The nervous system is a complex network of nerves and cells that carry messages from the brain and spinal cord to various parts of our body, and vice versa.
The nervous system includes the central nervous system and the peripheral nervous system. The central nervous system is made up of the brain and the spinal cord, while the peripheral system is made up of the somatic and autonomic nervous systems.
The brain consists of four main parts:
- the brain stem
- the brain
- the cerebellum
- the diencephalon
It contains nerve cells called neurons, and cells of specific function called glia.
There are two types of matter in the brain: gray matter and white matter. The gray matter receives and saves impulses, and also corresponds with the part of neuronal cell bodies and the neuroglia, while the white matter is responsible for transmitting impulses to and from the gray matter.
The meninges are the three layers or membranes that line the brain and spinal cord. The outer layer is the dura mater, the central layer is the arachnoid and the inner-most layer is the pia mater. The meninges offer the brain and spinal cord protection, acting as a barrier against bacteria and other microorganisms.
The spinal cord extends from the brain along a tube-like structure. It consists of a series of 31 segments, with a pair of spinal nerves in each of them. This area is called the spinal segment. The motor and sensory nerves are located in the spinal cord. The spinal cord is 43 cm long in adult women and 45 cm long in adult men. It weighs approximately 35-40 grams.
El trabajador más pequeño del sistema nervioso es la neurona. Para cada uno del encadenamiento de impulsos hay una neurona, o una antes del cuerpo o del ganglio de célula, que son como un cuerpo que controla central para las neuronas numerosas que salen periféricamente.
The neuron is the smallest functional unit of the nervous system. We find in these cells in each and every zone of the impulse chain. The preganglionic neuron is located in the brain or spinal cord. In the autonomic nervous system, this neuron sends impulses to an autonomic ganglion. The postganglionic neuron then sends impulses to the target organ.
In the somatic nervous system there is only one neuron between the central nervous system and the target organ, while the autonomic nervous system has two neurons.
Another part of the nervous system is the autonomic nervous system. It consists of three branches:
- the sympathetic nervous system
- the parasympathetic nervous system
- the enteric nervous system
In this area of the nervous system, there are the nerves that trigger the internal organs of the body, over which humans have no conscious control, such as the heartbeat, digestion and breathing.
The nerves of the autonomic nervous system weaken the smooth involuntary muscles and make them function and secrete their enzymes.
The enteric nervous system is the third part of the autonomic nervous system. It is a complex network of nerve fibers that trigger the organs within the abdomen, such as the gastrointestinal tract, pancreas, gallbladder, etc. It contains almost 100 million nerves.