Answer: (A) Peripheral nervous system
Explanation: Cranial and spinal nerves connect the brain and spinal cord to the remaining body, and thus belong to the peripheral nervous system. By contrast, the brain and spinal cord form the central nervous system, which integrates incoming information and coordinates responses.
32. Which of these is generally recognised as the longest type of cell in the human body?
[RRB ALP CBT I (27 Nov 2024, Shift 2)]
- (A) Nerve cell
- (B) Ovum
- (C) Red blood cell
- (D) Fat cell
Answer: (A) Nerve cell
Explanation: Some neurons possess axons extending from the spinal cord to distant muscles, potentially over a metre in an adult. That makes nerve cells notable for their length. The ovum is particularly large in diameter, but it is not the longest cell.
31. In which part of the nervous system are many common withdrawal-reflex arcs organised?
[RRB ALP CBT I (26 Nov 2024, Shift 3)]
- (A) Medulla
- (B) Forebrain
- (C) Spinal cord
- (D) Cerebellum
Answer: (C) Spinal cord
Explanation: The spinal cord contains local neural circuits that can coordinate rapid protective reflexes, such as pulling a hand away from heat. Sensory information enters through dorsal pathways and motor output exits through ventral pathways. The brain is informed but need not act first.
