Nervous System: what is it, functions, areas and diseases

Have you ever stopped to think about how the Nervous System works? How is your body organized? How does it really work? What structures make up the Nervous System?  We are full of tracks that come and go loaded with data, electrical currents, chemicals, etc. at different rates and for different purposes. In this article, you will find basic elements on how the human nervous system works.

Each element of the Nervous System has its function, its rhythm, and its objective. From now on, I encourage you to sit, relax and enjoy reading. I imagine you’ll be sitting in front of a computer, tablet or on your phone. Let’s suppose that your situation is this last one: “You are waiting and you have decided to enter to see what has been published in CogniFit’s blog. The title of this article has caught your attention and you have entered to read it. As you do so, a car has beeped and startled you. You raise your head to look for the source of the noise, after seeing it was a car, you continue with your reading. At the end of the article, you decide to leave an opinion and type it on your phone. Do you know how you’ve done all that? what parts of the nervous system have intervened in all these cognitive processes? When we finish the article you will have answered these questions.

What is the Nervous System?

We could define the Nervous System as a set of organs and structures, formed by ectodermal tissue whose basic unit are neurons. Ectodermal tissue refers to the outer part that first forms in an embryo (person/animal). Ectoderm would be nails, hair, feathers, etc.

The main function of the Nervous System would be to capture and process quickly all kinds of signs (from the environment or our own body), controlling and coordinating the other organs of the body. In this way, through the Nervous System, we achieve an effective, correct and timely interaction with the environment.

Functions of the Nervous System

For the information to reach our Nervous System, we need receivers, such as eyes, ears, skin, etc. These are the ones that gather the information we perceive from our environment and send the data as electrical impulses through our organism to our Nervous System.

However, we don’t only react to what is in our environment, our heart beats, our liver secretes bile, our stomach takes care of digestion, etc. All these internal processes are also the responsibility of our Nervous System.

What else is it in charge of?

• It controls our hunger and thirst needs, our sleep cycles and regulates body temperature (through the hypothalamus).
• Our emotions (through the limbic system) and thoughts.
• Learning and memory (through the hippocampus).
• Movement, balance, and coordination (through the cerebellum).
• Interpret the information received through all the senses.
• Functioning of our internal organs: our pulse, digestion, etc.
• Emotional physical reactions.

And many more processes.

Characteristics of our Central Nervous System (CNS)

• Its main components are safely protected from the outer environment. Thus the brain, for example, is covered by three membranes, which we call meninges. These, in turn, are surrounded by a bone structure that we call the skull. On the other hand, the spinal cord is also protected by a bony structure, the spine. Look closely at your body, all of our essential organs are protected from the outside.

Think of it as a castle, where the Brain is the King, sitting on his throne and protected by the great walls of his fortress.

• The cells in the CNS are organized in such a way that they create two distinct structures, the white matter, and the gray matter.
• In order to perform its main function (receive information and send signals and orders), a medium is needed. Both the brain and the marrow have cavities filled with cerebrospinal fluid. This, in addition to being the means of transmission of substances, is responsible for eliminating waste and maintaining a homeostasis.

Nervous System Development

During the making of the nervous system in the embryonic stage of development, the SN can be divided into the following parts: Brain and Spinal cord. We explain each one:

Brain

The embryonic brain regions can be considered our primitive brains. They are:

• Forebrain: Through the telencephalon and diencephalon, it’s involved in memory, thought, movement coordination, language development. In addition, it regulates appetite, thirst, sleep and sexual impulses.
• Midbrain: It joins the brainstem and the cerebellum with the Diencephalon. It is responsible for conducting motor impulses from the cerebral cortex to the brainstem as well as sensory impulses from the spinal cord to the thalamus. It deals with aspects of sight, hearing and sleep.
• Hindbrain: Through the cerebellum, the pons and the medulla oblongata, the hindbrain is responsible for processes that are essential for life. These are breathing, blood circulation, swallowing, muscle tone, eye movement, etc. 

Spinal Cord

Through this nervous cord, nerve impulses and information are transmitted, from the brain to the muscles. It has a length of 45 cm and a diameter of about 1 cm, white and flexible. 

