Unveiling the Complexity: Understanding the Nervous System

Unveiling the Complexity: Understanding the Nervous System

An essential part of what we call the “human mind” is the nervous system. It includes the brain and spinal cord as well as the peripheral nervous system, which includes all nerves that emanate from the central nervous system – CNS for short. 

The many billions of nerve cells are the prerequisite for us to be able to think, act, feel and communicate with one another. Every nerve cell has many side arms that pass on impulses to other cells. Like an up-to-date news service, they use signals to tell the brain everything that’s happening in the body and what we call the “outside world.” The impulses transmit pain, hunger, sounds, smell or heat.

The brain contains thousands of nerve cells that filter and analyze signals from the sensory organs and other endogenous receptors and convert them into response signals for the peripheral nervous system. The central nervous system receives oxygen and nutrients via a sizeable vascular network. The skull and spine, three layers of connective tissue and the cerebrospinal fluid, which serves as a buffer, protect it from damage.

Autonomous System

The autonomic (involuntary) system, also known as the vegetative nervous system, influences the activities of the heart, lungs, stomach, intestines, bladder and blood vessels. All the information from different organs converges in the hypothalamus, which controls this system. He regulates this information with the help of the autonomic and endocrine systems. When more oxygen is consumed during vigorous physical activity, the hypothalamus receives the information “oxygen starvation” and causes the respiratory and heart rates to increase. When staying in oxygen-poor regions – for example, in the mountains – the body adapts accordingly to increase the production of red blood cells by up to forty per cent so that more oxygen can reach the body tissue.

The autonomic nervous system has the task of regulating the behaviour of the human body in such a way that activity and relaxation remain in balance. This is achieved through the antagonistic interaction of the parasympathetic and sympathetic nervous systems. The sympathetic system increases performance in moments of stress and danger, while the parasympathetic system is responsible for relaxing and regenerating the body.


The most important organ of the central nervous system is the brain, and a control body made up of over ten billion nerve cells, each of which, in turn, is connected to up to 10,000 other nerve cells. The brain’s structure resembles a walnut, and its consistency resembles a pudding. 


In a newborn, it weighs about 330 grams. It weighs an average of 1.3 kilograms in an adult, with the cerebrum taking up the central part. A connection between the size of the brain and human intelligence is now considered impossible. (By the way, the Neanderthals had larger brains than we do!) Different regions of the brain each have specific functions.

The brain is responsible for all of our activities, both conscious and unconscious. It can be described as the “seat of one’s personality” – with all one’s feelings, thoughts and abilities. The brain is connected to the body muscles via two thick nerve cords – the so-called pyramidal tract – and can give them instructions on how to behave.

Three membranes protectively surround the brain: the dura mater, the cobweb and the inner meninges. Inflamed meninges are the cause of meningitis.

A distinction is made between the brain regions of the cerebellum, brainstem, cerebrum, cerebral cortex, diencephalon, thalamus and hypothalamus.


The cerebrum is responsible for our thinking and perception; here, one suspects the origin of intelligence and judgment of man. A longitudinal furrow divides it into two mirror-similar hemispheres, capable of performing different functions simultaneously. In the centre of the hemispheres are the basal ganglia – those “grey cells” that Agatha Christie’s famous detective Hercule Poirot so often and erroneously blamed for his brilliant ideas. Instead, they control the involuntary movement patterns of our skeletal muscles, such as when sitting or walking.

Some people’s talents make it easy to see which side of their brain (hemisphere) is more active, such as whether they’re more mathematically gifted or musically inclined. A connection is also suspected between the development of the cerebral hemispheres and left-handed and right-handed people. Putting it simply, removing left-handedness from children could even cause mental problems. Last, the brain’s hemispheres determine which of our two eyes we prefer to see – for example, when photographing something. Some scientists even believe there is a “logical seeing” and an “intuitive seeing” eye, as with the cerebral hemispheres.

cerebral cortex

A grey matter called the cerebral cortex forms the brain’s outer layer of nerve cells. Many furrows and curves greatly enlarge the surface of the cerebral hemispheres. Four so-called lobes are distinguished as parts of it.

