Complete Nervous System Notes for NEET | Detailed Explanation with Diagram

🧠 Complete Nervous System Notes (Detailed & Easy Explanation)

The Nervous System is the master controlling and coordinating system of the human body. It regulates voluntary actions, involuntary actions, thinking, memory, emotions, reflexes, and homeostasis.

1. Overview of Nervous System

The nervous system is responsible for detecting stimuli, transmitting signals, processing information, and coordinating responses. It works through specialized cells called neurons.

Main Functions:

Control and coordination of body activities
Sensory perception
Memory and intelligence
Regulation of internal organs
Maintaining homeostasis

Labelled Nervous System Diagram (NEET + School Students)

2. Divisions of Nervous System

A. Central Nervous System (CNS)

Includes Brain and Spinal Cord. It acts as the control center.

B. Peripheral Nervous System (PNS)

Includes cranial nerves and spinal nerves that connect CNS to the body.

C. Autonomic Nervous System (ANS)

Sympathetic Nervous System – Fight or Flight
Parasympathetic Nervous System – Rest and Digest

3. Structure of Neuron

Neuron is the structural and functional unit of nervous system.

Parts of Neuron:

Dendrites – Receive impulses
Cell Body (Cyton) – Contains nucleus
Axon – Transmits impulses
Myelin Sheath – Increases speed of conduction
Nodes of Ranvier – Gaps in myelin sheath

Saltatory Conduction: Impulse jumps from one node to another, increasing speed.

4. Types of Neurons

Type	Function
Sensory Neuron	Carry impulses from receptor to CNS
Motor Neuron	Carry impulses from CNS to effector
Interneuron	Connect neurons within CNS

5. Brain (Detailed Study)

Forebrain

Cerebrum – Largest part, controls intelligence, thinking, memory
Thalamus – Sensory relay station
Hypothalamus – Controls temperature, hunger, thirst, hormones

Midbrain

Controls visual and auditory reflexes.

Hindbrain

Cerebellum – Balance and posture
Pons – Connects brain parts
Medulla Oblongata – Controls heartbeat, breathing

6. Spinal Cord

It is a cylindrical structure extending from medulla to lumbar region.

Functions:

Conducts impulses to and from brain
Controls reflex actions

7. Reflex Action & Reflex Arc

Reflex action is a rapid, automatic response to a stimulus.

Pathway:
Receptor → Sensory Neuron → Spinal Cord → Motor Neuron → Effector

8. Synapse & Impulse Transmission

Synapse is the junction between two neurons.

Types of Synapse:

Electrical Synapse
Chemical Synapse (Neurotransmitters like Acetylcholine)

9. Autonomic Nervous System in Detail

Sympathetic	Parasympathetic
Increases heart rate	Decreases heart rate
Dilates pupil	Constrics pupil
Inhibits digestion	Stimulates digestion

10. Protective Coverings of Brain

Meninges – Dura mater, Arachnoid mater, Pia mater
Cerebrospinal Fluid (CSF)

11. Disorders of Nervous System

Alzheimer’s Disease – Memory loss
Parkinson’s Disease – Tremors
Epilepsy – Seizures
Multiple Sclerosis – Myelin damage

12. Quick Revision Summary

• CNS = Brain + Spinal Cord

• Neuron is functional unit

• 12 Cranial nerves

• Reflex arc has 5 components

• Sympathetic = Fight or Flight

• Parasympathetic = Rest and Digest

Conclusion

The nervous system is a complex but highly organized system responsible for control, coordination, memory, reflexes, and survival. Understanding neuron structure, brain divisions, reflex arc, and autonomic regulation is essential for competitive exams like NEET.

Complete Nervous System Notes for NEET 2026 – Structure, Functions, Brain, Reflex Arc & Autonomic System Explained