We find nerves like:

• Cervical: Cervical area.
• Thoracic: Middle area of the spine.
• Lumbar: Lumbar zone.
• Sacral: Just before the end of the spine.
• Coccygeal: Last pair of vertebrae.

Nervous System Classification

Our nervous system is divided in two, the Central Nervous System (CNS) and the Peripheral Nervous System (PNS).  They both have different functions. PNS is the messenger, it sends signs and information from both the outside and inside of our body to the CNS through our nerves. For the organism to function properly, both systems need to be constantly communicating.

The Peripheral Nervous System is divided into the Somatic Nervous System and the Autonomic Nervous System.

Central Nervous System

Sometimes there are parts of the SN that are injured, producing deficits or problems in functioning. There are specific diseases depending on the brain area that is harmed.

When what is affected is the ability to receive information and process it, to respond to bodily functions, we speak of CNS disorders. We find the following:

Diseases

Multiple sclerosis. A disease that acts on the myelin, damaging the nerve fibers. This causes the impulses to decrease their speed, even stopping. As a consequence, we find muscle spasms, balance difficulty, speech and vision problems.

Meningitis. It is an infection caused by bacteria from the meninges (the membranes that line the brain and spinal cord). It can be triggered by a virus or bacteria. Symptoms include high fever, severe headaches, stiff neck, drowsiness, loss of consciousness and in worst cases, even convulsions. Bacterial meningitis can be treated with antibiotics; however, viral meningitis can’t.

Parkinson’s disease. This chronic disorder is caused by deaths of the neurons in the midbrain (which transmits and coordinates muscle movement). It has no cure and progresses over time. The person with this disease experiences tremors and slowness in voluntary movements.

Alzheimer’s disease. This disease causes problems with the memory, personality, and thought process. Among some of its symptoms, we find confusion, spatial disorientation, dependence on others for daily life activities.

Encephalitis. It is an inflammation of the brain due to bacteria or viruses. Symptoms include headaches, difficulty speaking, loss of energy and body stiffness, fever, convulsions could be triggered and even death.

Huntington:  This disease is neurological, degenerative and hereditary. The brain cells affected are all throughout the brain. The deterioration is progressive and motor problems are part of the symptoms.

Tourette Syndrome: In the “National Institute of Neurological Disorders and Stroke” web page we can find a lot of information about this syndrome. The definition it provides is:

“A neurological disorder characterized by repetitive, stereotyped and involuntary movements and the emission of vocal sounds called tics.”

Peripheral Nervous System and subtypes

As discussed earlier, the SNP is responsible for sending information through the spinal and spinal nerves. These nerves are outside the CNS, but serve to connect both systems. As in the CNS, there are diseases of each subtype, depending on the affected area.

Somatic Nervous System

It is responsible for linking the organism to the external environment. It receives, on one hand, electric impulses with orders to execute voluntary movements of the skeletal muscles. On the other hand, it transmits sensitive information from the rest of the body to the Central Nervous System. We can find diseases like:

• Radial Neuropathy: The damage happens in the radial nerve, which controls the muscles involved in arm extension. This paralysis prevents the extension of the arm.
• Carpal Tunnel Syndrome: Pressure on the median nerve causes carpal tunnel syndrome. This pressure can come from swelling or anything that makes the carpal tunnel smaller. This affects the mobility and sensitivity of some parts of the hand. The most common symptoms are wrist and forearm pain, cramps, and numbness.
• Guillain-Barre Syndrome: On Medical Center of the University of Maryland website it is defined as “A serious disorder that happens when the body’s defense system (immune system) attacks part of the nervous system by mistake. This leads to nerve inflammation causing muscle weakness and other symptoms. “
• Neuralgia: This is a pain disorder caused by a nerve failure in the nervous system, responsible for sending sensitive signals to the Brain. The symptom is a very high acute pain, greater sensitivity in the skin corresponding to the affected nerve.

