Nervous System

The nervous system is the body’s control and communication network. It is made of special cells called neurons, which transmit signals throughout the body. These signals allow the body to respond to changes in the environment, coordinate movements, and control vital functions like breathing and heartbeat.

In simple animals like jellyfish, it is just a basic net, while crabs have two nerve centers. In humans, it is highly developed and capable of controlling complex actions, thoughts, emotions, and much more.

Human nervous system depicting CNS and PNS

Parts of the Human Nervous System

The nervous system has two parts: the central and peripheral nervous systems.

Central Nervous System

The Central Nervous System consists of the brain and the spinal cord. It works as a center that controls the whole body.

Brain

The brain functions to think, learn, memorize, and make decisions. The main parts of the brain are:

The forebrain is composed of the cerebrum, thalamus, and hypothalamus. It controls thoughts, memory, and feelings.
The midbrain is a small part of the brain that connects the forebrain and hindbrain. It helps send messages between different brain parts.
The hindbrain includes the cerebellum, pons, and medulla. This part controls balance, movement, and breathing.

Spinal Cord

The spinal cord is a bundle of nerves inside the spine. It carries messages between the body and the brain. It helps control fast actions, like moving your hand away from hot objects.

Peripheral Nervous System

The Peripheral Nervous System consists of the nerves outside of the brain and spinal cord. It links them to all body parts. The PNS helps with both voluntary and automatic actions.

There are two kinds of nerves in the PNS:

Afferent nerves: They carry messages from the body to the brain.
Efferent nerves: They carry messages from the brain to the body.

Divisions of the PNS

PNS is further divided into the somatic and autonomic nervous systems. The somatic nervous system helps you control your body’s movements, like walking, talking, and writing. The autonomic nervous system manages automatic body functions like digestion and heartbeat.

The autonomic system has two parts.

Sympathetic System: It prepares your body to fight or run away from danger.
Parasympathetic System: It helps your body calm down and relax.

Neuron

The neuron is the main cell that carries messages in the nervous system. It has three parts:

Dendrites are short branches that take messages from others.
The Cell Body has the nucleus and manages the cell.
Axon is a long thread that transmits the message from a neuron’s cell body to the target.
There is a small gap called a synapse at the axon’s end. Messages jump across this gap.

Alt-text: Neuron

Nerves

Nerves are bundles of neurons grouped together. They carry messages between the brain, spinal cord, and body parts.

There are three types of nerves.

Sensory Nerves: They carry signals from sense organs to the brain.
Motor Nerves: They send signals from the brain to the muscles.
Mixed Nerves: They carry both sensory and motor signals.

Cranial and Spinal Nerves

Cranial nerves start from the brain and control the head and neck. The Spinal nerves start from the spinal cord and control the rest of the body. These nerves are part of the PNS and connect directly with the CNS.

Summary

The nervous system sends signals, to and fro, through the neurons. It has two main parts: CNS (brain and spinal cord) and PNS (all other nerves). This system helps control actions we do and things our body does by itself. Neurons and nerves make sure the brain and body work together.

Frequently Asked Questions

Q1. What are the diseases associated with the nervous system?

A. Diseases of the nervous system include Alzheimer’s, Parkinson’s, epilepsy, stroke, and multiple sclerosis. They affect memory, movement, communication, or overall brain–body coordination.

Q2. What is the importance of the myelin sheath?

A. The myelin sheath insulates the axon, allowing nerve impulses to travel quickly and efficiently. It also protects the axon and prevents signal loss during transmission.

Q3. How does the nervous system save energy during rest?

A: The parasympathetic system slows down heart rate and conserves energy when the body is calm.

Q4. Why does the nervous system need both electrical and chemical signals?

A: Electrical signals move quickly within neurons, while chemical signals help neurons talk to each other at synapses.

Q5. What are reflex actions?

Reflex actions are quick, automatic responses to stimuli that occur without conscious thought. They help the body protect itself from harm, like pulling your hand away from something hot.