NCERT grounding
This subtopic sits in section 18.4 Central Neural System of NCERT Class 11 Biology, Chapter 18 (Neural Control and Coordination). The chapter establishes that the central neural system (CNS) consists of the brain and the spinal cord, and that the brain is the "central information processing organ" controlling voluntary movement, involuntary visceral activity, thermoregulation, hunger, thirst, circadian rhythms, endocrine activity and behaviour. NCERT explicitly partitions the brain into three regions — forebrain, midbrain and hindbrain — and identifies the three protective meninges that lie between the skull and the brain tissue.
"The human brain is well protected by the skull. Inside the skull, the brain is covered by cranial meninges consisting of an outer layer called dura mater, a very thin middle layer called arachnoid and an inner layer (which is in contact with the brain tissue) called pia mater."
NCERT Class 11 Biology · §18.4
Protection & coverings
The brain weighs roughly 1.3–1.4 kg in an adult and floats in a thin film of cerebrospinal fluid (CSF) inside the cranial cavity. Three nested layers of connective tissue — collectively termed the cranial meninges — separate brain tissue from the inner surface of the skull. NCERT identifies them from outside in as dura mater, arachnoid and pia mater. NIOS adds that the CSF circulates through four ventricles within the brain and through the central canal of the spinal cord, providing buoyancy, shock-absorption and a controlled chemical environment for neurons.
Order matters. From skull inward, the sequence is bone → dura mater → arachnoid → pia mater → brain tissue. NEET often inverts the order in distractors.
Dura mater
Outer, tough fibrous layer pressed against the inner surface of the skull.
Function: mechanical protection; anchors the brain to the cranial vault.
Arachnoid
Very thin, web-like middle layer; subarachnoid space holds cerebrospinal fluid.
Function: cushions the brain via the fluid layer it traps below it.
Pia mater
Innermost delicate layer, in direct contact with brain tissue and following every gyrus.
Function: carries fine blood vessels onto the cortical surface.
The three divisions
NCERT divides the brain into three regions on developmental and positional grounds: forebrain, midbrain and hindbrain. Each region houses specific structures with non-overlapping functions, and most NEET questions on brain structure boil down to mapping a structure to its parent division and to its function. The summary table below pre-loads the three-by-three lookup you will need for matching-type PYQs.
Figure 1. Sagittal schematic of the human brain. The forebrain (cerebrum, thalamus, hypothalamus) wraps the midbrain dorsally; the hindbrain (pons, cerebellum, medulla) sits below. Note the brain-stem bracket grouping midbrain + pons + medulla only.
Forebrain in detail
The forebrain consists of three structures: the cerebrum (with its limbic system and association cortex), the thalamus, and the hypothalamus. Cerebrum forms the major part of the human brain. A deep median cleft — the longitudinal fissure — divides it into two cerebral hemispheres, which remain connected by a thick tract of myelinated fibres called the corpus callosum. The outer layer of cells covering each hemisphere is the cerebral cortex; it is thrown into prominent folds (gyri) and grooves (sulci) that maximise surface area within the cranial vault.
Cerebral cortex and its lobes
The cerebral cortex is functionally subdivided into four lobes per hemisphere — frontal (motor planning and voluntary movement), parietal (somatosensory integration), temporal (audition, language) and occipital (vision). It contains motor areas, sensory areas and large regions that are neither clearly sensory nor motor in function. These intermediate regions are called association areas; NCERT credits them with intersensory associations, memory and communication.
Thalamus — the sensory relay
The cerebrum wraps around the thalamus, which is the major coordinating centre for sensory and motor signalling. Almost all ascending sensory pathways (except olfaction) synapse in the thalamus before being projected onto the cortex. NEET treats the thalamus as the canonical "sensory relay" — a one-word association you must lock in.
Hypothalamus — the homeostatic thermostat
The hypothalamus lies at the base of the thalamus. It contains a number of centres which control body temperature, the urge for eating and drinking. It also contains several groups of neurosecretory cells, which secrete hormones called hypothalamic hormones (releasing and inhibiting hormones for the anterior pituitary, plus oxytocin and vasopressin for the posterior pituitary). NEET 2019 directly asked which part of the brain is responsible for thermoregulation — answer: hypothalamus.
Limbic system — emotion and motivation
The inner parts of the cerebral hemispheres and a group of associated deep structures like the amygdala and hippocampus form a complex structure called the limbic lobe or limbic system. Along with the hypothalamus, the limbic system regulates sexual behaviour and the expression of emotional reactions such as excitement, pleasure, rage and fear, as well as motivation. NEET 2023 mapped this combination ("limbic system and hypothalamus") to those exact behaviours.
Midbrain in detail
The midbrain is the shortest of the three divisions and is positionally sandwiched between the thalamus/hypothalamus of the forebrain and the pons of the hindbrain. A narrow canal called the cerebral aqueduct passes through it, linking the third ventricle of the forebrain to the fourth ventricle of the hindbrain and carrying cerebrospinal fluid.