Autonomic Nervous System

The ANS is responsible for internal organic relationships. It is independent of the cerebral cortex. It receives information from the viscera, regulating its movement. It is also in charge of the physical manifestation of emotions. In turn, it is divided into sympathetic and parasympathetic systems which work together in antagonistic ways. Affecting these systems, we can find diseases such as:

• Hypotension: Blood pressure is poor and insufficient so blood supply doesn’t reach all the organs of our body. You have symptoms like:
  • Dizziness.
  • Drowsiness and momentary bewilderment.
  • Weakness.
  • Confusion and even loss of knowledge.
  • Fainting or fainting.
• Hypertension: The Heart Foundation, defined it as “elevation of blood pressure levels continuously or sustained.”

Hypertension means increased resistance to the heart, which responds by increasing its muscle mass (left ventricular hypertrophy) to cope with this overexertion. This increase in muscle mass ends up being detrimental because it is not accompanied by an equivalent increase in blood flow.

• Hirschsprung: This is a congenital (birth) disorder of the autonomic nervous system, which affects intestinal motility. It is characterized by intestinal obstruction due to the lack of neuronal cells in last part of the large intestine. What happens is that when the waste accumulates, there is no signal to report to the brain, therefore, producing an accumulation. This leads to abdominal bloating and severe constipation. The treatment is surgical.

Like we explained, within the Autonomous SN we can distinguish between:

• Sympathetic Nervous System: It functions when activation is required. Its function is to discharge energy, to satisfy vital objectives. For example, it contracts the pupil, inhibits salivation, accelerates the pulse, relaxes the bladder.
• Parasympathetic Nervous System: It functions when relaxation is required, mainly it intervenes in the recovery processes. For example, it dilates the pupil, stimulates salivation, decreases the pulse, contracts the bladder.
  

The examples in this last section might seem a bit odd, does the contraction of the bladder go together with relaxation? saliva inhibition is related to activation?The explanation is that activation does not refer to conducts that require energy, rather when a situation activates us, these consequences take place. For example, if they rob us on the street.

• Your pulse accelerates, your mouth is dry and even if you are very afraid, you could even pee yourself.
• When the fear of robbery has passed and you are left unharmed, you relax. Your parasympathetic system starts acting and your pupils return to their natural state, your pulse is reduced and our bladder returns to its normal contraction.

Nervous System Conclusions

As you might have noticed our organism is intricate and full of different structures, parts, organs, types, subtypes, etc.  This could not be otherwise, we have evolved to become more complex mammals.

This article is a mere outline of how our brain and nervous system works. We can continue adding more information and structures, however, we wanted the article to be as clear as possible.  What we intended is that you can know what the Nervous System is, how it is composed and the functions performed by each part.

Returning to the scenario at the beginning of the article: “You are waiting and you have decided to enter to see what has been published in CogniFit’s blog. The title of this article has caught your attention and you have entered to read it. As you do so, a car has beeped and startled you. You raise your head to look for the source of the noise, after seeing it was a car, you continue with your reading. At the end of the article, you decide to leave an opinion and type it on your phone.”

We will gradually discuss the different parts of the Nervous System that take part:

• Being seated and keeping a posture: The central nervous system acts through the hindbrain in order to maintain tone, blood circulation, etc.
• Feeling your phone on your hand: The Somatic Peripheral Nervous System perceives through touch and sends information to the CNS.
• Processing the information we are reading: CNS, through the Brain, receives and processes the information we read.
• Raise your head and move your eyes towards the car that has beeped: Sympathetic Nervous System is activated. 
• We continue reading the post: Parasympathetic relaxes the organism. 

Now it’s your turn! What did you think of this guide? Have you solved your doubts about the Nervous System? If you want to add information, ask, clarify concepts … as always, you can comment below the article!

This article is originally in Spanish written by Patricia Sanchez Seisdedos, translated by Alejandra Salazar.

Alejandra Salazar

Alejandra is a clinical and health psychologist. She is a child specialist with a diploma in evaluation and intervention in autism. She has worked in different schools with young children and private practice for over 6 years. She is interested in early childhood intervention, emotional intelligence, and attachment styles. As a brain and human behavior enthusiast, she is more than happy to answer your questions and share her experience.