Somatic nervous system

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Somatic nervous system
1. (Brain) Precentral gyrus: the origin of nerve signals initiating movement. 2. (Cross section of Spinal cord) Corticospinal tract: Mediator of message from brain to skeletal muscles. 3. Axon: the efferent nerve fiber that carries the command to contract muscles. 4. Neuromuscular junction: muscle cells are stimulated to contract at this intersection
Details
Part of	Peripheral nervous system
Identifiers
FMA	9904
Anatomical terminology [edit on Wikidata]

The somatic nervous system (SNS) is made up of nerves that link the brain and

are responsible for detecting information within and outside of the body.

The somatic nervous system, or voluntary nervous system is the part of the

The movements of our arms, legs, and other body parts are among the functions that the somatic nervous system is in charge of and that we can consciously control. The somatic nervous system consists of nerves carrying afferent nerve fibers, which relay sensation from the body to the central nervous system (CNS), and nerves carrying efferent nerve fibers, which relay motor commands from the CNS to stimulate muscle contraction.^[3]

The a- of afferent and the e- of efferent correspond to the prefixes ad- (to, toward) and ex- (out of).

Structure

There are 43 segments of nerves in the human body.^[4] With each segment, there is a pair of sensory and motor nerves. In the body, 31 segments of nerves are in the spinal cord and 12 are in the brain stem.^[4] Besides these, thousands of association nerves are also present in the body.^{[citation needed]}

Thus the somatic nervous system consists of two parts:

• coccygeal nerves. Peripheral nerves are included in the category of peripheral nervous system.^[6]

• spinal nerves, which have neural fibers originating from the spinal grey matter as their roots.^[7] The cranial nerves VIII (vestibulocochlear), II (optic), and I (olfactory) are regarded as entirely afferent. The exclusively efferent cranial nerves are XI (spinal accessory), XII (hypoglossal), VI (abducens), IV (trochlear), and III (oculomotor). The remaining cranial nerves, X (vagus), IX (glossopharyngeal), VII (facial), and V (trigeminal), have mixed sensory and motor functions.^[8]
  Anatomically, cranial nerves are numbered from I to XII, which indicates their sequential origin from the caudal to the ventral brainstem. Alternatively, they can be postulated in groups based on the developmental functions they perform (sensory, motor, mixed).

Function

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The somatic nervous system's principal goal is to facilitate the organs and striated muscles of the central nervous system so that we can carry out our daily responsibilities.

The

The somatic nervous system controls all

The basic route of

) of muscles, thereby relaying the stimulus to contract muscle fibers.

Reflex arcs

A reflex arc is a neural circuit that creates a more or less automatic link between a sensory input and a specific motor output. Reflex circuits vary in complexity—the simplest spinal reflexes are mediated by a two-element chain, of which in the human body there is only one, also called a monosynaptic reflex (there is only one synapse between the two neurones taking part in the arc: sensory and motor). The singular example of a monosynaptic reflex is the patellar reflex. The next simplest reflex arc is a three-element chain, beginning with sensory neurons, which activate interneurons inside of the spinal cord, which then activate motor neurons. Some reflex responses, such as withdrawing the hand after touching a hot surface, are protective, but others, such as the patellar reflex ("knee jerk") activated by tapping the patellar tendon, contribute to ordinary behavior.

Clinical Significance

A medical condition known as peripheral neuropathy affects the somatic nervous system's peripheral nerve fibers. They can be divided into congenital and acquired disorders based on the causes. They can also be categorized based on whether the

(demyelinating neuropathy) or axons (axonal neuropathy) have the predominant disease. There is a wide range of causes for axonal peripheral neuropathy, most of which are toxic-metabolic in origin and include group B vitamin deficiencies and diabetes. Demyelinating neuropathies do not vary with length. They are frequently immune-mediated, which causes a more widespread involvement of sensorimotor function and an early loss of deep tendon reflexes. When joint position and vibratory sensory loss are present, sensory participation is more selective.

Defects in the central nervous system, peripheral nervous system, or muscle itself are the cause of numerous congenital illnesses of sensory and motor function. Owing to the vast territory encompassed by the somatic nerve system, these ailments may manifest as localized in nature, or as broad and systemic.

Charcot-Marie-Tooth (CMT)

The Charcot-Marie-Tooth (CMT) disease group comprises diverse hereditary illnesses that manifest as chronic, progressive neuropathy that affects both the motor and sensory neurons.[11]

Myasthenia Gravis (MG)

An autoimmune neurological condition called myasthenia gravis (MG) is typified by impaired neuromuscular junction communication.^[12]

Guillain-Barré syndrome (GBS)

A rare but dangerous post-infectious immune-mediated neuropathy is Guillain-Barré syndrome (GBS). It is brought on by an autoimmune reaction that destroys peripheral nervous system nerves, leading to symptoms including tingling, weakness, and numbness that can become paralysis.^[13]

Signs of Somatic Nervous System Problems

Depending on whether the damage is to the motor nerves, which regulate movement, or the sensory nerves, which affect the senses, the symptoms of a somatic nervous system problem can differ.^[14]

Damage to the motor nerves shows as:

• Loss of movement control
• Spasms or cramps in muscles
• Tremors or twitching
• Wasting of muscles (muscle shrinkage)

The following signs could be present if the sensory system is damaged:

• Inability to feel things you touch
• Numbness or tingling
• Sharp or burning pain in the damaged area

Other animals

In

(ACh) – can only be excitatory.

See also

• Autonomic nervous system
• Enteric nervous system
• Nervous system

References