The dorsal portion of the midbrain consists mainly of four round swellings (lobes) collectively called the corpora quadrigemina. As the NCERT summary records, the midbrain "receives and integrates visual, tactile and auditory inputs" — the upper pair (superior colliculi, in the broader anatomical literature) handles visual reflexes and the lower pair (inferior colliculi) handles auditory reflexes; for NEET, the NCERT-level statement is sufficient.
Round swellings on the midbrain
The dorsal midbrain carries four lobes — the corpora quadrigemina. NEET distractors often substitute "two" or attach the term to the cerebellum; the count and the location are both fair game.
Hindbrain in detail
The hindbrain comprises three structures: pons, cerebellum and medulla oblongata. The pons consists of fibre tracts that interconnect different regions of the brain — it functions chiefly as a relay. The cerebellum has a very convoluted surface, thrown into closely packed folia, in order to provide additional space for many more neurons; this maximises the wiring density needed to coordinate posture, balance and fine motor movement. The medulla connects the brain to the spinal cord; it contains centres that control respiration, cardiovascular reflexes and gastric secretions.
Pons
Relay
fibre tracts
- Connects different regions of the brain.
- NIOS: also helps regulate respiration along with the medulla.
- NEET 2024 paired Pons with "connects different regions of the brain".
Cerebellum & Medulla
Coordinate · Sustain
balance / vital reflexes
- Cerebellum — coordination, posture, balance; convoluted to pack neurons.
- Medulla — respiration, cardiovascular reflexes, gastric secretions.
- Medulla also harbours the cardiac control centre (NEET 2025).
Figure 2. Concentric protection of the human brain — bony skull, then dura mater, arachnoid (with CSF in the subarachnoid space), pia mater, then brain tissue. Memorise this outside-in order.
Grey vs white matter
The cerebral hemisphere shows two visibly distinct tissue zones. The outer cerebral cortex is referred to as grey matter due to its greyish appearance — the neuron cell bodies are concentrated here and impart that colour. Underneath the cortex lies the white matter, formed by the fibre tracts whose axons are wrapped in myelin sheath; the myelin gives an opaque white appearance. The same dichotomy is reversed in the spinal cord (grey matter lies inside, white matter outside), but NEET typically tests only the cerebrum version of this rule.
Brain stem
Three major regions make up the brain stem: midbrain, pons and medulla oblongata. The brain stem forms the connection between the brain and the spinal cord, and carries all ascending and descending fibre tracts between them. NCERT is explicit that the cerebrum is not part of the brain stem — a trap NEET 2024 weaponised by inserting "cerebrum" in place of "midbrain" in Statement II of a two-statement question.
Brain stem — top to bottom
-
Top
Midbrain
Corpora quadrigemina (4 lobes); cerebral aqueduct passes through.
Visual · tactile · auditory integration -
Mid
Pons
Fibre tracts that interconnect different regions of the brain.
Relay station -
Bottom
Medulla oblongata
Centres controlling respiration, cardiovascular reflexes, gastric secretions.
Vital reflexes -
Exit
Spinal cord
Continuation of the medulla; second CNS organ.
Cord begins
Worked examples
List the cranial meninges in the correct order from the skull inward, and name the layer that contains cerebrospinal fluid in the subarachnoid space.
Answer. From skull inward: dura mater (outer) → arachnoid (middle) → pia mater (inner). The cerebrospinal fluid lies in the subarachnoid space — that is, beneath the arachnoid layer, between arachnoid and pia mater. The pia mater itself is in direct contact with brain tissue.
Match each structure with the brain division it belongs to: (a) Corpus callosum, (b) Corpora quadrigemina, (c) Medulla oblongata, (d) Hypothalamus.
Answer. (a) corpus callosum — forebrain (connects the two cerebral hemispheres). (b) corpora quadrigemina — midbrain (four dorsal lobes). (c) medulla oblongata — hindbrain (also part of the brain stem). (d) hypothalamus — forebrain (at the base of the thalamus).
A patient has lost the centres that regulate respiration and heart rate, but voluntary movement and emotion are intact. Which brain region is damaged, and why are the others spared?
Answer. The damaged region is the medulla oblongata, which houses the respiratory and cardiovascular control centres. Voluntary movement is governed by the motor cortex of the cerebrum (forebrain) and emotion by the limbic system and hypothalamus — both forebrain structures lying anatomically far from the medulla, hence unaffected by an isolated medullary lesion.
Why is the cerebral cortex called grey matter while the inner part of the cerebral hemisphere is called white matter?
Answer. The cortex contains neuron cell bodies at high density, giving the tissue a greyish hue — hence grey matter. The inner part is dominated by myelinated axonal tracts; the lipid-rich myelin sheath renders the tissue opaque white — hence white matter.