Human Nervous System Notes for SSC CGL, CHSL and Railways

Human Nervous System Notes for SSC CGL, CHSL and Railways

1. Nervous System (Central, Peripheral, Autonomic)

  • The functioning of the nervous system depends on detecting a stimulus in the internal or external environment and responding to it.
  • Neuron (Sensory, Motor, Association/Connecting): basic unit of nervous system.
  • After birth there is no cell division of nerves in humans.
  • The biological death of a patient means the death of the tissues of the Brain.
  • The aquatic animal with the most developed intelligence is Shark.

Classification of Nervous System

Table of Contents

  1. CNS
    1. Brain
    2. Spinal Cord
  2. PNS
  3. ANS
  4. Neurons

1.1 Central Nervous System (Brain + Spinal Cord)

It controls whole body and the nervous system.

The meninges refer to the membranous coverings of the brain and spinal cord. There are three layers of meninges

  • The Outer membrane: Dura mater
  • The Middle membrane: Arachnoid membrane
  • The Inner membrane: Pia mater

1.1.1 Brain (Fore-Brain, Mid-Brain, Hind-Brain)

The human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system.

parts of brain

  • It is covered by a bony box called cranium which protects it from injuries.
  • The brain consists of the cerebrum, the brainstem and the cerebellum.
  • It controls most of the activities of the body, processing, integrating, and coordinating the information it receives from the sense organs, and making decisions as to the instructions sent to the rest of the body.
  • The adult human brain weighs about 3 pounds (1,300-1,400 g).
  • The cerebrum is the largest part of the human brain.
  • EEG(Electroencephalogram) records the activity of Brain.

1.1.1 (A) Fore Brain (Cerebrum + Thalamus + Hypothalamus)

  • Cerebrum is the center if wisdom, memory, will-power, movements, knowledge and thinking.
  • Thalamus is the center of pain, cold and heat.
  • Hypothalamus controls the hormonal secretion of endocrine glands, BP, sweat, anger, joy, thirst, hunger, etc.

1.1.1 (B) Mid Brain

Center of vision and hearing power

1.1.1 (C) Hind Brain (Cerebellum[Latin for “little brain”] + Pons[Latin for “bridge”] + Medulla oblongata)

  • Cerebellum maintains the body posture of human being.
  • Pons acts as a bridge between the brain and the spinal cord.
  • Medulla controls activities of internal organs like heart action, respiration, coughing, sneezing, etc.

1.1.2 Spinal Cord

The spinal cord extends from the medulla oblongata and continues downwards and lies within the neural canal of the vertebral column or backbone.

  • It controls the reflexes(reflex actions) below the neck.
  • It also controls the sensory impulses from the skin and muscles to the brain.
  • Vertebrae of the vertebral column protect spinal cord from injuries.
  • It conducts the motor responses from the brain to the muscles of the trunk and limbs.

1.2 Peripheral Nervous System

Made up of nerves arising from brain and spinal cord.
There are 12 pairs of cranical nerves and 31 pairs of spinal nerves.

1.3 Autonomic Nervous System

Consists of two sets of motor neurons and a collection of ganglia.

  • It supplies nerves to all the internal organs and blood vessel of the body.
  • Hair gets erected by its action.
  • It increases the RBC, rate of respiration, BP and blood sugar in the body.

Neurons(Axon + Dendrite + Cell Body)

Neurons are the core components of the brain and spinal cord of the central nervous system (CNS).
Parts of Neuron

Functions of the three parts of a neuron

  • Axon: It conducts messages away from the cell body.
  • Dendrite: It receives information from axon of another cell and conducts the messages towards the cell body.
  • Cell body: It contains nucleus, mitochondria, and other organelles. It is mainly concerned with the maintenance and growth.


It is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron.

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