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Master Nervous System for NEET 2026 with comprehensive notes on neuron structure, nerve impulse, brain anatomy, and reflex action. NCERT-aligned content with diagrams and PYQs.
Remember these points for your NEET preparation
Neural Control and Coordination is one of the most important and high-weightage chapters, contributing 5-7 questions in NEET annually. This comprehensive guide covers all NCERT concepts.
Definition: The system that controls and coordinates body activities through rapid electrical signals.
Central Nervous System (CNS):
Peripheral Nervous System (PNS):
Three Main Parts:
| Feature | Myelinated | Unmyelinated |
|---|---|---|
| Myelin | Present | Absent |
| Nodes of Ranvier | Present | Absent |
| Conduction | Saltatory (faster) | Continuous (slower) |
| Speed | 100-120 m/s | 0.5-2 m/s |
| Location | White matter, PNS | Gray matter |
Myelin in CNS: Oligodendrocytes Myelin in PNS: Schwann cells
| Type | Structure | Function |
|---|---|---|
| Sensory (Afferent) | Long dendrite, short axon | Carry impulse to CNS |
| Motor (Efferent) | Short dendrite, long axon | Carry impulse from CNS |
| Interneurons | Short processes | Connect neurons within CNS |
| Based on Processes | Number of Processes |
|---|---|
| Unipolar | 1 (axon only) |
| Bipolar | 2 (1 dendrite, 1 axon) |
| Multipolar | 3+ (many dendrites, 1 axon) |
Value: -70 mV (inside negative relative to outside)
Maintenance:
Stimulus → Threshold (-55 mV) → Action Potential
| Phase | Events | Potential |
|---|---|---|
| Resting | Na⁺/K⁺ pump maintains gradient | -70 mV |
| Depolarization | Na⁺ channels open, Na⁺ rushes in | -70 → +30 mV |
| Repolarization | Na⁺ channels close, K⁺ channels open | +30 → -70 mV |
| Hyperpolarization | K⁺ channels slow to close | Below -70 mV |
| Return to resting | Na⁺/K⁺ pump restores gradient | -70 mV |
All-or-None Law: Action potential either occurs fully or not at all; no partial response.
Refractory Period:
| Type | Mechanism | Speed |
|---|---|---|
| Continuous | Sequential depolarization | Slower |
| Saltatory | Jumps between Nodes of Ranvier | Faster |
Definition: Junction between two neurons where signal transmission occurs.
| Type | Mechanism | Speed |
|---|---|---|
| Electrical | Gap junctions, direct ion flow | Very fast |
| Chemical | Neurotransmitter release | Slower |
| Neurotransmitter | Location | Effect |
|---|---|---|
| Acetylcholine | NMJ, brain | Excitatory/Inhibitory |
| Norepinephrine | Sympathetic NS | Excitatory |
| Dopamine | Brain | Pleasure, movement |
| Serotonin | Brain | Mood, sleep |
| GABA | Brain | Inhibitory |
| Glutamate | Brain | Excitatory |
Weight: ~1400 g Protection: Skull, meninges, CSF
| Layer | Location | Characteristics |
|---|---|---|
| Dura mater | Outermost | Tough, fibrous |
| Arachnoid | Middle | Web-like, CSF beneath |
| Pia mater | Innermost | Delicate, on brain surface |
CSF (Cerebrospinal Fluid):
A. Cerebrum (Largest Part - 80%)
| Lobe | Location | Function |
|---|---|---|
| Frontal | Front | Motor control, thinking, speech (Broca's area) |
| Parietal | Top | Sensory processing, spatial awareness |
| Temporal | Side | Hearing, memory, speech comprehension (Wernicke's area) |
| Occipital | Back | Vision |
Cerebral Cortex:
Association Areas:
B. Thalamus
C. Hypothalamus
D. Limbic System
A. Cerebellum (Little Brain)
B. Pons
C. Medulla Oblongata
Brain Stem: Midbrain + Pons + Medulla
Location: Within vertebral column Length: ~45 cm Structure:
Functions:
| Number | Name | Type | Function |
|---|---|---|---|
| I | Olfactory | Sensory | Smell |
