Nervous System: Structure, Function and Types of Neurons

Nervous System

The nervous system is responsible for receiving and analyzing its stimuli, captured by the body's sense organs, and producing responses through effector organs. Information transmission is conducted through specialized cells that make up this system: neurons.

Parts of a Neuron

Neurons have three main parts:

• Cell body: the part of the neuron that contains the nucleus and most of the cytoplasm.
• Dendrites: short, branched extensions that leave the cell body. Through the dendrites, neurons connect with each other and receive information.
• Axon: a long, thin extension that branches at its end. Its function is to transmit information to other neurons, muscles or glands.

Within the nervous system, information is transmitted electrically in the form of impulses or currents. Synapses are the specialized areas where neurons establish communication with each other, using neurotransmitters chemical messengers.

There are also two main functions: the spread of the action potential (nerve signal) along the axon, and its transmission to other neurons, effector cells, or the induction of a response.

Central Nervous System

The central nervous system analyzes incoming information and generates the responses. Its areas where cell bodies accumulate are called gray matter, while areas with bundles of axons form the white matter.

The central nervous system is divided into two major centers:

• Brain: located inside the skull, it comprises the cerebrum, cerebellum and brain stem, protected by the skull.
• Spinal cord: located inside the vertebral column, it is the pathway connecting the brain with the rest of the body.

The central nervous system is covered by three membranes called meninges. Between them circulates the cerebrospinal fluid, whose function is to protect the central nervous system.

The Brain

The brain is divided into two hemispheres. The outer layer, called the cerebral cortex, is gray matter and presents numerous convolutions that increase the surface area of the brain. The inner white part constitutes the association cortex, where information is analyzed and responses take place. This area is related to functions such as memory, learning capacity and decision-making.

Cerebellum

The cerebellum lies below the cerebrum and behind the brain stem. It is responsible for coordinating and controlling body movements and posture.

Brain Stem

The brain stem controls functions such as respiratory rhythm, heartbeat and cough reflexes. Its injury can be serious because it is the continuation of the spinal cord and contains vital centers.

Spinal Cord

The spinal cord is protected inside the vertebral column. It controls simple, involuntary acts, such as withdrawing the hand when we feel pain. These are called reflexes.

Peripheral Nervous System

The peripheral nervous system connects the central nervous system with the sense organs and the organs that carry out responses. It is made up of a neural network that runs through the entire body.

According to its function, nerves are classified into two types:

• Sensory nerves: carry information from the sense organs to the central nervous system.
• Motor nerves: carry orders from the central nervous system to different organs of the body.

Motor nerves are divided into two types:

• Somatic nervous system: controls voluntary movements of the skeletal muscles.
• Autonomic nervous system: controls involuntary movements of smooth muscles, cardiac muscle and blood vessels.

Types of Nerves

Cranial nerves: nerves that emerge from the brain. Spinal nerves: nerves that emerge from the spinal cord.

A set of anatomical structures makes up the nervous system.