Animals Nervous System: Classification, Parts, Functions and Examples

The animals nervous system is a specialised control and communication system that helps animals sense their surroundings, process information, and produce suitable responses. 

It plays an important role in coordinating movements, maintaining body functions, and supporting complex activities such as learning and memory. As animals differ in their level of organisation, their nervous systems also vary from simple nerve networks in basic organisms to advanced brains and spinal cords in complex animals. 

This article covers the structure, functions, types, neurons, reflex actions, and differences between vertebrate and invertebrate nervous systems. 

Table of Contents

• What is the Animals Nervous System
• Structure of the Animals Nervous System
• Types of Animals Nervous System
• 3 Major Divisions of the Animals Nervous System
• How does the Animals Nervous System Work
• Common Disorders of the Nervous System
• Nervous System in Vertebrates and Invertebrates
• Frequently Asked Questions on Animals Nervous System

What is the Animals Nervous System

The animals nervous system is a network of specialised cells and organs that receives information, processes it, and sends signals to different parts of the body. It acts as the body's communication and control system.

The nervous system helps animals to:

• Sense changes in the environment
• Coordinate body movements
• Control internal organs
• Maintain balance
• Respond to danger
• Learn and remember information

Without a nervous system, animals would not be able to move, react, or survive in changing surroundings.

Structure of the Animals Nervous System

The nervous system consists of organs and specialised nerve cells called neurons that work together for coordination and control.

The major components of the nervous system include the brain, spinal cord, nerves, sensory receptors, and neurons. Among these, neurons are the basic structural and functional units that carry electrical signals called nerve impulses throughout the body.

The main parts of a neuron are:

• Cell body: Contains the nucleus and controls neuron activities.
• Dendrites: Receive signals and carry them towards the cell body.
• Axon: Transmits nerve impulses away from the cell body.
• Axon terminals: Pass signals to other neurons, muscles, or glands.

Neurons help animals receive information, transmit nerve impulses, connect the brain with body organs, and coordinate responses.

Types of Animals Nervous System

Animals have different types of nervous systems based on their body complexity and level of organisation. 

While simple animals rely on basic nerve networks to detect and respond to changes, complex animals have specialised nervous systems with a brain and spinal cord for faster and more accurate coordination. 

Let us understand the different types of nervous systems found in animals.

1. Diffuse Nervous System

The simplest form of nervous system is the diffuse nervous system, where nerve cells are spread throughout the body in the form of a network. 

Since there is no central control centre, responses are simple and occur through signals travelling across the nerve network.

Found in:

• Hydra
• Jellyfish
• Other simple aquatic animals

Characteristics:

• Nerve cells are arranged as a network
• No brain or spinal cord is present
• Helps detect touch and environmental changes
• Produces simple responses to stimuli

2. Ladder-like Nervous System

As animals become more complex, their nervous systems become more organised. The ladder-like nervous system shows an early stage of centralisation, where nerve cords are arranged in a structured pattern.

Found in: Flatworms such as Planaria

Characteristics:

• Two main nerve cords run along the body
• Connected by transverse nerves, forming a ladder-like structure
• Provides better coordination than a diffuse nervous system
• Helps control body movements efficiently

3. Ganglionic Nervous System

Further development of the nervous system leads to the formation of ganglia, which are groups of nerve cells that act as control centres. These structures allow faster processing of information and improved movement control.

Found in:

• Earthworms
• Cockroaches
• Insects
• Other arthropods

Characteristics:

• Contains clusters of nerve cells called ganglia
• Ganglia are connected by nerve cords
• Provides faster responses and better coordination
• Controls different body segments

4. Centralised Nervous System

In higher animals, the nervous system becomes highly developed with a central brain and spinal cord. This centralised arrangement allows animals to perform complex activities such as learning, memory, and decision-making.

Found in:

• Fish
• Amphibians
• Reptiles
• Birds
• Mammals

Characteristics:

• The brain acts as the main control centre
• The spinal cord connects the brain with the body
• Controls complex body functions
• Enables quick responses and adaptation

Also Read: Diagram of Neuron

3 Major Divisions of the Animals Nervous System

As nervous systems become more advanced, they are divided into specialised parts that perform different functions. 

In complex animals, the nervous system mainly consists of the central nervous system, peripheral nervous system, and autonomic nervous system.

1. Central Nervous System (CNS)

The central nervous system acts as the command centre of the body. It receives information, processes signals, and sends instructions to different parts of the body.