| II | Optic | Sensory | Vision |
| III | Oculomotor | Motor | Eye movement |
| IV | Trochlear | Motor | Eye movement |
| V | Trigeminal | Mixed | Face sensation, chewing |
| VI | Abducens | Motor | Eye movement |
| VII | Facial | Mixed | Facial expression, taste |
| VIII | Vestibulocochlear | Sensory | Hearing, balance |
| IX | Glossopharyngeal | Mixed | Taste, swallowing |
| X | Vagus | Mixed | Visceral organs |
| XI | Accessory | Motor | Neck muscles |
| XII | Hypoglossal | Motor | Tongue movement |
Mnemonic: On Old Olympus Towering Tops, A Finn And German Viewed Some Hops
| Region | Number |
|---|---|
| Cervical | 8 |
| Thoracic | 12 |
| Lumbar | 5 |
| Sacral | 5 |
| Coccygeal | 1 |
| Feature | Sympathetic | Parasympathetic |
|---|---|---|
| Origin | Thoracolumbar | Craniosacral |
| Ganglion location | Close to spinal cord | Near/in target organ |
| Neurotransmitter | Norepinephrine | Acetylcholine |
| General effect | Fight or flight | Rest and digest |
| Pupil | Dilates | Constricts |
| Heart rate | Increases | Decreases |
| Digestion | Inhibits | Stimulates |
| Bronchi | Dilates | Constricts |
Definition: Automatic, involuntary response to a stimulus.
Components (in order):
| Type | Example | Integration Center |
|---|---|---|
| Spinal | Knee jerk, withdrawal | Spinal cord |
| Cranial | Pupillary reflex | Brain |
| Conditional | Salivation to bell (Pavlov) | Brain |
| Unconditional | Salivation to food | Brain |
Structure:
Photoreceptors:
| Type | Shape | Pigment | Function | Sensitivity |
|---|---|---|---|---|
| Rods | Rod-shaped | Rhodopsin | Dim light, peripheral vision | High |
| Cones | Cone-shaped | Photopsins | Color, bright light, acuity | Low |
Fovea: Maximum cone density, sharpest vision Blind spot: Where optic nerve exits, no receptors
Three Parts:
| Part | Structures | Function |
|---|---|---|
| Outer ear | Pinna, ear canal, tympanic membrane | Sound collection |
| Middle ear | Malleus, Incus, Stapes | Sound amplification |
| Inner ear | Cochlea, vestibular apparatus | Hearing, balance |
Organ of Corti: Contains hair cells (auditory receptors) in cochlea
Q1 (NEET 2023): Resting membrane potential of neuron is:
Q2 (NEET 2022): The part of brain responsible for balance is:
Q3 (NEET 2021): Saltatory conduction occurs in:
Q4 (NEET 2020): Hypothalamus controls:
Q5 (NEET 2019): Which neurotransmitter is released at neuromuscular junction?
Q: Why is the resting potential negative? A: The Na⁺/K⁺ pump creates an ionic gradient (3 Na⁺ out, 2 K⁺ in). Additionally, K⁺ leak channels allow K⁺ to diffuse out, leaving the inside more negative relative to outside.
Q: What is the advantage of saltatory conduction? A: In myelinated neurons, action potential jumps between Nodes of Ranvier instead of traveling continuously. This is faster (100 m/s vs 1 m/s) and more energy-efficient.
Q: Why is the cerebellum called the "little brain"? A: It has a similar folded structure to the cerebrum but is smaller. Despite being only 10% of brain volume, it contains more neurons than the rest of the brain combined.
Q: What happens if the corpus callosum is cut? A: This procedure (commissurotomy) prevents communication between hemispheres. Patients can function normally in daily life but show "split-brain" effects in specific tests.
Q: Why does Parkinson's disease cause tremors? A: Parkinson's involves death of dopamine-producing neurons in the substantia nigra. Dopamine is essential for smooth, coordinated movements, so its deficiency causes tremors and rigidity.
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