The neuron.

It is the structural and functional unit of the nervous system. Neurons may have different shapes and sizes. It is estimated that the brain contains about 100 billion neurons.

Neurons have specialized in the reception and integration of signals coming from the domestic environment, the external environment or other neurons.

Note; integration: def.: Give integrity to one thing, compose a whole with its component parts.

Ex. Eye, Ear, capture information: hunger.

Now take the information. The neurons also have specialized integrated to convey information to muscles, glands or other neurons.

What specialize neurons?

* Capturing the information to -> neurons receiving
* Bring the information to -> motor neurons.

What is the function of neurons?

Neurons have the ability to communicate with precision, speed and long distance with other cells, whether nerve, muscle or glandular. Through neurons transmitting electrical signals called nerve impulses. This transfer is much faster than the diffusion processes that usually occur in cells. The nerve impulse, neurons in a living organism, travels from the dendrites (where they receive encouragement), toward the terminal presináptica.

What requires one neuron to respond adequately to a stimulus?

Neurons up and interconnected components of the nervous system: sensitive, inclusive and engine. Thus, a stimulus that is captured in one region sensory surrender certain information that is conducted across the neurons and is analyzed by the component integrator, which can produce an answer, whose signal is conducted through neurons. The answer is enforced by action motor (muscle contraction glandular).

It is the structural and functional unit of the nervous system. Neurons may have different shapes and sizes. It is estimated that the brain contains about 100 billion neurons.

Neurons have specialized in the reception and integration of signals coming from the domestic environment, the external environment or other neurons.

Note; integration: def.: Give integrity to one thing, compose a whole with its component parts.

Ex. Eye, Ear, capture information: hunger.

Now take the information. The neurons also have specialized integrated to convey information to muscles, glands or other neurons.

or cell body. It contains a nucleus or cytoplasm pericarion and organelles that control and maintain the structure and functioning as cell lysosomes, mitochondria, Golgi apparatus, in addition to the Nissl body, which is an orderly array of rough endoplasmic reticulum. There are also the neurofibrillas or filaments that form the cytoskeleton.

It should be remembered that the ribosomes are the site of synthesis of proteins that the neural and rough endoplasmic reticulum (RER) is named for its substance Nissi characteristic blue stain that is obtained with the dye of Nissl.

They are short cytoplasmic extensions. It is part sensory or sensitive, gather information, filiformes (thin parts that make nexus) and highly branched, reaching into the tree dendrítico.

Because the tree is dendrítico portion of the receiving neuron, then the dendrites specialize in receiving nerve impulses and bring into the cell body.

As the dendrites have a low excitability, the momentum is going to spread (r. Spread, disperse, separate things together in different places) in a passive way.

The axon leads manufactured molecules in the cell nucleus to the terminals and leads nerve impulses from the cell body to other neurons, muscles or glands, so thanks to a neuron axon establishes contact with others.

A half neuron receives about 10,000 contacts and some neurons in the cerebellum receive about 150,000 contacts. This gives us an idea of how complex it is the network.

Overall, the various axons traveling together, forming nerves. They can form bundles of hundreds or thousands of axons linked by connective tissue, like a telephone cord, but where each axon is capable of transmitting a signal separately.

Nerves (set of nerve fibers) are born of the CNS and spread throughout all regions of the body. Within the CNS, instead nerves are called Pathways.

The axons that are needed to drive quickly wrapped with layers of white fat or myelin.

Notes: myelin: Definition. It is an insulation layer that forms around the nerves, including those in the brain and spinal cord, and is it consists of protein and fatty substances. The purpose of the myelin sheath is to enable the rapid and efficient transmission of impulses along the nerve cells. When myelin is damaged, impulses are interrupted, which may cause diseases such as multiple sclerosis.

Note: Multiple Sclerosis: It is a disease that impairs areas of myelin along the neurons and produces tremor, loss of coordination and paralysis of body parts. You can attributed to a type of autoimmune disease.

Notes: Autoimmune disease: An autoimmune disease is a disease characterized by action toward the effectors immunological components of one's own body biology. In this case, the immune system becomes the aggressor and attacked parts of the body instead of protecting it. There is an exaggerated immune response against substances and tissues that normally are present in the body. The causes are still unknown and are probably the result of multiple circumstances, (eg genetic predisposition)

The axons covered with myelin, this layer of white fat, is interrupted at certain intervals with the bare areas or lymph nodes called axon of Ranvier. The myelin forms of specialized cells that flatten and roll around the axon.

Classification of neurons:

* According to its role
* According to its structure

According to its role

Neurons can be classified or sensitive afferent neurons in leading the drive to central nervous integrator (spinal cord or brainstem). Neurons association or interneurons are centres integrators and connects the motor and sensory neurons. Transmit signals between very precise areas of the CNS. Neurons connection. They send signals between different regions of the CNS……. Motor neurons or efferent leading the nerve impulse (signals) from the CNS to the bodies afectores (muscle or gland).

These four types of neurons are linked by circuits can be simple. Ex. The reflex arc. They can also be joined by circuits can be more complex. Ex. The interconnections in the human brain.

Note: Arc reflection: it is a journey that perform one or more neurons. It is a response to a stimulus such as pain or strokes.

The reflex arc is a functional unit that occurs in response to specific stimuli collected by sensory neurons. Always means an involuntary response, and therefore automatically, not controlled by consciousness.

According to its structure

Neurons pseudounipolar (false goes together and then split). From soma emerge an extension which are then divided into T-shaped, one arm functions as axon and the other as dendrite. Ex. Neurons of the dorsal root ganglia.

Neurons bipolar. They have two separate extensions, emerging two opposite poles of the neuron. They present an axon and a dendrite, and one other end of soma. EJ. In the retina of the eye.

Neurons multipolar. They present an axon and several dendrites arising from different parts of soma. Such neurons predominates in the nervous system of vertebrates. Ex. In the spinal cord.

The axon terminal is divided into branches, each of which ends in several structures called buttons or synaptic terminals presináptica.

The axons of neurons that are outside the central nervous system are covered by a sheath of myelin that is formed by layers of lipids and proteins produced by cells Schwman. The myelin sheath surrounding the axon except in the nodes of Ranvier, which are spaces between myelin sheaths. The axons of neurons in the central nervous system also have myelin, but is produced by cells called oligodendrocytes (glial cells).

Two types of cells form the nervous system, neurons and glia. Neurons are cells excitable leading impulses that make possible all the functions of the nervous system. Moreover, the information glia not lead themselves, but support in various ways depending on the neurons.