The key difference between diffuse and centralized nervous system is that the diffuse nervous system is the most primitive form of the nervous system where nerve cells are typically distributed beneath the outer epidermal of an organism, while the centralized nervous system is a complex form of the nervous system where a large number of nerve cells are concentrated in the brain and spinal cord of an organism.
The nervous system is the main regulatory and communicating system in a body. Diffuse and centralized nervous systems are two types of nervous systems in animals. The diffuse nervous system is found in cnidarians (sea anemones) and ctenophores or comb jellies. The centralized nervous system is found in vertebrates like amphibians, reptiles, and mammals.
CONTENTS
1. Overview and Key Difference
2. What is a Diffuse Nervous System
3. What is a Centralized Nervous System
4. Similarities – Diffuse and Centralized Nervous System
5. Diffuse vs Centralized Nervous System in Tabular Form
6. Summary – Diffuse vs Centralized Nervous System
What is a Diffuse Nervous System?
The diffuse nervous system is a type of nervous system where nerve cells are equally distributed throughout the body, usually beneath the outer epidermal layer. Large concentrations of nerve cells are not centralized in this system. However, there are ganglia or small concentrations of neurons. Cnidarians, including corals, hydras, jellyfish, sea anemones, sea pens, sea whips and sea fans, have a diffuse nervous system. Moreover, members of phylum ctenophore have a diffuse nervous system. Ctenophores are also known as comb jellies, sea gooseberries, sea walnut or Venus’s girdles. As a matter of fact, the diffuse nervous system is a distinctive feature of marine invertebrates.
Figure 01: Nervous Systems
Most cnidarians like hydra have nerve nets. A nerve net is a mesh-like system of individual and separate nerve cells and fibres. The species of hydra have two nets. One is present in between the epidermis and musculature, while the second is located in the gastrodermis. The connections can take place between two nets at various points. The individual neurons make contact but do not fuse. Therefore, they form structures similar to synapses of vertebrates. Moreover, several differences may occur in diffuse nervous systems among these invertebrates.
What is a Centralized Nervous System?
A centralized nervous system is a complex form of the nervous system where a large amount of nerve cells is concentrated in the brain and the spinal cord. It occurs predominantly in all vertebrates. It also can be found in invertebrates such as arthropods, flatworms, annelids, mollusks, and cephalopods. The central nervous system consists of the brain and spinal cord in vertebrates. As it combines information of the entire body and coordinates activity, it is referred to as the central nervous system.
The brain is the most complex organ, and it has 100 billion neurons. It has four lobes: temporal, parietal, occipital and frontal. The spinal cord runs the full length of the back and carries information between brain and body. The brain and spinal cord are both covered with a protective membrane called meninges. Moreover, the central nervous system can be divided into two parts: white and gray matter. Both tissues are protected by glial cells. The outer cortex of the brain has gray matter, which consists of axons and oligodendrocytes (glial cells). The inner part of the brain has white matter, and it consists mainly of neurons.
Figure 02: Central Nervous System
In the higher vertebrate, there are around 12 pairs of cranial nerves that arise from the brain and pass through the holes of the skull rather than along the spinal cord. Cephalization is an evolutionary feature in which the mouth, sense organs, and nerve ganglia become concentrated at the front end that is producing a head region. This leads to the formation of sophisticated brains in three groups of animals, including arthropods, cephalopods mollusks and vertebrates.
What are the Similarities Between Diffuse and Centralized Nervous System?
- Diffuse and centralized nervous systems are two types of nervous systems in animals.
- Both nervous systems have features of concentration of nerve cells
- Invertebrates can have either a diffuse nervous system or a centralized nervous system.
- The ultimate function of both nervous systems is regulating and coordinating the body of the organism.
What is the Difference Between Diffuse and Centralized Nervous System?
The diffuse nervous system is the most primitive form of the nervous system where nerve cells are distributed usually beneath the outer epidermal layer in an organism, while the centralized nervous system is a complex form of the nervous system where a large number of nerve cells are concentrated in the brain and the spinal cord of an organism. So, this is the key difference between diffuse and centralized nervous system. Furthermore, the diffuse nervous system occurs in animals with radial symmetry, while the centralized nervous system occurs in animals with bilateral symmetry.
The below infographic lists the differences between diffuse and centralized nervous system in tabular form for side by side comparison.
Summary – Diffuse vs Centralized Nervous System
The nervous system is the major regulatory, coordinating, and communicating system in a body. Diffuse and centralized nervous systems are two types of nervous systems found in animals. The diffuse nervous system is a type of nervous system where nerve cells are equally distributed throughout the body, usually beneath the outer epidermal layer, while the centralized nervous system is a complex form of the nervous system where a large number of nerve cells are concentrated in the brain and spinal cord in an organism. Thus, this is the key difference between diffuse and centralized nervous system.
Reference:
1. “Diffuse Nervous Systems.” Encyclopædia Britannica, Encyclopædia Britannica, Inc.
2. “Central Nervous System: Brain and Spinal Cord.” Queensland Brain Institute, 17 July 2018.
Image Courtesy:
1. “Figure 35 01 01” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “1201 Overview of Nervous System” By OpenStax – (CC BY 4.0) via Commons Wikimedia
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