The temporal lobe is responsible for smell, hearing and speech; the parietal lobe for touch and taste; the occipital lobe for sight; and the frontal lobe – believed to be the seat of consciousness – for movement, speech and thought processes. However, this rough classification is to be considered with the reservation that brain research still faces many puzzles on the subject of “consciousness” – and probably always will.


The brainstem connects the brain to the spinal cord. This is where all the information comes together and intersects in the lower part. Because of this crossover, the left side of the brain controls the right side of the body and vice versa.

The brainstem is responsible for general vital functions. Its structures control heart rate, blood pressure, and breathing. The wake-sleep centre is also located here.


The cerebellum, which is only about an eighth the size of the cerebrum, primarily controls our movement processes. 

With the help of sensitive nerves, body movements are constantly controlled, and impulses that lead to muscle contractions are sent. These unconscious processes are a prerequisite for body balance and motor skills. All the information that our sensory organs pass on also reaches the cerebellum.

nerve cell

Millions of interconnected nerve cells – called neurons – make up the nervous system. They are connected to neighbouring cells via many extensions – called axons. The neurons have different functions, according to which they are divided into three main groups:

  • Sensory neurons transmit impulses from the body’s receptors to the central nervous system.
  • Interneurons are intermediate nerve cells that process impulses.
  • Motor neurons cause voluntary and involuntary body movements.

All nerve cells have the same basic structure as the rest of the body’s cells: a cell nucleus. In addition, they contain one or more root-like extensions, the dendrites. These have the task of transmitting impulses to the nerve body.

An axon is a single fibre that transmits impulses as an extension of the nerve cell. Their end touches either the dendrites of the nerve cell or special cell receptors. These connections are called synapses. The nerve impulses are transmitted via particular carrier substances (transmitters) in the synapses.

Certain cells in the central and peripheral nervous systems provide substance transport, insulation, and scarring.

peripheral nervous system

The peripheral nervous system forms the bridge from the central nervous system to all body parts. Each nerve is a sensory and motor nerve fibres, blood vessels and connective tissue bundle.

The primary nerves are 43 pairs of nerves. Twelve of them make up the cranial nerves that leave the skull at the base of the skull. The remaining 31 pairs, spiral nerves, pass through the spinal cord.

The peripheral nervous system works partly involuntarily, partly voluntarily, or, to put it another way, partly autonomously, partly somatically.


About forty centimetres long, the tubular grey spinal cord has the vital function of transmitting signals to the central nervous system. Without this “information cable” about half a centimetre in diameter, we would not be able to control our actions.

The marrow comprises nerve cells that form a cord of tissue. This extends about the finger’s width from the brain’s underside across the spinal canal to the area of ​​the second or third lumbar vertebra.

In the medulla, sensory and motor neurons run from the brain to the peripheral system and vice versa. The spinal cord is a conduit in which the nerve cells are switched and forwarded according to their tasks. It only weighs about 25 grams and is located inside the spine, so the risk of damage is relatively low. Injuries to the spinal cord can lead to sensory disturbances or paralysis.

Even simple reflexes are controlled by the spinal cord. The sensory and motor nerve cells are switched directly with a corresponding stimulus, leading to fast reactions. For example, if someone accidentally touches a hot stove with their hand, the direct switching causes the hand to jerk back at lightning speed.

somatic system

The somatic (voluntary) system has two functions: On the one hand, it receives sensory stimuli and transmits them to the central nervous system for processing. Conversely, however, it also transmits signals from the central nervous system to the skeletal muscles, which cause the body to move according to the information.

central nervous system

The hypothalamus, a small area in the midbrain, connects it to the endocrine system. It is in contact with the pituitary gland (hypophysis) via a portal vein system and regulates its hormone release. Most of the exchange of information takes place via this system through hormones produced in the nerve cells (neurons) of the hypothalamus. In this way, it regulates body temperature, heartbeat, kidney function, hunger and thirst, sleeping rhythm, and sex drive.

The midbrain lies between the cerebellum and the cerebrum. The autonomic nervous system, which is responsible for our body’s energy, heat and water balance, is controlled from here. In addition to the hypothalamus, the diencephalon has three other “switching points”: thalamus (sensory perception), epithalamus (olfactory perception) and subthalamus (motor functions).

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