Neural Control and Coordination - Complete NEET Biology Notes 2026

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.

Introduction to Neural System

Definition: The system that controls and coordinates body activities through rapid electrical signals.

Organization of Neural System

Central Nervous System (CNS):

• Brain
• Spinal cord

Peripheral Nervous System (PNS):

• Cranial nerves (12 pairs)
• Spinal nerves (31 pairs)

Neuron - Structural and Functional Unit

Structure of Neuron

Three Main Parts:

1. Cell Body (Soma/Cyton)

• Contains nucleus and most organelles
• Nissl granules (rough ER) - protein synthesis
• Site of metabolic activity

2. Dendrites

• Short, branched processes
• Receive signals from other neurons
• Conduct impulse toward cell body

3. Axon

• Single, long process
• Conducts impulse away from cell body
• May be myelinated or unmyelinated
• Ends in terminal buttons (synaptic knobs)

Myelin Sheath

Myelin in CNS: Oligodendrocytes Myelin in PNS: Schwann cells

Types of Neurons

Nerve Impulse

Resting Membrane Potential

Value: -70 mV (inside negative relative to outside)

Maintenance:

• Na⁺/K⁺ ATPase pump: 3 Na⁺ out, 2 K⁺ in
• High K⁺ inside, High Na⁺ outside
• K⁺ leak channels maintain negativity

Generation of Action Potential

Stimulus → Threshold (-55 mV) → Action Potential

Properties of Action Potential

All-or-None Law: Action potential either occurs fully or not at all; no partial response.

Refractory Period:

• Absolute: No stimulus can generate another AP
• Relative: Only strong stimulus can generate AP

Conduction of Nerve Impulse

Synapse

Definition: Junction between two neurons where signal transmission occurs.

Types of Synapses

Structure of Chemical Synapse

1. Presynaptic terminal: Contains synaptic vesicles with neurotransmitters
2. Synaptic cleft: 20-40 nm gap
3. Postsynaptic membrane: Contains receptors

Synaptic Transmission

1. Action potential reaches axon terminal
2. Ca²⁺ channels open, Ca²⁺ enters
3. Synaptic vesicles fuse with membrane
4. Neurotransmitter released into synaptic cleft
5. NT binds to receptors on postsynaptic membrane
6. Ion channels open/close on postsynaptic neuron
7. NT removed (reuptake, enzyme degradation, diffusion)

Common Neurotransmitters

Central Nervous System

Brain

Weight: ~1400 g Protection: Skull, meninges, CSF

Meninges (Three Layers)

CSF (Cerebrospinal Fluid):

• Volume: ~150 mL
• Functions: Protection, nutrient supply, waste removal

Parts of Brain

1. Forebrain

A. Cerebrum (Largest Part - 80%)

Cerebral Cortex:

• Gray matter on surface (6 layers)
• White matter inside (myelinated fibers)
• Corpus callosum connects two hemispheres

Association Areas:

• Higher mental functions
• Memory, reasoning, judgment

B. Thalamus

• Relay center for sensory information
• All sensory signals (except smell) pass through

C. Hypothalamus

• Controls autonomic functions
• Regulates: Temperature, hunger, thirst, sleep, emotions
• Controls pituitary gland (master of master gland)

D. Limbic System

• Hippocampus: Memory formation
• Amygdala: Emotions, especially fear

2. Midbrain

• Contains cerebral peduncles
• Superior colliculi: Visual reflexes
• Inferior colliculi: Auditory reflexes
• Contains substantia nigra (dopamine, Parkinson's disease)

3. Hindbrain

A. Cerebellum (Little Brain)

• Second largest part
• Coordination of voluntary movements
• Balance and posture
• Motor learning

B. Pons

• Relay center between cerebrum and cerebellum
• Contains pneumotaxic center (breathing)

C. Medulla Oblongata

• Controls vital functions: Breathing, heart rate, blood pressure
• Contains reflex centers: Vomiting, swallowing, coughing, sneezing

Brain Stem: Midbrain + Pons + Medulla

Spinal Cord

Location: Within vertebral column Length: ~45 cm Structure:

• Gray matter (H-shaped) inside
• White matter outside (opposite of brain)

Functions:

• Conducts impulses between brain and body
• Center for spinal reflexes

Peripheral Nervous System

Cranial Nerves (12 pairs)

Mnemonic: On Old Olympus Towering Tops, A Finn And German Viewed Some Hops

Spinal Nerves (31 pairs)

Autonomic Nervous System (ANS)

Reflex Action

Definition: Automatic, involuntary response to a stimulus.

Reflex Arc

Components (in order):

1. Receptor: Detects stimulus
2. Sensory (afferent) neuron: Carries impulse to CNS
3. Integration center: Interneuron in spinal cord
4. Motor (efferent) neuron: Carries impulse to effector
5. Effector: Muscle or gland that responds

Types of Reflexes

Sensory Reception

Eye - Photoreception

Structure:

• Sclera (white), Cornea (transparent front)
• Choroid (vascular), Iris (colored, controls pupil)
• Retina (photoreceptors)

Photoreceptors:

Fovea: Maximum cone density, sharpest vision Blind spot: Where optic nerve exits, no receptors

Ear - Hearing and Balance

Three Parts:

Organ of Corti: Contains hair cells (auditory receptors) in cochlea

Previous Year NEET Questions

Q1 (NEET 2023): Resting membrane potential of neuron is:

• (a) +70 mV
• (b) -70 mV ✓
• (c) +30 mV
• (d) -30 mV

Q2 (NEET 2022): The part of brain responsible for balance is:

• (a) Cerebrum
• (b) Cerebellum ✓
• (c) Medulla
• (d) Hypothalamus

Q3 (NEET 2021): Saltatory conduction occurs in:

• (a) Unmyelinated neurons
• (b) Myelinated neurons ✓
• (c) All neurons
• (d) Dendrites only

Q4 (NEET 2020): Hypothalamus controls:

• (a) Body temperature ✓
• (b) Voluntary movements
• (c) Balance
• (d) Hearing

Q5 (NEET 2019): Which neurotransmitter is released at neuromuscular junction?

• (a) GABA
• (b) Dopamine
• (c) Acetylcholine ✓
• (d) Serotonin

Quick Revision Points

1. Functional unit: Neuron
2. Resting potential: -70 mV
3. Action potential peak: +30 mV
4. Myelination in CNS: Oligodendrocytes
5. Myelination in PNS: Schwann cells
6. Largest brain part: Cerebrum
7. Second largest: Cerebellum
8. Master of master gland: Hypothalamus
9. Relay center: Thalamus
10. Memory formation: Hippocampus
11. Vital functions: Medulla oblongata
12. Fight or flight: Sympathetic NS
13. Rest and digest: Parasympathetic NS
14. Number of cranial nerves: 12 pairs
15. Number of spinal nerves: 31 pairs

FAQs

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.

Brain regions and their functions running together?

Cerebrum, cerebellum, hypothalamus, medulla — each has a distinct function NEET expects you to attach correctly, not just recognise by name. Message us on WhatsApp at +91 88264 44334 with the brain region you keep confusing, and we'll send a function-only reference built the way NEET phrases these questions.

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