CENTRAL NERVOUS SYSTEM: PARTS AND FUNCTIONS (WITH PICTURES) - GEOGRAFÍA - 2025

The central nervous system (CNS) is one made up of the brain, spinal cord, and optic nerves. It is called "central" because it integrates information from the entire body and coordinates its activity. This system has a wide variety of functions; In general, it can be said that it directs cognitive processes, emotions, movement and the perception of stimuli.

The brain and spinal cord are covered by a protective membrane called the meninges, which make the central nervous system the most protected in the body. In the subarachnoid space of the meninges, cerebrospinal fluid circulates, which protects the brain and maintains its metabolism.

Brain and spinal cord

The basic unit of the central nervous system is the neuron. It is a special type of nerve cell that transmits electrical and chemical messages to exert different effects on its neighboring cells.

In addition to neurons, glial cells are also distinguished, known as “support cells”. They serve to support neurons, move them, and give them oxygen and nutrients. There are more of these cells than there are neurons, in a ratio of 10 to 1.

Parts of the central nervous system

In general, the central nervous system is made up of the brain and spinal cord, although the retina, optic nerves, olfactory nerves, and olfactory epithelium are sometimes included. This is because they connect directly with brain tissue.

On the other hand, two parts of the central nervous system are also often spoken of: the white matter and the gray matter.

The white matter is one that is formed by the myelinated axons of neurons and oligodendrocytes.

Myelin, which lines axons and makes nerve impulses travel much faster, turns the area white. The white matter is in the innermost areas of the brain, and in the outermost areas of the spinal cord.

Gray matter, on the other hand, is made up of neuronal somas (cell nuclei) and dendrites without myelin. In the brain it is located in the outermost layer, while in the spinal cord it is located in the interior.

Below, you can learn more about the main components of the central nervous system:

Brain

The brain is the most complex organ in the body. It is made up of about 100 billion neurons, which make innumerable connections between them. This organ uses 20% of the oxygen we breathe, constituting 2% of our complete weight.

The brain is usually divided into lobes: the occipital, parietal, temporal, and frontal lobes. Scientists have discovered through years of research that each of them is linked to a group of functions.

However, do not forget that this is very general. Our behaviors depend more on circuits distributed throughout the brain and groups of neurons than on a localized portion of the brain. The brain lobes are:

- Occipital lobe: located in the back of the brain, they receive visual information and interpret it.

- Parietal lobe: they are in front of the occipital lobes. They are associated with the processing of sensory information (touch, temperature, pain, taste…) and spatial perception.

- Temporal lobe: they are located on each side of the brain, behind the ears. They are important for processing auditory information, language and memory.

- Frontal lobe: it is in the front part of the brain. It participates in voluntary movements and coordinates with other parts of the brain for speech, organization and planning, memory, etc.

In the functions section you can learn more about the tasks that each lobe performs.

On the other hand, cortical and subcortical structures also tend to differentiate in the brain. The former are the outermost and evolutionarily new layers. While the latter are the closest to the base of the skull, interior and primitive.

The cerebral cortex has more complex and elaborate functions typical of primates and humans, while the subcortical structures handle simpler tasks shared by mammals (limbic system), and even reptiles (brain stem).

Spinal cord

Spinal cord in purple / lilac

It is a continuous structure that runs from the brain, starting at the base of the skull, to the end of the spine.

It connects to a part of the brain called the brainstem, staying in the spinal canal. Different nerve roots emerge from the medulla on both sides of the body. Thus, it connects with the peripheral nervous system that reaches the joints, muscles and skin.

Brainstem

The spinal cord carries messages back and forth between the brain and peripheral nerves. For example, the brain can give motor commands that travel up the spine and reach the muscles. Or, information from the senses can travel from sensory tissues (such as the skin) to the spinal cord. From there, it will reach the brain.

It also allows us to give rapid motor responses, such as reflexes, without the information having to be processed in the brain. For example, when we quickly remove our hand from a very hot object.

Cranial nerves

The 12 pairs of cranial nerves

There are 12 pairs of cranial nerves that exit directly from the brain, passing through holes in the skull. They are used to exchange information between the brain and other parts of the body, especially the head and neck.

Of these 12 pairs, the optic, olfactory, and terminal pairs are considered part of the central nervous system. The optic nerves are located behind the eyes, and carry visual information from the retina to the brain.

The olfactory nerves carry scent messages to the upper part of the nasal cavity, which is called the olfactory bulb. This transmits the information to the brain.

While the role of the terminal cranial nerves is not exactly known. Some believe that it is a holdover or involved in the production of pheromones.

Central nervous system functions

It is enormously complex to list all the functions of the central nervous system. It has so many functions and so varied that it is more appropriate to focus on studying each region separately.

- Brain functions

The brain plays a central role in regulating most bodily functions, coordinating a wide variety of tasks.

