The nervous system is a complex system that controls all vital functions in the body. It consists of the brain, the spinal cord, and the peripheral nervous system. The central nervous system, also known as the CNS, processes stimuli and coordinates responses.
Each nerve cell is specialized to transmit information via nerve fibers. Neurons, synapses, and neurotransmitters play a crucial role in this process. The anatomy of the nervous system shows a clear division into central and peripheral components. In addition, the autonomic nervous system unconsciously regulates processes such as breathing and digestion.
What does the nervous system do?
The nervous system is based on the perception of stimuli and the body’s subsequent action or reaction.
Thanks to the nervous system and the sensory organs, people are able to perceive their surroundings and react accordingly. For example, if a person perceives through their sensory organs—such as their eyes and ears—that a car is about to cross their path, they will quickly move out of the way.
An action that seems so clear and simple at first glance is actually a complex interplay between the nervous system and the muscles.
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The Structure of the Nervous System
The human nervous system is divided into two main parts:
- central nervous system (CNS)
- peripheral nervous system (PNS)
The central nervous system consists of the spinal cord and the brain. The peripheral nervous system comprises all other nerve fibers of the nervous system that run throughout the body. Their function is to supply the brain and spinal cord with information from the body and the environment. Conversely, the peripheral nervous system receives information on how to respond to these stimuli through movements or bodily functions.
Nerve fibers facilitate this exchange of information. The fibers that lead to the central nervous system are called afferent fibers. The fibers that carry information from the central nervous system to the peripheral nervous system are known as efferent fibers.
Another way to classify the nervous system is by distinguishing between
- the somatic nervous system
- autonomic nervous system
The autonomic nervous system controls all important basic functions in the human body and is largely beyond voluntary control. For example, the autonomic nervous system regulates fluid balance, respiration, digestion, and metabolism.
The somatic nervous system, on the other hand, can be controlled largely at will. For example, movements such as raising a hand are consciously controlled via the somatic nervous system. The somatic nervous system serves to transmit sensory information. Touch and external stimuli such as temperature are thus conveyed to the central nervous system.
This short video provides a clear illustration of the human nervous system (in English)
Anatomical Structure of the Nervous System
The nervous system consists of a multitude of nerve cells, their extensions, and glial cells. The human brain is made up of billions of nerve cells.
A defining characteristic of nerve cells is that they are stimulated by changes in the environment and transmit stimuli over very long distances throughout the body. In addition, they can process the transmitted information and relay the signal to other nerve cells or to muscles or gland cells.
Nerve cells (neurons) are therefore cells specialized in the conduction and transmission of electrical impulses. Together with glial cells, nerve cells make up the nervous system. In the peripheral nervous system, ganglia are found in addition to individual nerve cells. A ganglion is a cluster of nerve cells. Since a ganglion is sometimes even anatomically noticeable as a visible thickening, medical professionals also refer to it as a nerve node.
Structure of a Nerve Cell
The following structure is typical of mammalian nerve cells: A nerve cell consists of a cell body and a cell process. The cell process can be either a dendrite or an axon. The dendrite is a branched process primarily responsible for receiving electrical signals from other cells. The axon—also known as a neurite—is a process that serves to transmit electrical signals.
Axons are surrounded by specialized glial cells. Axons transmit a change in membrane potential by causing a change in the cell membrane’s potential through brief ionic currents flowing through specific channels. This process is also called an action potential. The action potential facilitates the transmission of electrical excitation by altering the membrane potential. It is therefore essential for all forms of signal transmission and is considered absolutely necessary for life. The action potential of a nerve cell can even be measured. To do this, researchers have inserted a measuring electrode into the nerve during experiments and determined the cell’s membrane potential using another measuring device.
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Typical Structure of a Neuron
Synapses bridge the gap
The transmission and reception of information in the nervous system do not occur exclusively via electrical excitation. In many cases, synapses are of particular importance for signal transmission in the human body. Synapses facilitate the exchange of information from nerve to nerve.
Nerve cells are generally not directly connected to one another. To exchange information, therefore, a gap must be bridged. Medical professionals also refer to this gap as the synaptic cleft. Synapses consist of the terminal head of an axon, the dendrite, and the gap between them.
Information transmission at synapses rarely occurs electrically; instead, it is usually chemical. The initial electrical signal in the nerve cell is therefore converted into a chemical signal at the end of the axon. Electrical excitation of the nerve cell and its axon triggers the release of chemical messengers—known as neurotransmitters. These are now located in the synaptic cleft and are received by the next nerve cell via specialized binding sites. This chemical information is then converted back into an electrical signal that can continue on its path. This works like a row of dominoes: one cell triggers the next cell to transmit the signal. In this way, a nerve cell can also be directly connected to muscle or gland cells.
Structure of a Synapse
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There are several diseases that are exacerbated by a disruption in synaptic transmission. In depression or Parkinson’s disease, for example, signal transmission through synapses can be disrupted.
Conclusion on the Nervous System
Overall, the human nervous system demonstrates that its structure and function are closely interlinked, and that it controls all bodily functions. The nervous system is divided into the somatic nervous system, which enables conscious control, and the autonomic nervous system—comprising the sympathetic and parasympathetic divisions—which regulates unconscious processes. Complementing these is the enteric nervous system, which independently controls aspects of metabolism and digestion.
The central nervous system, comprising the brain and spinal cord, forms the foundation, with the brainstem and medulla oblongata ensuring vital functions. The nervous system refers to a network of nervous tissue in which neurons transmit electrical signals via axons, enabling the transmission of information. This transmission occurs via afferent and efferent pathways, through which sensory information is received and commands are sent to muscles.
The nervous system and sensory organs work closely together, as stimuli are received and processed as electrical signals. Neurons and glial cells support signal transmission, while the white matter in the central nervous system provides fast connections. The peripheral nervous system connects the central nervous system to peripheral nerves and innervates the entire human body. The nervous system controls complex processes, with the somatic nervous system enabling conscious movements.
At the same time, the autonomic nervous system regulates internal processes, and disorders of the nervous system can significantly disrupt these processes. Overall, it is clear that the nervous system consists of the brain and functions as the overarching control center for the entire body.
FAQ
What is the nervous system?
The nervous system is a central control system in the body. It processes stimuli, controls movements, and regulates the functions of the internal organs.
How is the nervous system structured?
The nervous system consists of the central nervous system—which includes the brain and spinal cord—and the peripheral nervous system. In addition, there is the autonomic nervous system, which controls automatic processes.
What is the function of the central nervous system?
The central nervous system processes sensory information and controls motor responses. It is responsible for thinking, movement, and coordination.
What is the difference between the sympathetic and parasympathetic nervous systems?
The sympathetic nervous system activates the body in stressful situations, while the parasympathetic nervous system promotes rest and recovery. Both are part of the autonomic nervous system.
What are some diseases of the nervous system?
Disorders of the nervous system include, among others, stroke, Parkinson’s disease, and multiple sclerosis. These can impair the function of nerve cells and signal transmission.