Innervation

The Innervation binds organs, tissues and body parts to the nervous system and thus enables the complex interaction within the body. Electrical and biochemical stimuli are transmitted via the nerve cells and nerve fibers. Damage to nerve structures can lead to motor disorders, abnormal sensations and even life-threatening consequences.

What is the innervation?

In medicine, innervation is the functional supply network made up of nerve tissue. Organs as well as parts of the body or types of tissue such as muscle tissue are innervated with nerve cells and nerve fibers.

The nerve cells (neurons) are responsible for perceiving stimuli and processing nerve impulses. Nerve fibers are the extensions of nerve cells. They are also known as axons, including the surrounding shell structures, and carry electrical excitation away from the nerve cell body. The innervation by axons, their sheaths and neurons ultimately ensures the functioning of all body processes.

The neurologist understands the somatic innervation to mean the sensory and motor innervation. The vegetative innervation is vital and is divided into sympathetic and parasympathetic innervation.

Function & task

The innervation takes over sensitive, vegetative and motor functions in the body. Sensitive nerve fibers are connected to receptors. These receptors register sensations. An example of this are the mechanoreceptors of the skin's layers that register touch and pressure. The nociceptors perceive pain stimuli and the skin's thermoreceptors are responsible for temperature perception.

The nerve fibers connected to these sensory receptors transmit the excitations in an afferent manner, i.e. to the central nervous system. This transmission usually takes place via projection and ensures that a stimulus reaches the brain and ultimately the thinking consciousness.

Within the group of sensitive innervation, one sometimes speaks of sensory innervation when it comes to the sensory organs of the eye, ear and throat. In contrast, the innervation of the internal organs is also called viscerosensitive innervation. These nerve fibers transmit sensations from the internal organs to the central nervous system.

Usually these neurons and axons are counted as part of the vegetative nervous system, since without this conduction of excitation no life would be possible. The autonomic nervous system consists of parasympathetic, sympathetic and enteric innervation. These nerve connections control digestion, breathing, glandular functions and the movement of the heart muscle.

Unlike the heart muscle, the skeletal muscles are not connected to an autonomous nervous system. They are innervated by motor nerves. This means that excitation is transmitted to your individual muscle fibers via the so-called motor endplate. In this way, a command from the central nervous system stimulates the skeletal muscles to contract.

In this case, stimuli are not transmitted into the central nervous system, but rather from the central nervous system. In connection with the motor nerves of the skeletal muscles, the doctor speaks of an efferent innervation. However, afferent nerve fibers run in every muscle, which register the current tone of the muscles and pass it on to the central nervous system.

The transmission of action potentials within the nervous system takes place either biochemically or bioelectrically. So-called neurotransmitters are used for biochemical transmission. These neurotransmitters are biochemical messenger substances. They are released from one nerve cell and recognized by other nerve cells. In this way, nerve cells that are not directly next to each other can also communicate.

The electrical transmission in the nervous system, on the other hand, takes place with the help of charged salt particles from the cell membranes. The membrane potential of the cells results from the difference between the outer and inner milieu of the cell. This difference is determined by the membrane and is applied as an electrical voltage. In this way, a compensating current is generated, which forms the heart of electrical signal transmission.

Overall, the perception, movement and internal processes of an organism would not be possible without innervation.

Illnesses & ailments

Various processes in the nervous system can cause nerve cells to die. One of the most common causes of this is poor blood flow. For example, if the heart fails, the blood flow is interrupted, which can damage nerve tissue.

Often in this case, the innervation of the brain is affected. This cell death of nerve cells in the brain can trigger different symptoms. Motor functions can be impaired, as can perception.

Metabolic disorders of the nerve tissue can also trigger functional disorders or impulse transmission disorders. With such metabolic disorders, toxins often accumulate in the brain.

Inflammation in the nervous system can cause just as much damage. Such phenomena occur, for example, in multiple sclerosis, in which the immune system incorrectly recognizes the body's own cells as foreign and attacks tissue of the central nervous system.

The most common early symptoms of nervous system damage are changes in taste, movement disorders or abnormal sensations such as numbness and tingling. Abnormal sensations can be present, for example, in the form of diabetic polyneuropathy, in which a lack of blood circulation is responsible for the damage.

Infectious diseases such as borreliosis or degenerative diseases can also be associated with damage to the nervous system. In some circumstances, even mechanical injuries such as traumatic brain injury can affect the nervous system.

In severe cases, nerves are severed in an accident. This can also lead to numbness or motor impairment. Nerve damage in the spine is also particularly dangerous. Severed nerves may sprout out, creating a neuroma that causes significant pain.

Severed nerves can now be put back together under certain circumstances. However, this process is extremely tedious, as nerve fibers only grow one millimeter per day. Therapeutic success is therefore only achieved after a significantly longer period of time than is the case, for example, with the healing of broken bones or wounds.