Nervous system

Nervous system

• It is formed by a combination of anatomically and functionally interconnected structures that provide the regulation, coordination, and integration of the functions of organs and systems of the body, and its interaction with the environment.
• It forms a complex communication system containing at least a trillion interconnected neurons.
• Through numerous receptors the system perceives various stimuli, transforms them into nerve impulses that arrive at nerve centers for processing and forming an appropriate response, which is then directed through effectors to target organs.

It is anatomically divided into the:

• central nervous system (CNS);
• peripheral nervous system (PNS).

According to functional characteristics, it is divided into:

• somatic (animal);
• autonomous (vegetative).

The scheme of the nervous system organization

The morphological substrate of the activity of the nervous system are reflectory arcs.

Reflectory arcs:

• are represented by neural ensembles (chains of neurons) that provide cells and organs responses to signals from the external or internal environment;
• include:
  • afferent element — a sensory neuron that perceives a signal using a receptor and transmits information to various parts of the CNS;
  • associative element — integrative neurons (interneurons), which analyze, integrate the information received and transmit signals to motor neurons;
  • efferent element — motor neuron that transmits signals through the effector nerve ending to working structures;
• signals are carried out only in one direction — from the receptor of a sensory neuron to the effector of a motor neuron, which is due to the presence of synaptic contacts between neurons.

There are simple and complex reflectory arcs. Simple reflectory arcs consist only of sensory and motor neurons. Complex reflectory arcs also include integrative neurons (one or more). Most reflexes are carried out by complex reflectory arcs passing through the nerve centers of both the spinal cord and the brain.

Somatic and autonomous reflectory arcs