It ranges from the secretion of hormones, the level of consciousness, the simplest movements, the perception of stimuli, emotions, the creation of memories, to language and thoughts.

To perform these functions, the brain has certain areas dedicated to them. However, most higher functions such as problem solving, language, reasoning or planning require different areas of the brain to work together.

We can divide the brain functions according to each lobe:

Occipital lobe

It contains the visual cortex, the area that controls visual perception. Projects information to other parts of the brain for identification and interpretation.

Parietal lobe

It integrates information that comes from the senses, such as touch or taste. In addition, it regulates the perception of the position of the own parts of the body, and the relation of oneself with respect to the space.

That is, it is important for spatial perception and navigation. It has also been found to be related to number recognition and performing mathematical calculations.

Temporal lobe

It processes some aspects of language in addition to auditory information. Store long-term memories with the help of the hippocampus. Also, it is important in complex visual processing such as face recognition.

It also contains the amygdala, a fundamental structure for memorizing and triggering emotions (especially negative).

Frontal lobe

It is associated with complex and elaborate functions. Among them are attention, working memory, motivation, planning, self-control, expression of language and emotional regulation.

On the other hand, there are fundamental structures of the brain that are not linked to a specific lobe. Some examples are:

Basal ganglia

The basal ganglia are located inside the brain and control voluntary movements. They are also linked to learning motor sequences such as learning to play an instrument or rollerblading.

Cerebellum

Cerebellum (light blue)

It is a structure located at the base of the brain. It is traditionally associated with balance and coordination.

In addition, it participates in fine and precise motor control, and the generation of muscle tone. However, it has been found to be involved in some types of memory, attention, spatial skills, and language.

Thalamus

It is located in the center of the brain. It receives motor and sensory information and transmits it to other parts of the cerebral cortex. It is associated with awareness, alertness, and sleep.

Hypothalamus

Hypothalamus in orange

It is just above the brain stem and is responsible for releasing neurohormones, which serve to regulate body temperature, hunger, and thirst.

Medulla oblongata

It is located under the skull, and triggers many involuntary functions such as breathing, maintaining blood pressure, sneezing, or vomiting.

- Functions of the spinal cord

The spinal cord is the intermediary between the brain and the peripheral nervous system. It is very important in the sensory perception of the joints, muscles and skin; in addition to controlling movement.

The spinal cord can direct movements without the participation of the brain, such as reflexes or while walking.

This structure can coordinate all the muscles necessary for walking, with only the brain intervening to initiate or interrupt the process. Just as it would intervene if unforeseen events appear, such as an object that prevents progress.

Central nervous system diseases

Because this system is so vast and complex, a large number of different conditions can alter its operation.

Injuries or illnesses that affect this system can cause the loss or deterioration of some of the functions mentioned. This can lead to a lesser or greater degree of disability. Depending on where the damage occurs, symptoms can vary greatly.

The main factors that can impair the functioning of the central nervous system are:

Trauma

This is any type of acquired damage (from an intense blow, for example) to the brain or spinal cord. Depending on the area injured, symptoms can range from paralysis or motor problems to apathy or disinhibition.

Strokes

It consists of the interruption of blood flow to the brain. As neurons run out of oxygen, they die.

Therefore, the results are similar to those arising from trauma. However, strokes can affect more specific circuits in the brain. For example, those in charge of producing or understanding language. A stroke in these circuits can cause aphasia.

Infections

Some microorganisms or viruses have the ability to invade the central nervous system, as occurs in meningitis or encephalitis. Viruses that can affect the central nervous system are herpes virus, herpes zoster, enteroviruses, arboviruses, etc.

Degeneration

There are conditions in which for reasons not yet defined, the brain or spinal cord progressively degenerates. This is what happens in dementia. Some examples are Alzheimer's, Parkinson's, amyotrophic lateral sclerosis, Huntington's chorea, etc.

Structural neurodevelopmental disorders

These are birth defects in which some part of the central nervous system has not developed or matured properly. This is seen in anencephaly, for example, in which the baby is born without some parts of the skull, scalp, and brain.

Intellectual disability, ADHD, learning disorders (such as dyslexia), autism or language disorder are also categorized as neurodevelopmental disorders.

Tumors

Benign or cancerous tumors can affect any part of the central nervous system and cause symptoms that depend on where they appear. A cyst or tumor presses on the tissues around it, causing them to compress and increasing intracranial pressure.

Autoimmune diseases

Sometimes the immune system can mistakenly attack healthy tissues in the brain or spinal cord, mainly myelin in some areas. This is what happens in acute disseminated encephalomyelitis and in multiple sclerosis.

Additionally, there are many diseases of the central nervous system that arise from a combination of the listed factors and gene involvement. For example, this occurs with psychiatric and psychological disorders such as depression, bipolar disorder, or schizophrenia.

References

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