The motor neurons are assigned to carry instructions from the interneurons to the muscular system. They trigger the muscle tissues to generate a response, particularly a movement when the body detects stimuli.

The examples of cephalization and specialization in the nervous system of animals are:

1. Nerve nets, nerve cords, and ganglia
a. Nerve nets consist of neurons that show a net-like arrangement.
b. Nerve cords form a ring around the mouth and extend out to the appendages of an animal.
c. Ganglia is the group of interneurons that are linked with each other.

2. Heads
This is exhibited in animals that have cephalization. This is a region where the ganglia, sensory organs, and interneurons are further concentrated.

3. Brains
It is a structure where the cerebral ganglia are further organized. This allows the animal to perform a complex behavior and learning.

An example of an animal with a simple sensory system is a flatworm. It has simple eyespots that act as photoreceptors, which can detect the intensity and direction of light.

On the other hand, cephalopods have well-developed senses. They have complex eyes with an advanced vision that can distinguish colors and shapes, form images, and detect movements. They rely on their sensory system for detecting predators and prey.

When an animal detects a stimulus in the environment, it is prompted to respond to it. In the case of an eagle and the mouse, hunger can be an internal stimulus that triggers the eagle to hunt for food.

When the eagle spotted the mouse on the ground, the sensory neurons deliver the information to the brain using the nerve cells. This causes the brain to react at the sight of food and orders the body to catch the mouse. When the response is carried out by the motor neurons into the body system, the muscles start to move toward the mouse.

From the fishes to mammals, the brain has evolved in terms of its size and complexity.
When compared to other animals, mammals the largest brain with a well-developed cerebrum, which is the thinking region. Having a well-developed brain has caused mammals to perform a complex behavior and learning. In addition, the cerebellum of mammals and birds is more developed than the ones found in fishes, amphibians, and reptiles.