Spinal nerves: what they are, types and functions in the body

The spinal cord is a long, fragile tubular structure that begins at the end of the brainstem and continues until it almost reaches the last segment of the spine. Its main function is to transmit signals and commands created in the brain to the trunk, neck and 4 limbs (efferent function) and in turn collect all the sensations and perceptions recorded throughout the body and send them to the brain (function related).

Understanding life without a spinal cord is truly complex, and the proof is in patients with injuries in a part of this fragile but essential structure. Depending on where the trauma occurs, the legs all over the body may experience a total (complete) or partial (incomplete) loss of sensitivity and motor ability below the neurological level of the injury.

Without a doubt, we could define the spinal cord as the center of transmission of all information in the body. It is a neurological highway, the task is to send and receive signals to every part of our body with a specific physiological goal. To accomplish this task, the spinal cord is not alone: has 31 pairs of spinal nerves whose function is to innervate the entire body plane (minus the head). Here we give you the most relevant information about them.

    What are the spinal nerves?

    As we have indicated in the previous lines, the spinal nerves or the spinal nerves are those that extend from the spinal cord and pass through the vertebral muscles to be distributed to all areas of the body.

    The skeletal muscles of our body are innervated by motor and sensory nerves, the function of which is to collect and transmit information to the central nervous system (CNS), from which an effector response is generated. This muscle group consists of over 600 muscles that can be moved at will and together they make up the muscular system. The soft, cardiac musculature is left out of this motor conglomerate, because the movements they perform are not conscious and occur “automatically”.

    Therefore, the spinal nerves are directly related to this muscle part, so that the movements and development of the human being is possible in a three-dimensional environment. It is worth noting that each of these nerves emerges through the spaces of the vertebrae as 2 short branches, called spinal nerve roots. We quickly tell you its peculiarities.

    1. Motor nerve root

    This root, located in the anterior part of the spinal cord, is responsible for transmitting impulses from the spinal cord to the skeletal muscles to promote contraction and, therefore, the production of movement.

    Radiculopathies (injuries or lesions of one or more nerves and their roots) usually cause a characteristic weakening of the muscles innervated by the affected motor root. These become weak, atrophic, flabby and with fasciculations.

    2. Sensitive nerve root

    On the other hand, the sensory root enters from the back of the spinal cord. The nerve fibers that compose it carry sensory information, which will ultimately be interpreted by the brain. Examples of this information are body position, degree of light, touch, ambient temperature, and pain during injury, among many other exogenous and endogenous parameters.

    Consequently, affections of the sensory nerve roots cause a lack of sensitivity in the areas innervated by the injured nerves. Due to this “double” composition of the spinal nerves, it is claimed that these fulfill a function of a mixed nature: they send and collect information equally.

      The 31 pairs of spinal nerves

      Yes, you read that right. 31 pairs of spinal nerves emerge from the spinal cord and innervate virtually our entire body, except for the head and some sections of the neck. Cephalic work is relegated to the cranial nerves, which are 12 pairs of nerves whose function is to connect the brain to the eyes, ears, nose, throat, and various parts of the head and neck.

      Below we present the functionality of all block spinal nerves, as these are divided according to the structures they innervate. Let’s do this.

      1. Cervical nerves (C1-C8)

      These are the nerves of the first 7 cervical vertebrae. They originate from the spinal cord, emerge through the junction holes of the spine and are distributed by sensitive terrains and specific motors..

      The cervical nerves innervate the sternohyoid, sternothyroid, and homohyoid muscles. In general, these muscle groups can be defined as fleshy ribbons that extend from the breastbone / scapula to parts of the neck. Oddly enough, it should be noted that the first cervical nerves do not have roots after 50% of people.

      2. Thoracic nerves (T1-T12)

      This is a total of 12 spinal nerves that emerge from the thoracic vertebrae. Almost all of them are located between the ribs (intercostals), with the twelfth being located under the last rib (subcostal nerve). In turn, the intercostal nerve endings are distributed along the walls of the chest and abdomen.

      These thoracic nerves are involved in the functions of the organs and glands of the head, neck, thorax and abdomen. They are responsible for the innervation of the mammary glands, chest wall, abdominal wall and pelvis. Due to their importance at the nervous level, these spinal nerves are the therapeutic targets of choice for many treatments aimed at managing chronic pain in patients.

      3. Lumbar nerves (L1-L5)

      These are 5 spinal nerves that come from the lumbar vertebrae. They are divided into 2 compartmentalized sections, anterior and posterior. These nerve elements emerge from the spine through the junction holes. However, these nerves should not be conceived as a series of isolated entities: the first 3 and most of the chamber are linked together in this situation by anastomotic loops, forming the lumbar plexus.

      Thus, the lumbar plexus is established between the anterior branches of the spinal nerves L1 and L4. In contrast, the smaller part of the nerve chamber joins with the fifth to form the lumbosacral trunk, which participates in the formation of the sacral plexus.

      4. Sacral nerve (S1-S5)

      These are the 5 spinal nerves that emerge from the sacrum (bone under the L5 lumbar vertebra and above the coccyx) and make up the lowest segment of the spinal cord.. Although the vertebral components of the sacrum are fused to form a single bony entity, each of these nerves is named after the vertebra with which they would be associated.

      These nerves divide into branches, but many of them eventually join together, along with the lumbar and coccygeal plexuses. As we said earlier, this series of interconnections forms plexuses, especially the sacrum and the lumbosacral. The branches of these plexuses innervate the hip, thigh, leg and foot.

      5. Coccygeal nerves

      The coccygeal nerve is the last of the spinal nerves, that is, the number 31. It arises in the medullary cone, Helps form the coccygeal plexus and innervates the sacrococcygeal joint and part of the levator ani.

      8 cervical nerves + 12 thoracic nerves + 5 lumbar nerves + 5 sacral nerves +1 coccygeal nerve: 31 spinal nerves.

      summary

      In this space, we went through the general peculiarities of the 31 spinal nerves that run through our entire body except for the head and parts of the neck. Its function is to emit information from the brain and allow muscle contraction (motor work) and, in turn, to receive all the essential information provided by the extremities and innervated areas (sensitive work).

      Thanks to these pairs of spinal and cephalic nerves, humans are able to develop in a three-dimensional environment, being aware of our own inner state and of what surrounds us in the environment. After reading these lines, a clear concept becomes clear to us: Without our nerve endings, we humans are nothing.

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