Question

What is the most primitive type of nervous system?

Answer 1

Diffuse nervous system

1. The diffuse nervous system is considered to be the most primitive nervous system.
2. In a diffuse system, nerve cells are usually distributed throughout the organism, beneath the outer layer of the epidermis.
3. There may be small local concentrations of ganglia or neurons, but high concentrations of neurons, such as the brain, are not found in these systems.
4. Diffusion systems are found in cnidarians (hydroids, jellyfish, sea anemones, corals) and comb jellies.
5. However, the primitive nervous system of these organisms does not preclude long-term, coordinated responses and integrated behavior to the simplest stimuli.
6. An example is the migration of the sea anemone Calliactis to the hermit crab Pagurus shell, depending on the factors present in the outer layer of the empty mollusk shell occupied by the crab.
7. This move requires the highest level of integration.