Main Parts:

• Brain
• Spinal cord

Functions:

• Controls and coordinates body activities
• Processes information from sensory organs
• Regulates movement, thinking, learning, and memory
• Controls reflex actions

Found in: Vertebrates such as fish, amphibians, reptiles, birds, and mammals

2. Peripheral Nervous System (PNS)

While the CNS processes information, the peripheral nervous system helps in communication between the CNS and the rest of the body. It carries messages to and from muscles, organs, and sensory receptors.

Main Components:

• Cranial nerves
• Spinal nerves

Functions:

• Carries sensory information to the CNS
• Sends motor commands from the CNS to body parts
• Connects the brain and spinal cord with organs

Found in: Vertebrates, including mammals, birds, reptiles, amphibians, and fish

3. Autonomic Nervous System (ANS)

Some body activities occur automatically without conscious control. The autonomic nervous system regulates these involuntary functions and helps maintain internal balance.

Functions:

• Controls heartbeat
• Regulates digestion
• Maintains blood circulation
• Controls sweating and breathing

Found in: Vertebrates, including humans and other mammals

Here are the major divisions of the autonomic nervous system:

a. Sympathetic Nervous System

The sympathetic nervous system prepares the body to respond during stressful situations. It activates the body's emergency response system.

Functions:

• Increases heartbeat
• Dilates pupils
• Raises blood pressure
• Provides energy during emergencies

b. Parasympathetic Nervous System

After stressful conditions, the parasympathetic nervous system helps the body return to a relaxed state and maintain normal functions.

Functions:

• Slows heartbeat
• Promotes digestion
• Conserves energy
• Maintains body balance

c. Somatic Nervous System

The somatic nervous system controls voluntary actions by connecting the CNS with skeletal muscles. It allows animals to respond consciously to their surroundings.

Functions:

• Controls movements like walking, running, flying, and swimming
• Carries sensory information from skin and muscles
• Helps perform voluntary actions

Found in: Vertebrates, including humans and other mammals

d. Enteric Nervous System

Apart from controlling movement and responses, animals also need a system to regulate digestion. The enteric nervous system is a specialised network of nerves that manages digestive activities.

Functions:

• Controls movement of food through the digestive tract
• Regulates secretion of digestive juices
• Coordinates digestion

Found in: Vertebrates, especially mammals

Thus, the nervous system of animals ranges from simple nerve networks in basic organisms to highly specialised systems in complex animals.

Also Read: Vertebrates and Invertebrates

How does the Animals Nervous System Work

After understanding the different parts and types of the nervous system, the next step is to know how these components work together to help animals respond to stimuli. 

The nervous system follows a systematic pathway in which signals are received, processed, and converted into appropriate responses.

• The process begins when sensory receptors detect a stimulus such as light, sound, temperature, or touch from the surroundings.
• The detected information is carried by sensory neurons to the brain or spinal cord for processing.
• The brain or spinal cord analyses the information and decides the suitable response.
• Motor neurons then transmit signals from the brain or spinal cord to muscles or glands.
• The muscles or glands produce the final response, allowing the animal to react to the stimulus.

This coordinated process takes only fractions of a second, helping animals quickly respond to changes and maintain survival.

Common Disorders of the Nervous System 

The nervous system is essential for maintaining body coordination and control, but any damage or abnormal changes in its structure can affect normal functioning. Some major disorders that can impact the nervous system include:

Disorder	Description
Alzheimer's Disease	Causes memory loss due to the degeneration of brain cells
Parkinson's Disease	Affects movement, balance, and coordination
Epilepsy	Causes repeated seizures due to abnormal brain activity
Stroke	Occurs due to reduced or blocked blood supply to the brain
Meningitis	Infection and inflammation of the membranes covering the brain and spinal cord

Early diagnosis and proper medical treatment can help manage many nervous system disorders and prevent further complications.

Nervous System in Vertebrates and Invertebrates

The nervous system varies among animals based on their body structure and complexity. Vertebrates have a highly developed nervous system with a brain and spinal cord, while invertebrates have simpler arrangements such as nerve networks or ganglia.

Feature	Vertebrates	Invertebrates
Nervous System Structure	Well-developed brain and spinal cord	Simple nerve networks, cords, or ganglia
Backbone	Present	Absent
Sense Organs	Complex and highly developed	Simple and less developed
Coordination	Highly coordinated body functions	Simpler body coordination
Response	Faster and more complex responses	Basic responses to stimuli
Examples	Fish, amphibians, reptiles, birds, mammals	Hydra, jellyfish, earthworms, insects

So far, you have learnt that the animals nervous system helps animals sense their surroundings, coordinate body functions, and respond quickly to stimuli. From simple nerve nets to complex brains, it has evolved to support survival and adaptation.