The organism's relationship with the environment and the coordination of the work of the various internal organs are in charge of two important systems: nervous it's the hormonal.
Nervous coordination involves the participation of nerve cells, the so-called neurons.
Hormonal coordination includes the participation of hormones, chemicals that spread through the blood and connect various organs, controlling their actions.
Increased complexity of the nervous system
Nerve coordination of multicellular animals first appears in the cnidaria and is represented by a tissue formed by nerve cells that organize themselves as a network. By touching a hydra with a small needle at a certain point on the body, the generated nerve impulse propagates like a wave. There is no command center of the body.
With the emergence of animals of bilateral symmetry, there are two novelties: a head (cephalization) and nervous system centralization. The head now houses the most developed portion of the nervous system. THE planaryFor example, a flatworm, a central coordinating body begins, in the form of globose masses, the cerebroid ganglia, which act as a "brain". The movements are already more coordinated and the responses more controlled and efficient.
We annelids and arthropodsIn addition to the central ones represented by the “cerebral” ganglia, there are segmental ganglia in the ventral region of the body, constituting a more efficient coordination system of the organism, increasing the responsiveness to environmental stimuli.
We clam, Nervous coordination continues to be done by a ganglionic system, in the most complex, such as octopuses and squids, there are true "brains" controlling the activities of animals, which are capable of performing highly complex actions such as shape recognition. of objects and colors.
We vertebrates The nervous system is much more elaborate and complex. The central nervous tube under considerable improvement from the simplest to the most complex groups, forming specialized organs to control various sensory and motor functions facilitating the adjustment of the organism of this animal to various media.
It was in man, however, that the nervous system reached its peak in complexity, endowing us with a feature nonexistent in the other vertebrates: the capacity for discernment, judgment and logical reasoning, which enables us to think and devise conscious actions in the face of it. environmental stimuli, greatly favoring the domination of the environment, typical of the human species.