What is the Difference Between Diffuse and Centralized Nervous System

The main difference between diffuse and centralized nervous system is that the diffuse nervous system consists of a nerve net equally distributed throughout the body whereas the centralized nervous system consists of nerve cells concentrated in the brain and spinal cord. 

Diffuse and centralized nervous system are two types of nervous systems in animals. They are classified based on their organization. The diffuse nervous system is the most primitive form of nervous system in animals while centralized nervous system is the well-developed form of the nervous system.

Key Areas Covered

1. What is the Diffuse Nervous System
     – Definition, Organization, Occurrence
2. What is the Centralized Nervous System
     – Definition, Organization, Occurrence
3. What are the Similarities Between Diffuse and Centralized Nervous System
     – Outline of Common Features
4. What is the Difference Between Diffuse and Centralized Nervous System
     – Comparison of Key Differences

Key Terms

Central Nervous System, Centralized Nervous System, Cephalization, Diffuse Nervous System, Nerve Net

What is the Diffuse Nervous System

The diffuse nervous system or the nerve net is the most primitive form of the nervous system that occurs in animals. The most significant feature of this type of nervous system is the presence of nerve cells equally-distributed throughout the body of the organism, generally beneath the outer epidermal epithelial layer. However, this nervous system may contain small local concentrations of nerve cells called ganglia throughout the body.

Figure 1: Development of the Nervous System

Furthermore, diffuse nervous system occurs in animals with bilateral symmetry, including echinoderms like sea stars, sea urchins, sand dollars, sea cucumbers, and sea lilies, ctenophores or comb jellies, and cnidarians like hydroids, jellyfish, sea anemones, corals.

What is the Centralized Nervous System

The centralized nervous system is the more-developed form of the nervous system, which occurs in animals with bilateral symmetry. It occurs in vertebrates, cephalopods, mollusks, arthropods, annelids, and flatworms.

Figure 2: Organization of Human Nervous System

The main significant feature of the centralized nervous system is the concentration of nerve cells in the central part of the body. It allows the formation of the central nervous system in vertebrates with the brain and the spinal cord. Cephalization is another significant feature of invertebrates with a centralized nervous system. It refers to the concentration of the nervous control and sense organs at the anterior end of the body, forming the head or the brain.

Similarities Between Diffuse and Centralized Nervous System

• Diffuse and centralized nervous system are two types of nervous systems that occur in animals.
• They are classified based on the distribution of nerve cells in the nervous system.
• Also, the main function of both types of nervous systems is to coordinate between the internal or external stimuli and responses of the body.
• Furthermore, the structural and functional unit of both types of nervous systems is nerve cells or neurons.

Difference Between Diffuse and Centralized Nervous System

Definition

The diffuse nervous system refers to the most primitive nervous system that has its nerve cells distributed throughout the organism, usually beneath the outer epidermal layer. Whereas, the centralized nervous system refers to a type of nervous system in vertebrates, consisting of the brain and the spinal cord, which coordinate the activity of the entire nervous system. Thus, this is the main difference between diffuse and centralized nervous system.

Distribution of Nerve Cells

Distribution of nerve cells is another difference between diffuse and centralized nervous system. The diffuse nervous system has its nerve cells distributed throughout the organism while the centralized nervous system has its nerve cells concentrated into the central nervous system.

Organization

Furthermore, the diffuse nervous system is the most primitive form of the nervous system while the centralized nervous system is the most developed form of the nervous system.

Type of Animals

Another difference between diffuse and centralized nervous system is that the diffuse nervous system occurs in Echinodermata, Ctenophora, and Cnidaria while the centralized nervous system occurs in Vertebrata, Cephalopoda, Mollusca, Arthropoda, Annelida, and Platyhelminthes.

Body Symmetry

Moreover, the diffuse nervous system mainly occurs in the animals with radial symmetry while the centralized nervous system occurs in animals with bilateral symmetry.

Conclusion

The diffuse nervous system is the most primitive form of the nervous system, which occurs in animals with radial symmetry. It contains a nerve net equally distributed throughout the body. On the other hand, a centralized nervous system is a more developed form of the nervous system, which occurs in animals with bilateral symmetry. It contains concentrated nerve cells in the central part of the body such as the brain and the spinal cord. Therefore, the main difference between diffuse and centralized nervous system is the organization of nerve cells within the nervous system.

References:

1. Lentz, Thomas L., and Solomon D. Erulkar. “Nervous System.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 21 Dec. 2018, Available Here

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